Field of the Invention This invention relates to ctia and/or a^ adrenergic receptor antagonists. Compounds disclosed herein can function as ctia and/or aid adrenergic receptor antagonists and can be used for the treatment of diseases or disorders mediated through aia and/or aid adrenergic receptors. Compounds disclosed herein can be used for the treatment of benign prostatic hyperplasia and related symptoms thereof. Compounds disclosed herein can also be used for the treatment of lower urinary tract symptoms associated with or without benign prostatic hyperplasia. The invention also relates to a process for the preparation of compounds disclosed herein, pharmaceutical compositions containing these compounds and the methods of treating diseases or disorders mediated through aja and/or aid receptors. Background of the Invention Benign prostatic hyperplasia (BPH) is a condition which develops in elderly males and refers to the benign overgrowth of the stromal and epithelial elements of the prostate associated with aging. The symptoms of BPH vary, but the most common ones involve changes or problems with urination, such as a hesitant, interrupted, weak stream or urgency and leaking or dribbling or more frequent urination, especially at night. Consequences of BPH can involve hypertrophy of bladder smooth muscle, a decompensated bladder and an increased incidence of urinary tract infection. There are two components of BPH, static and a dynamic component. The static component is due to enlargement of the prostate gland, which may result in compression of the urethra and obstruction to the flow of urine from the bladder. The dynamic component is due to increased smooth muscle tone of the bladder neck and prostate itself and is regulated by a-1 adrenergic receptor. Currently, the most effective treatment for BPH is the surgical procedure of transurethral resection of the prostate (TURP), since it removes the obstructing tissue (C. Chappie's Br. Med. Journal 304: 1198-1199, 1992). It is a treatment, which is directed to the static and dynamic components of the BPH. However this surgical treatment is associated with rates of mortality (1%) and adverse event (incontinence 2-4%) infection 5-10 %, and impotence 5-10%. A non invasive alternative treatment is therefore highly desirable. There are some drug therapies, which address the static component of this condition. Administration of finasteride is one such therapy, which is indicated for the treatment of symptomatic BPH. This drug is a competitive inhibitor of the enzyme 5a-reductase which is responsible for the conversion of testosterone to dihydrotestosterone in the prostate gland. Dihydrotestosterone appears to be the major mitogen for prostate growth, and agents which inhibit 5a reductase reduce the size of the prostate and improve urine flow through the prostatic urethra. Although finasteride is a potent 5a reductase inhibitor and causes a marked decrease in serum and tissue concentrations of dihydrotestosterone, it is only moderately effective in the treatment of symptomatic BPH. The effects of finasteride take 6-12 months to become evident, and for many men the clinical development is minimal. The dynamic component of BPH has been addressed by the use of adrenergic receptor blocking agents, which act by decreasing the smooth muscle tone within the prostate gland. A variety of o,\ adrenergic receptor antagonists such as terazosin, doxazosin, prazosin, alfuzosin and tamulosin have been investigated for the treatment of symptomatic bladder outlet obstruction due to BPH. However, these drugs are associated with vascular side effects (e.g. postural hypertention, syncope, dizziness, headache etc) due to lack of selectivity of action between prostatic and vascular ai-adrenoceptors. There are several lines of evidence to suggest that selectivity for aia adrenoceptor over aib adrenoceptor will result in relative lack of vascular side effects, thus lead to a better tolerability. In-vivo studies in healthy subjects comparison of ctia/aid selective antagonists (e.g., tamsulosin) or a\a selective antagonists (e.g., urapidil) with non selective antagonists (e.g., doxazosin, prazosin, or terazosin) under a variety of experimental conditions (e.g., involving the administration of exogenous agonist or release of endogenous agonist by cold stimulation) in several vascular beds including the skin circulation in finger tips, the dorsal hand vein, or with total peripheral resistance have been reported. (Eur. J. Clin. Pharmacol, 1996, 49, 371-375; Naunyn Schmiedeberg's Arch. Pharmacol 1996, 354, 557-561; Jpn. J. Pharmacol. 1999, 80, 209-215; Br J. Clin. Pharmacol. 1999, 47, 67-74).. These studies have reported that an antagonist with high affinity for aia or aia/aia can cause some degree of vasodilation but that it is much smaller than with non-subtype-selective o,\ adrenoceptor antagonist. Further, there is increased vascular aib adrenoceptor expression in elderly patients and thus aia/aid selective agents with selectivity over a^ adrenoceptor subtype would be of particular importance in benign prostatic hyperplasia, which is generally a disease of old age. Antagonism of both dia adrenoceptor and a^ adrenoceptor is believed important to relieve lower urinary tract symptoms especially associated (suggestive of) with BPH. Targeting aia adrenoceptor with antagonists is important in relaxing prostate smooth muscle and relieving bladder outlet obstruction whereas aid adrenoceptor antagonism is important to target irritative symptoms. Over the past decade, there has been an intensive search for selective a.\ adrenoceptor antagonists for benign prostatic hyperplasia which would avoid the cardiovascular side effects associated with currently used drugs. Selective antagonists have been described by Hieble et al in Exp. Opin. Invest. Drugs; 6, 367-387 (1997) and by Kenny et al., in J. Med. Chem.; 40, 1293-1325 (1995). Pharmacological activities associated with phenyl piperazines have been studied in, Eur. J. Med. Chem. - Chimica Therapeuticct, 12, 173-176 (1977), which describes substituted trifluorometyl phenyl piperazines having cyclo-imido alkyl side chains shown below. . These compounds are potential anorectic agents with no CNS side effects. Other compounds which have been prepared as anxiolytic, neuroleptic, anti-diabetic and anti-allergic agents are described in the following references: Yukihiro et al; PCX Appl. WO 98/37893 (1998), Steen et al; J. Med. Chem., 38, 4303-4308 (1995), Ishizumi et al. Chem. Pharm. Bull; 39 (9), 2288-2300 (1991), Kitaro et al; JP 02-235865 (1990), Ishizumi et al; U.S. Patent No. 4,598,078 (1986), New et. al; /. Med. Chem. 29, 1476-1482 (1986), Shigeru et. al; JP 60-204784 (1985), New et al, U.S. Patent No. 4,524, 206 (1985), Korgaonkar et al; J. Indian Chem. Soc., 60,874-876(1983). The synthesis and pharmacology of some 2-[3-(4-aryl-l-piperazinyl) propyl]-lH-benz(de) isoquinolin-l,3-(2H)-diones/2,5-pyrrolidinediones (J. Indian. Chem. Soc., Vol., LXIII, 529-530 (1986), of N-(N4-aryl-N1-piperozinylmethyl)-4-(4-methoxyphenyl)piperidine-2,6-diones [J. Indian Chem. Soc., Vol. LV, 819-821 (1978)], and of N-(N4-arylpiperazinylalkyl)-phthalimides (J. Indian. Chem. Soc., Vol. LVI, 1002-1005 (1979)] have been reported. The compounds were shown to exhibit antihypertensive and CNS depressant activity in experimental animals.However, none of the above mentioned references disclose or suggest the cci subtype selectivity profile of the compounds disclosed therein and thus their usefulness in the treatment of symptoms of benign prostate hyperplasia did not arise. The synthesis of l-(4-arylpiperazin-l-yl)-co-[N-(a, co-dicarboximido)]-alkanes useful as uro-selective cti-adrenoceptor blockers are disclosed in U.S. Patent Nos. 6,083,950, 6,090,809, 6,410,735, 6,420,559 and 6,420,366. These compounds have good ai-adrenergic blocking activity and selectivity. Other reports describing selective cii adrenoceptor antagonists are U.S. Patent Nos. 6,376,503, 6,319,932, and 6,339,090, EP 711757, WO 02/44151; 99/42448, 99/42445, 98/57940, 98/57632, 98/30560 and WO 97/23462, and all these patents are incorporated by reference herein in their entirety. Summary of the Invention Provided herein are aia and/or aid adrenergic receptor antagonists which are useful as safe and effective treatment of benign prostatic hyperplasia or related symptoms thereof, and method for the syntheses of these compounds. Also provided herein are pharmaceutical compositions containing the compounds, which may also contain pharmaceutically acceptable carriers, excipients or diluents which are useful for the treatment of benign prostatic hyperplasia or related symptoms thereof. Also provided herein are the enantiomers, diastereomers, pharmaceutically acceptable salts pharmaceutically acceptable, solvates, polymorphs, N-oxides or metabolites of these compounds having the same type of activity. Pharmaceutical compositions comprising the compounds of the invention, their enantiomers, diastereomers, polymorphs, pharmaceutically acceptable salts, pharmaceutically acceptable solvates, N-oxides or metabolites, in combination with pharmaceutically acceptable carriers and optionally included excipients are also provided herein. Other aspects will be set forth in the description which follows, and in part will be apparent from the description or may be learnt by the practice of the invention. In accordance with one aspect of the present invention, there is provided a compound having the structure of Formula I, (Figure Remove) N — R Formula I pharmaceutically acceptable acid addition salts, solvates, enantiomers, diastereomers, regioisomers, N-oxides, polymorphs, prodrugs or metabolites thereof, wherein: Ri can be alkyl, cycloalkyl or R3N(R4)(CH2)m; R2 can be hydrogen, alkyl, cycloalkyl or R3N(R4)(CH2)m; m can be an integer 0 or 1 ; Ra can be alkyl or cycloalkyl; can be alkyl or cycloalkyl; can be hydrogen, halogen or alkyl; R4 can be hydrogen or alkyl; RI and R2 together can form cycloalkyl or cycloalkenyl; (Figure Remove) ^^ can be optional double bond; n can be an integer of from 1 to 2. In accordance with a second aspect, there is provided a method for the treatment of a patient suffering from a disease or disorder mediated through ctia and/or aid adrenergic receptor, comprising administering to a patient in need thereof, an effective amount of adrenergic receptor antagonist. In accordance with a third aspect, there is provided a method for the treatment of a patient suffering from benign prostatic hyperplasia and related symptoms, comprising administering to a patient in need thereof, an effective amount of adrenergic receptor antagonist compounds as described above. In accordance with a fourth aspect, there is provided a method for the treatment of a patient suffering from lower urinary tract symptoms, for example, irritative symptoms such as frequent urination, urgent urination, nocturia and unstable bladder contractions, obstructive symptoms such as hesitancy, poor stream, prolong urination, and feelings of incomplete emptying, comprising administering to a patient in need thereof, an effective amount of adrenergic receptor antagonist compounds as described above. In accordance with a fifth aspect, there are provided processes for preparing the compounds as described above. In accordance with a sixth aspect, there is provided a method for the treatment of a patient suffering from benign prostatic hyperplasia and related symptoms, comprising administering to a patient in need thereof, an effective amount of a compound (or composition) described above in combination with a selective muscarinic receptor antagonist. In accordance with a seventh aspect, there is provided a method for the treatment of a patient suffering from benign prostatic hyperplasia and related symptoms, comprising administering to a patient in need thereof, an effective amount of a compound (or composition) described above in combination with and a testosterone 53-Tetrafluoro-propoxy)-phenyl]-piperazin-l-yl}-propyl)- 3-cyclobutylamino-methyl-pyrrolidine-2,5-dione (Compound No. 131) and its hydrochloride salt (Compound No. 132) l-{3-[4-(3-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrolidine-2,5-dione (Compound No. 133) and its hydrochloride salt (Compound No. 134) 5-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-5-aza-spiro[2.4] heptane-4,6-dione (Compound No. 135) and its hydrochloride salt (Compound No. 136) l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-methylaminomethyl-pyrrolidine-2,5-dione (Compound No. 137) and its hydrochloride salt (Compound No. 138) 1 - {3-[4-(2-Cyclopropylmethoxy-phenyl)-piperazin-1 -yl] -propyl} -3-cyclopropylamino-methyl-pyrrolidine-2,5-dione (Compound No. 139) and its hydrochloride salt (Compound No. 140) l-{3-[4-(2-Cyclopropylmethoxy-phenyl)-piperazin-l-yl]-propyl}-3-methylamino-methyl-pyrrolidine-2,5-dione (Compound No. 141) and its hydrochloride salt (Compound No. 142) l-{3-[4-(2-Cyclopropylmethoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrolidine-2,5-dione (Compound No. 143) and its hydrochloride salt (Compound No. 144) l-{3-[4-(2-Methoxy-phenyl)-piperazin-l-yl]-propyl}-3-methylaminomethyl-pyrrolidine-2,5-dione (Compound No. 145) and its hydrochloride salt (Compound No. 146) 1 - {3-[4-(2-Cyclopentyloxy-phenyl)-piperazin-1 -yl]-propyl} -3-cyclopropylaminomethyl-pyrrolidine-2,5-dione (Compound No. 147) and its hydrochloride salt (Compound No. 148) 1 - {3 - [4-(2-Cyclopentyloxy-phenyl)-piperazin-1 -yl] -propyl} -3 -(isopropylamino-methyl)-pyrrolidine-2,5-dione (Compound No. 149) and its hydrochloride salt (Compound No. 150) 5 - {3 - [4-(2-Cyclopentyloxy-phenyl)-piperazin-1 -yl] -propyl} -5 -aza-spiro [2.4]heptane- 4,6-dione (Compound No. 151) and its hydrochloride salt (Compound No. 152) 1 - {3-[4-(3 -Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -(isopropylamino-methyl)-pyrrolidine-2,5-dione (Compound No. 153) and its hydrochloride salt (Compound No. 154) 1 - {3 - [4-(3 -Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -cyclopropylamino-methyl-pyrrolidine-2,5-dione (Compound No. 155) and its hydrochloride salt (Compound No. 156) 5- {3 - [4-(3-Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -5 -aza-spiro [2.4] heptane- 4,6-dione (Compound No. 157) and its hydrochloride salt (Compound No. 158) 1 - {3-[4-(5 -Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -cyclopropylamino-methyl-pyrrolidine-2,5-dione (Compound No. 159) and its hydrochloride salt (Compound No. 160) l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-(isopropylamino-methyl)-pyrrolidine-2,5-dione (Compound No. 161) and its hydrochloride salt (Compound No. 162) l-{3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-l-yl]-propyl}-3-[(cyclopropyl-methyl-amino)-methyl]-pyrrolidine-2,5-dione (Compound No. 163) and its hydrochloride salt (Compound No. 164) 1 - {3 - [4-(2-Cyclopentyloxy-5 -fluoro-phenyl)-piperazin-1 -yl] -propyl} -3 -isopropylamino-methyl)-pyrrolidine-2,5-dione (Compound No. 165) and its hydrochloride salt (Compound No. 166) 1 - {3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-1 -yl] -propyl} -3 -cyclopropylaminomethyl-pyrrolidine-2,5-dione (Compound No. 167) and its hydrochloride salt (Compound No. 168) 1 - {3 - [4-(2-Cyclopentyloxy-5 -fluoro-phenyl)-piperazin-1 -yl] -propyl} -3 -methyl-pyrrolidine-2,5 -dione (Compound No. 169) and its hydrochloride salt (Compound No. 170) l-{3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrole-2,5-dione (Compound No. 171) and its hydrochloride salt (Compound No. 172) l-{3-[4-(2-Methoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-4-prop-2-ynylamino-pyrrolidine-2,5-dione (Compound No. 173) and its hydrochloride salt (Compound No. 174) 1 - {3 - [4-(4-Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 - [(cyclopropyl-niethyl-aminoVmethy^-pyrrolidine^S-dione (Compound No. 175) and its hydrochloride salt (Compound No. 176) 1 - {3- [4-(2-Methoxy-phenyl)-piperazin-1 -yl] -propyl} -3- [(cyclopropyl-methyl-amino)-methyl] -pyrrolidine-2,5-dione (Compound No. 177) and its hydrochloride salt (Compound No. 178) 1 -(3-{4-(2-(2,2,2-Trifluoro-ethoxy)-phenyl]-piperazin-1 -yl} -propyl)- 3-[(cyclopropyl-methyl-amino)-methyl]-pyrrolidine-2,5-dione (Compound No. 179) and its hydrochloride salt (Compound No. 180) l-{3-[4-(2-Methoxy-phenyl)-piperazin-l-yl]-propyl}-3-(isopropylamino)-methyl)-pyrrolidine-2,5-dione (Compound No. 181) and its hydrochloride salt (Compound No. 182) 5-(3-{4-[2-(2,2,2-Trifluoro-ethoxy)-phenyl]-piperazin-l-yl}-propyl)-5-aza-spiro[2.4]heptane-4,6-dione (Compound No. 183) and its hydrochloride salt (Compound No. 184) l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrole-2,5-dione (Compound No. 185) and its hydrochloride salt (Compound No. 186) 1 - {3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -methyl-pyrrolidine-2,5-dione (Compound No. 187) and its hydrochloride salt (Compound No. 188) l-{3-[4-(5-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrole-2,5-dione (Compound No. 189) and its hydrochloride salt (Compound No. 190) l-{3-[4-(5-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrolidine-2,5-dione (Compound No. 191) and its hydrochloride salt (Compound No. 192) l-{3-[4-(2-Cyclopentyloxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrolidine-2,5-dione (Compound No. 193) and its hydrochloride salt (Compound No. 194) l-{3-[4-(3-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrole-2,5-dione (Compound No. 195) and its hydrochloride salt (Compound No. 196) 1 - {3- [4-(3 -Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -methyl-pyrrolidine-2,5-dione (Compound No. 197) and its hydrochloride salt (Compound No. 198) The salts described herein may be prepared by the useful prior art techniques, such as suspending the compound in water and then adding one equivalent of an organic acid such as acetic acid, oxalic acid, maleic acid, tartaric acid, citric acid, succinic acid, malonic acid, adipic acid, ascorbic acid, camphoenic acid, nicotinic acid, butyric acid, lactic acid, glucuronic acid, or inorganic acids such as hydrochloric acid, hydrobromic acid, phosphoric acid, sulfuric acid, nitric acid, boric acid and perchloric acid. The neutral solution of the resulting salt is subjected to rotary evaporation under diminished presence to the volume necessary to ensure precipitation of the salt upon cooling, which is then filtered and dried. The salts of the present invention may also be prepared under strictly non-aqueous conditions. For example, dissolving free base in an organic solvent such as ethanol, methanol, isopropanol, dichloromethane or diethyl ether adding exactly one equivalent of the desired acid to the same solvent and stirring the solution at 0°C to 5°C, causes the precipitation of the acid addition salt, which is then filtered, washed free from the solvent, and dried. Alternatively, the solvent is stripped completely to obtain the desired salt. These salts are often preferred for use in formulating the therapeutic composition of the invention because they are crystalline and relatively more stable and water soluble. The compounds described herein have got pharmacological activity, therefore may be administered to an animal for treatment orally, topically, rectally, internasally, or by parenteral route. The pharmaceutical compositions of the present invention comprise a pharmaceutically effective amount of a compound of the present invention formulated together with one or more pharmaceutically acceptable carriers. The term "pharmaceutically acceptable carriers" includes non-toxic, inert solid, semi-solid or liquid filter, diluent, encapsulating material or formulation auxiliary of any type. Solid form preparations for oral administration, include capsules, tablets, pills, powders, granules cathets and suppositories. For solid form preparations, the active compound is mixed with at least one inert, pharmaceutically acceptable excipient or carrier such as sodium citrate, dicalcium phosphate and/or a filler or extenders such as starch, lactose, sucrose, glucose, mannitol and silicic acid; binders such as carboxymethylcellulose, alginates, gelatins, polyvinylpyrolidinone, sucrose, acacia; disintegrating agents such as a agar-agar, calcium carbonate, potato starch, alginic acid, certain silicates and sodium carbonate, absorption accelators such as quaternary ammonium compounds; wetting agents such as cetyl alcohol, glycerol, monostearate; adsorbents such as kaolin; lubricants such as talc, calcium stearate, magnesium stearate, solid polyethyleneglycol, sodium lauryl sulphate and mixture thereof. In the case of capsules, tablets, or pills, the dosage form may also comprise buffering agents. The solid preparation of tablets, capsules, pills, granules can be prepared with coating and shells such as enteric coating and other coatings well known in the pharmaceutical formulating art. Liquid form preparations for oral administration include pharmaceutically acceptable emulsions, solution, suspensions, syrups and elixirs. For liquid form preparations, the active compound can be mixed with water or other solvent, solubilizing agents and emulsifiers such as ethyl alcohol, isopropyl alcohol, ethyl carbonate, ethyl acetate, benzyl alcohol, benzyl benzoate, propylene glycol, 1,3-butylene glycol, dimethylformamide, oils (such as cottonseed, groundnut, corn, germ, olive, castor and Sesamie oil), glycerol, and fatty acid esters of sorbitan and mixture thereof. Besides inert diluents, the oral composition can also include adjuvant such as wetting agents, emulsifying agents, suspending agents, sweetening agents, flavoring agents and perfuming agents. Injectable preparations such as sterile injections, aqueous or oleaginous suspensions may be formulated according to the art using suitable dispersing or wetting and suspending agents. Among the acceptable vehicles and solvents that may be employed are water, Ringer's solution, U.S.P. and isotonic sodium chloride. Dosage forms for tropical or transdermal administration of compounds provided herein include ointments, pastes, creams, lotions, gel, powders, solutions, spray, inhalants or patches. The active compound is admixed under sterile condition with a pharmaceutically acceptable carrier and any needed preservative or buffer as may be required. Ophthalmic formulation, eardrops, eye ointments, powder and solution are also provided. The pharmaceutical preparation may be in unit dosage form. In such form, the preparation may be subdivided into unit doses containing appropriate quantities of the active component. The unit dosage form can be a packaged preparation, the package containing discrete capsules, powders, in vials or ampoules and ointments, capsules, cachet, tablet, gel cream itself or it can be the appropriate number of any of their packaged forms. The formulation of the present invention may be formulated so as to provide quick, sustained, or delayed release of the active ingredient after administration to the patient by employing procedures well known to the art. The dosages of the compounds described herein, muscarinic receptor antagonists and 5 a-reductase inhibitors are adjusted when combined to achieve desired effects. As those skilled in the art will appreciate, dosages of the compounds described herein, muscarinic receptor antagonist and 5 a-reductase inhibitor may be independently optimized and combined to achieve a synergistic result wherein the pathology is reduced more than it would be if either agent were used alone. In accordance with methods provided herein, the individual components of combinations can be administered separately at different times during the course of therapy or concurrently in divided or single combination forms. The examples mentioned below demonstrate general synthetic procedures for the preparation of representative compounds. The examples are provided to illustrate particular aspect of the disclosure and do not limit the scope of the present invention as defined by the claims. Experimental details Example 1: Preparation of l-(3-[4-(5-Fluoro-2-isopropoxy-phenylVpiperazin-l-vl1-propvU-3-methyl-pvrrole-2,5-dione hydrochloride salt (Compound No. 186) Step 1: Preparation of 3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propionitrile To a solution of l-(5-Fluoro-2-isopropoxyphenyl)-piperazine (5gm, 0.021 mol) in methanol (25ml) was added acrylonitrile (1.34 gm, 0.025mol) under stirring at room temperature. The reaction mixture was stirred for about 3 to 4 hours. After completion of the reaction, the reaction mass was concentrated on buchi to yield the desired product. Yield: 6 gm, (98%). Step 2: Preparation of 3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propylamine To a solution of 3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propionitrile (5 gm, 0.017 mol) in methanol-ammonia (20 ml) was added Palladium-Carbon (10% w/w of 3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propionitrile) and the reaction mixture was hydrogenated at 55 to 60 psi for about 4 to 5 hours. After completion of the reaction, the reaction mixture was filtered through celite pad, washed with methanol; filtrate thus obtained was concentrated to yield the required compound. Yield: 5 gm, (98%). Step 3: Preparation of 1 -{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl]-propyl}-3-methyl-pyrrole-2, 5-dione A solution of 3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propylamine (1 gm, 0.0034 mol) and citraconic anhydride (0.38 gm, 0.0034 mol) in toluene (15 ml) was refluxed for about 1 hour. The reaction mixture was concentrated to yield the crude product which was purified on the column of silica gel (60-120 mesh) using dichloromethane-methanol mixture as eluent. Yield: 1 gm, (77%). Step 4: Preparation of l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrole-2, 5-dione hydrochloride salt An equimolar quantity of isopropyl alcohol-hydrochloric acid was added to l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrole-2, 5-dione and the resulting salt was solidified by adding ether to it. IR: 1706.5 cm'1; 'HNMR (300 MHz, CDC13)6: 1.47-1.53 (6H, d), 2.08 (3H, s), 2.25 (2H, s), 3.17 (2H, s), 3.17 (2H, s), 3.64-3.66 (6H, d), 4.06 (2H, s), 4.06-4.69 (5H, m), 6.35 (1H, m), 6.93-7.73 (3H, m); Mass (m/z): 390 (M++l). The following compounds were prepared similarly. Compound No. 172: l-{3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrole-2,5-dione hydrochloride salt. Compound No. 190: l-{3-[4-(5-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrole-2,5-dione hydrochloride salt. IR (KBr): 1708.3 cm'1; *HNMR (300 MHz, CDC13)8: 2.10 (3H, s), 2.27-2.33 (2H, t), 3.04 (4H, s), 3.51-3.67 (8H, m), 3.83 (3H, s), 6.36 (1H, s), 6.36-6.79 (3H, m); Mass (m/z): 362.3 (M++l). Compound No. 196: l-{3-[4-(3-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrole-2,5-dione hydrochloride salt. 'HNMR (300 MHz, CDC13)8: 2.11 (3H, s), 2.29 (2H, s), 3.12 (2H, s), 3.59-3.67 (8H, m), 4.09 (3H, s), 4.22 (2H, s), 6.37 (1H, s), 7.00-7.05 (3H, m); Mass (m/z): 362 (M++l). Example 2: Preparation of l-(3-[4-(5-Fluoro-2-isopropoxy-phenvD-piperazin-l-yl]-propyll-3-cyclopropvlamino-4-methvl-pvrrolidine-2, 5-dione hydrochloride salt (Compound No.76) Step 1: Preparation of l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylamino-4-methyl-pyrrolidine-2, 5-dione To a solution of l-{ 3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrole-2,5-dione (0.5 gm, 0.0013 mol) in methanol was added equimolar quantity of cyclopropylamine (0.073 gm, 0.0013 mol) and the reaction mixture was stirred at room temperature for about 10 to 12 hours. The reaction mixture was concentrated to yield the crude product which was then purified on a column of silica gel (60-120 mesh) using dichloromethane- methanol mixture as eluent. Yield: 0.256 gm, (45%). Step 2: Preparation of l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylamino-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt An equimolar quantity of isopropyl alcohol-hydrochloric acid was added to .l.{3_[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylamino 4-methyl-pyrrolidine-2, 5-dione and the resulting salt was solidified by adding ether to it. 'HNMR (300 MHz, CDC13)8: 0.59 (4H, s), 1.11-1.45 (6H, m), 1.53 (3H, s), 2.15 (1H, s),2.27 (1H, s), 2.61-2.67 (1H, d), 3.17-3.29 (6H, t), 3.48 (5H, s), 3.69 (3H, s), 4.45-4.53 (1H, m), 6.62-6.80 (3H, m); Mass (m/z): 447 (M++l). The following compounds were prepared similarly. Compound No. 2: l-{3-[4-(5-Fluoro-2-propoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-4-methylamino-pyrrolidine-2, 5-dione hydrochloride salt. 'HNMR (300 MHz, CDC13)8: 1.02-1.07 (3H, t), 1.35-1.38 (3H, t), 1.30-1.87 (2H, q), 2.23-2.27 (2H, t), 2.34-2.39 (1H, d), 2.95-3.03 (6H, m), 3.51 (5H, s), 3.61-3.69 (2H, m), 3.90-3.94 (2H, m), 6.62-6.79 (3H, m); Mass (m/z): 392 (M++l). Compound No. 6: l-{3-[4-(5-Fluoro-2-propoxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylamino- 4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. 'HNMR (300 MHz, CDC13)6: 0.658-0.881 (5H, m), 1.008-1.057 (3H, t), 1.785-1.854 (3H, m), 2.289 (4H, s), 2.655-2.715 (2H, d), 3.250-3.507 (13H, m), 3.888-3.931 (2H, t), 6.625-6.789 (3H, m); Mass (m/z): 447 (M++l). Compound No. 12: l-{3-[4-(2-Methoxy-5-methyl-phenyl)-piperazin-l-yl]-propyl}-3-methyl-4-methylamino-pyrrolidine-2, 5-dione hydrochloride salt. IR (KBr): 1714.9 cm'1; Mass: 389 (M++l). Compound No. 14: l-{3-[4-(2-Methoxy-5-methyl-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylamino-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. IR (KBr): 1700.2 cm'1; Mass (m/z): 415 (M++l). Compound No. 16: l-{3-[4-(5-Fluoro-2-propoxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclobutylamino-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. IR (KBr): 1713.1 cm'1; Mass (m/z): 461.36 (M++l). Compound No. 18: l-(3-{4-[5-Fluoro-2-(2, 2, 2-trifluoro-ethoxy)-phenyl]-piperazin-l-yl}-propyl)- 3-cyclopropylamino-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. IR (KBr): 1716 cm'1; Mass (m/z): 487 (M++l). Compound No. 20: l-(3-{4-[5-Fluoro-2-(2,2,2-trifluoro-ethoxy)-phenyl]-piperazin-l-yl}-propyl)-3-methyl-4-methylamino-pyrrolidine-2,5-dione hydrochloride salt. IR (KBr): 1716.6 cm'1; Mass (m/z): 461.25 (M++l). Compound No. 26: l-(3-{4-[2-(2,2,3,3-Tetrafluoro-propoxy)-phenyl]-piperazin-l-yl}-propyl)-3-cyclopropylamino-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. IR (KBr): 1704.1 cm'1; Mass (m/z): 501 (M++l). Compound No. 28: l-(3-{4-[2-(2,2,3,3-Tetrafluoro-propoxy)-phenyl]-piperazin-l-yl}-propyl)-3-cyclobutylamino-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. IR (DCM): 1713.8 cm'1; Mass (m/z): 515 (M++l). Compound No. 30: l-{3-[4-(2-Cyclopentyloxy-phenyl)-piperazm-l-yl]-propyl}-3-cyclobutylamino-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. IR (KBr): 1704.5 cm'1; Mass (m/z): 469 (M++l). Compound No. 34: l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-4-methylamino-pyrrolidine-2, 5-dione hydrochloride salt. IR (KBr): 1714 cm"1; Mass (m/z): 421 (M++l). Compound No. 36: l-{3-[4-(5-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-4-methylamino-pyrrolidine-2, 5-dione hydrochloride salt. IR (KBr): 1695.3 cm"1; Mass (m/z): 393 (M++l). Compound No. 44: l-{3-[4-(2-Cyclopropylmethoxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylamino-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. 'HNMR (300 MHz, DMSO)5: 0.33-0.35 (2H, d), 0.57-0.59 (2H, d), 0.69 (5H, s), 1.10 (1H, s), 1.24-1.25 (2H, d), 1.57 (3H, s), 2.60-2.65 (2H, d), 2.87-3.56 (15H, m), 6.93-7.01 (4H, m); Mass (m/z): 441 (M++l). Compound No. 48: l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclobutylamino-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. IR (KBr): 1707 cm"1; Mass (m/z): 461 (M++l). Compound No. 50: l-{3-[4-(3-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-4-methylamino-pyrrolidine-2,5-dione hydrochloride salt. IR (KBr): 1703 cm'1; Mass (m/z): 421 (M++l). Compound No. 52: l-{3-[4-(2-Cyclopropylmethoxy-phenyl)-piperazin-l-yl]-propyl}-3-isopropylamino-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. 'HNMR (300 MHz, DMSO)5: 0.33-0.58 (5H, m), 1.24-1.37 (11H, m), 1.65 (2H, s), 2.05-2.07 (2H, d), 2.95-3.17 (8H, m), 3.83-3.86 (3H, d), 6.88-6.97 (4H, m); Mass (m/z): 443.52 (M++l). Compound No. 56: l-{3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylamino-4-methyl-pyrrolidine-2,5-dione hydrochloride salt. Compound No. 58: l-{3-[4-(5-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3-(cyclopropylmethyl-amino)-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. IR (KBr): 1704.2 cm"1; Mass (m/z): 433 (M++l). Compound No. 60: l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-(cyclopropylmethyl-amino)-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. IR (KBr): 1688.7 cm'1; Mass (m/z): 461 (M++l). Compound No. 62: l-{3-[4-(5-Fluoro-2-trifluoromethoxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylamino-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. IR (KBr): 1704.1 cm'1; Mass (m/z): 455 (M++l). Compound No. 64: l-{3-[4-(2-Methoxy-phenyl)-piperazin-l-yl]-propyl}-3-(cyclopropylmethyl-amino)-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. IR (KBr): 1695.1 cm'1; Mass (m/z): 415 (M++l). Compound No. 66: l-{3-[4-(2-Isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-isopropylamino-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. IR: 1707.4 cm'1; Mass (m/z): 430 (M++l). Compound No. 68: l-{3-[4-(2-Isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylamino-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. IR: 1695.6 cm'1; Mass: 428 (M++l). Compound No. 70: l-{3-[4-(2-Methoxy-phenyl)-piperazin-l-yl]-propyl}-3-isopropylamino-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. IR: 1715.2 cm'1; Mass: 402 (M++l). Compound No. 78: l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-isopropylamino-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. 'HNMR (300 MHz, CDC13)8: 1.209-1.368 (6H, m), 1.415-1.547 (3H, t), 1.638-1.655 (3H, d), 1.748 (4H, s), 2.401 (2H, s), 2.721-2.779 (1H, d), 2.779-3.343 (4H, brs), 3.446-3.991 (10H, m), 4.411-4.469 (1H, q), 6.567-6.782 (3H, m); Mass (m/z): 449 (M++l). Compound No. 80: l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-(cyclopropyl-methyl-amino)-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. IR (KBr): 1715.1 cm'1; 'HNMR (300 MHz, DMSO)8: 0.831-0.853 (4H, d), 1.257-1.276 (6H, d), 1.691 (3H, s), 2.018 (2H, s), 2.775 (3H, s), 2.893-2.954 (3H, d), 3.163 (4H, s), 3.467-3.637 (8H, q), 4.007 (1H, s), 6.769-6.799 (3H, m); Mass (m/z): 461 (M++l). Compound No. 90: l-{3-[4-(2-Cyclopentyloxy-phenyl)-piperazin-l-yl]-propyl}-3-isopropylamino-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. IR (KBr): 1714 cm'1; Mass (m/z): 457 (M++l). Compound No. 92: l-{3-[4-(5-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylamino-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. IR (KBr): 1693.6 cm'1; 'HNMR (300 MHz, CDC13)8: 1.481 (3H, s), 2.037 (1H, s), 2.244 (2H, s), 2.575-2.635 (1H, d), 3.053 (2H, s), 3.170-3.231 (2H, d), 3.462 (6H, s), 3.656-3.699 (2H, t), 3.835 (3H, s), 6.645-6.789 (3H, m); Mass (m/z): 419.2 (M++l). Compound No. 94: l-{3-[4-(2-Cyclopentyloxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-4-methylamino-pyrrolidine-2, 5-dione hydrochloride salt. IR (KBr) : 1716.3 cm'1; 'HNMR (300 MHz, CDC13)8: 1.62-2.03 (1 1H, m), 2.36 (3H, s), 2.76-2.80 (4H, d), 3.20 (4H, s), 3.35-3.77 (9H, m), 4.76 (1H, s), 6.81-6.98 (4H, m); Mass (m/z): 492 Compound No. 102: l-{3-[4-(3-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-4-methylamino-pyrrolidine-2, 5-dione hydrochloride salt. IR (KBr): 1721 cm'1; 'HNMR (300 MHz, DMSO)6: 1.556 (3H, s), 1.981 (2H, s), 2.549 (3H, s), 2.844-3.553 (15H, m), 3.840 (3H, s), 6.799-7.079 (3H, m); Mass (m/z): 393 (M++l). Compound No. 104: l-{3-[4-(3-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylamino-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. IR (KBr): 1695.8 cm'1; 'HNMR (300 MHz, CDC13)8: 0.540-0.595 (5H, t), 1.501 (3H, s), 2.071 (1H, s), 2.250-2.271 (2H, d), 2.586-2.647 (1H, d), 3.102-3.708 (13H, m), 3.906 (3H, s), 6.670-6.960 (3H, m); Mass (m/z): 419 (M++l). Compound No. 108: l-{3-[4-(3-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylamino-4-methyl-pyrrolidine-2, 5-dione hydrochloride salt. 'HNMR (300 MHz, CDC13)5: 0.528-0.556 (4H, d), l.l 84-1.362 (9H, m), 2.062 (1H, s), 2.238 (2H, s), 2.582-2.643 (1H, d), 3.067 (4H, s), 3.187-3.248 (3H, d), 3.361 (5H, s), 3.513 (2H, s), 4.472-4.512 (1H, t), 6.667-6.983 (3H, m); Mass (m/z): 447 (M++l). Compound No. 1 74: l-{3-[4-(2-Methoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-4-prop-2-ynylamino-pyrrolidine-2, 5-dione hydrochloride salt. IR: 1701.5 cm'1; Mass: 398 (M++l). Example 3: Preparation of l-(3-[4-(5-Fluoro-2-isopropoxv-phenyl)-piperazin-l-vl]-propvU-3,4-dimethyl-pyrrole-2. 5-dione hydrochloride salt (Compound No. 72) Step 1 : Preparation of l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3,4-dimethyl-pyrrole-2, 5-dione A solution of 3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propylamine (1 gm, 0.0034 mol) and 3,4-dimethylfuran-2,5-dione (0.43 gm, 0.0034 rnol) in toluene (15 ml) was refluxed for about 1 hour. The reaction mixture was concentrated to yield the crude product which was then purified on the column of silica gel (60-120 mesh) using dichloromethane-methanol mixture as eluent. Yield: 0.8 gm, (59 %). Step 2: Preparation of l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3,4-dimethyl-pyrrole-2,5-dione hydrochloride salt An equimolar quantity of isopropyl alcohol-hydrochloric acid was added to l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3,4-dimethyl-pyrrole-2,5-dione and the resulting salt was solidified by adding ether to it. IR : 1691 cm'1; ]HNMR (300 MHz, CDC13)8: 1.25-1.33 (6H, t), 1.979 (6H, s), 2.282 (2H, s), 3.008-3.027 (4H, d), 3.536-3.660 (8H, m), 4.457-4.517 (1H, m), 6.613-6.806 (3H, m); Mass (m/z): 404 (M++l). The following compounds were prepared similarly. Compound No. 82: l-(3-{4-[2-(2,2,2-Trifluoro-ethoxy)-phenyl]-piperazin-l-yl}-propyl)- 3,4-dimethyl-pyrrole- 2,5-dione hydrochloride salt. IR (KBr): 1647 cm'1; Mass (m/z): 425 (M++l). Compound No. 86: l-{3-[4-(2-Cyclopentyloxy-phenyl)-piperazm-l-yl]-propyl}-3,4-dimethyl-pyrrole-2,5-dione hydrochloride salt. IR (KBr): 1702.4 cm'1; Mass (m/z): 412 (M++l). Compound No. 98: l-{3-[4-(3-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3,4-dimethyl-pyrrole-2,5-dione hydrochloride salt. 'HNMR (300 MHz, CDC13)6: 1.992 (6H, s), 2.206 (2H, s), 3.155-3.207 (2H, t), 3.479-3.517 (2H, d), 3.632-3.671 (6H, t), 3.818-3.859 (2H, d), 4.039-4.071 (3H, d), 6.990-7.075 (4H, m); Mass (m/z): 376 (M++l). Example 4: Preparation of 2-(3-[4-(2-Cvclopentvloxv-5-fluoro-phenvl)-piperazin-l-yl]-propyU - 3a.4JJa-tetranvdro -isoindole-1,3-dione hydrochloride salt (Compound No. 42) Step 1 Preparation of 2-(3-Chloropropyl)-3a, 4, 7, 7a-tetrahydro-isoindole-1, 3-dione Step 2: Preparation of 2-{3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-l-yl]-propyl}-3a,4,7,7a-tetrahydro-isoindole-l,3-dione A suspension of 2-(3-Chloropropyl)-3a, 4, 7, 7a-tetrahydro-isoindole-l, 3-dione (1 gin, 0.0044 mol), l-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazine (0.9 gm, 0.0037 mol), anhydrous potassium carbonate (1.2 gm, 0.0087 mol) and potassium iodide (0.014 gm, 0.00008 mol) was heated in dimethylformamide (15 ml) at 70-75 °C for about 6-8 hours. Reaction was quenched by adding water (45ml) to it; extracted with ethyl acetate. The organic layers were combined and dried over anhydrous sodium sulphate and concentrated to yield the crude product. It was then purified on a column of silica gel (60-120 mesh) using dichloromethane - methanol mixture as eluent. Yield: 1.5 gm, (75%). Step 3: 2-{3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-l-yl]-propyl} - 3a,4,7,7a-tetrahydro -isoindole-1,3-dione hydrochloride salt An equimolar quantity of isopropyl alcohol-hydrochloric acid was added to 2-{3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-l-yl]-propyl} - 3a,4,7,7a-tetrahydro -isoindole-l,3-dione and the resulting salt was solidified by adding ether to it. IR (KBr): 1700.2 cm'1; 'HNMR (300 MHz, CDC13)5: 1.70-1.74 (8H, m), 1.85-1.91 (4H, d), 2.21-2.25 (2H, d), 2.95 (4H, s), 3.16-3.17 (2H, d), 3.51-3.64 (8H, m), 4.75 (1H, s), 5.92-5.94 (2H, t), 6.61-6.76 (3H, m); Mass (m/z): 456 (M++l). The following compounds were prepared similarly Compound No. 46: 2-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3a,4,7,7a-tetrahydro-isoindole-l,3-dione hydrochloride salt. IR (KBr): 1692.8 cm'1; 'HNMR (300 MHz, CDC13)6: 1.32-1.34 (6H, d), 2.21-2.26 (4H, q), 2.61-2.66 (2H, d), 2.94-3.00 (4H, m), 3.16 (2H, s), 3.47-3.64 (8H, m), 4.48-4.50 (1H, d), 5.92-5.53 (2H, d), 6.61-6.78 (3H, m); Mass (m/z): 430 (M++l). Compound No. 110: 2-(3-{4-[2-(2,2,3,3-Tetrafluoro-propoxy)-phenyl]-piperazin-l-yl}-propyl)-3a,4,7,7a-tetrahydro-isoindole-l,3-dione hydrochloride salt. IR: 1698.8 cm'1; 'HNMR (300 MHz, CDC13)6: 2.21-2.25 (4H, m), 2.62-2.67 (2H, d), 3.00-3.17 (6H, m), 3.46-3.74 (8H, m), 4.39-4.48 (2H, m), 5.94-6.11 (3H, m), 6.90-7.13 (4H, m), 13.00 (1H, brs); Mass (m/z): 484.1 (M++l). Compound No. 112: 2-{4-[4-[2-Isopropoxy-phenyl]-piperazin-l-yl]-butyl}-3a,4,7 Ja-tetrahydro-isoindole-l,3-dione hydrochloride salt. IR (KBr): 1699.4 cm-'; 'HNMR (300 MHz, CDC13)8: 1.35-1.37 (6H, d), 1.68 (2H, m), 1.91 (2H, m), 2.20-2.25 (2H, d), 2.59-2.64 (2H, d), 3.03 (4H, m), 3.17 (2H, m), 3.53 (8H, m), 4.57-4.61 (1H, m), 5.91 (2H, brs), 6.85-7.03 (4H, m), 12.58 (1H, brs); Mass (m/z): 425.9 (M++l). Compound No. 114: 2-{3-[4-(4-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3a,4,7,7a-tetrahydro-isoindole-l,3-dione hydrochloride salt. IR (KBr): 1695.7 cm'1; 'HNMR (300 MHz, CDC13)8: 2.21-2.25 (4H, m), 2.61-2.66 (2H, dd), 2.98 (4H, brs), 3.17 (2H, brs), 3.39-3.76 (8H, m), 3.85 (3H, s), 5.93 (2H, brs), 6.61-6.64 (3H, d), 6.88 (1H, m), 12.75 (1H, brs); Mass (m/z): 402 (M++l). Compound No. 116: 2-(3-{4-[4-Fluoro-2-(2,2,2-trifluoro-ethoxy)-phenyl]-piperazin-l-yl}-propyl)-3a,4,7,7a-tetrahydro-isoindole-l,3-dione hydrochloride salt. IR (KBr): 1697.3 cm'1; 'HNMR (300 MHz, DMSO-d6)5: 1.91 (2H, m), 2.18-2.22 (2H, m), 2.38-2.43 (2H, m), 2.96-3.35 (14H, m), 4.75 (2H, m), 5.89 (2H, brs), 6.83-6.88 (1H, m), 7.00-7.07 (2H, m), 10.28 (1H, brs); Mass (m/z): 470.0 (M++l). Compound No. 118: 2-{3-[4-(4-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3a,4,7,7a-tetrahydro-isoindole-l,3-dione hydrochloride salt. IR (KBr): 1696.5 cm-'; 'HNMR (300 MHz, DMSO-d6)8: 1.27-1.29 (6H, d), 1.88-1.90 (2H, m), 2.18-2.23 (2H, m), 2.37-2.43 (2H, m), 2.89-3.17 (12H, m), 4.63-4.67 (1H, m), 5.86-5.89 (2H, d), 6.66-6.72 (1H, m),,6.88-6.94 (2H, m), 10.18 (1H, brs); Mass (m/z): 418.0 (M++l)^ Example 5: Preparation of 1 -13 - [4-(5 -Fluoro-2-isopropoxv-phenyl)-piperazin-1 -yl] -propyl} -3,4-dimethyl-pyrrolidine-2,5-dione hydrochloride salt (Compound No. 74) Stepl: Preparation of l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3,4-dimethy 1-pyrrolidine -2,5 -dione A mixture of l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3,4-dimethyl-pyrrole-2,5-dione (0.5 gm, 0.0012 mol) and palladium-carbon (0.5 gm) in methanol was hydrogenated at 45 to 50 psi for about 1 hour. The reaction mixture was concentrated to yield the desired product. Yield: 0.5 gm, (99%). Step 2: Preparation of l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3,4-dimethyl-pyrrolidine-2,5-dione hydrochloride salt An equimolar quantity of isopropyl alcohol-hydrochloric acid was added to 1 - {3 - [4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3,4-dimethyl-pyrrolidine-2,5-dione and the resulting salt was solidified by adding ether to it. 'HNMR (300 MHz, CDC13)8: 1.18-1.44 (12H, m), 2.26 (2H, s), 3.04-3.11 (6H, d), 3.44-3.63 (8H, m), 4.47-4.55 (1H, m), 6.67-6.82 (3H, m); Mass (m/z): 406.2 (M++l). The following compounds were prepared similarly. Compound No. 4: 2-(3-{4-[2-(2,2,3,3-Tetrafluoro-propoxy)-phenyl]-piperazm-l-yl}-propyl)-hexahydro-isoindole-l,3-dione hydrochloride salt. IR (KBr): 1716.3 cm'1; Mass (m/z): 486 (M++l). Compound No. 10: l-{3-[4-(2-Methoxy-5-methyl-phenyl)-piperazin-l-yl]-propyl}-3,4-dimethyl-pyrrolidine-2,5-dione hydrochloride salt. IR (KBr): 1703.4 cm'1; Mass: 374 (M++l). Compound No. 22: l-(3-{4-[5-Fluoro-2-(2,2,2-trifluoro-ethoxy)-phenyl]-piperazin-l-yl}-propyl)-3,4-dimethyl-pyrrolidine-2,5-dione hydrochloride salt. IR (KBr): 1695.1 cm'1; Mass (m/z): 446 (M++l). Compound No. 24: l-(3-{4-[2-(2,2,3,3-Tetrafluoro-propoxy)-phenyl]-piperazin-l-yl}-propyl)-3,4-dimethyl- pyrrolidine-2,5-dione hydrochloride salt. IR (KBr): 1699 cm"1; Mass (m/z): 460 (M++l). Compound No. 32: 2-{3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-l-yl]-propyl}-hexahydro-isoindole-l,3-dione hydrochloride salt. 'HNMR (300 MHz, CDC13)5: 1.462 (5H, s), 1.891 (8H, s), 2.229-2.252 (3H, d), 2.942 (3H, s), 3.061 (2H, s), 3.509-3.560 (2H, d), 3.611-3.653 (9H, m), 4.800 (1H, s), 6.776-6.803 (3H, m); Mass (m/z): 458 (M++l). Compound No. 38: l-{3-[4-(2-Cyclopropylmethoxy-phenyl)-piperazin-l-yl]-propyl}-3,4-dimethyl-pyrrolidine-2,5-dione hydrochloride salt. 'HNMR (300 MHz, CDC13)8: 0.33-0.35 (2H, d), 0.62-0.63 (2H, d), 1.23-1.25 (7H, d), 2.01 (2H, s), 3.02-3.03 (6H, d), 3.55-3.86 (10H, m), 6.81-7.03 (4H, m). Compound No. 40: 2-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-hexahydro-isoindole-l,3-dione hydrochloride salt. IR (KBr): 1692.4 cm'1; 'HNMR (300 MHz, CDC13)6: 1.306-1.326 (6H, d), 1.438-1.456 (4H, d), 1.508 (1H, s), 1.760 (2H, s), 1.846 (2H, s), 2.006-2.034 (2H, d), 2.796 (2H, s), 2.898 (4H, s), 3.317 (4H, s), 3.578-3.624 (3H, m), 4.479-4.519 (1H, t), 6.604-6.768 (3H, m); Mass (m/z): 432 Compound No. 54: l-{3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-l-yl]-propyl}-3,4-dimetyl-pyrrolidine-2,5-dione hydrochloride salt. IR (KBr): 1700.3 cm'1; 'HNMR (300 MHz, CDC13)8: 1.355-1.379 (3H, d), 1.669-1.913 (11H, m), 2.266 (2H, s), 2.961-3.061 (6H, m), 3.516-3.654 (8H, m), 4.746 (1H, s), 6.613-6.789 (3H, m); Mass (m/z): 432 (M++l). Compound No. 84: l-(3-{4-[2-(2,2,2-Trifluoro-ethoxy)-phenyl]-piperazin-l-yl}-propyl)- 3,4-dimethyl- pyrrolidine-2,5-dione hydrochloride salt. IR (KBr): 1704 cm'1; Mass (m/z): 428 (M++l). Compound No. 88: l-{3-[4-(2-Cyclopentyloxy-phenyl)-piperazm-l-yl]-propyl}-3,4-dimethyl-pyrrolidine-2,5-dione hydrochloride salt. IR (KBr): 1697 cm"1; Mass (m/z): 413 (M++l). Compound No. 96: l-{3-[4-(5-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3,4-dimethyl-pyrrolidine-2,5-dione hydrochloride salt. 'HNMR (300 MHz, CDC13)8: 1.224-1.246 (6H, d), 2.230-2.282 (2H, t), 3.031-3.048 (6H, d), 3.498-3.648 (8H, m), 3.837 (3H, s), 6.659-6.781 (3H, m); Mass (m/z): 378 (M++l). Compound No. 100: l-{3-[4-(3-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3,4-dimethyl-pyrrolidine-2,5-dione hydrochloride salt. IR (KBr): 1693.0 cm"1; 'HNMR (300 MHz, CDC13)5: 1.227-1.246 (6H, d), 2.239-2.288 (2H, t), 3.039-3.115 (6H, m), 3.555-3.651 (8H, m), 3.911 (3H, s), 6.685-6.993 (3H, m); Mass (m/z): 378 Compound No. 106: l-{3-[4-(3-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3,4-dimethyl-pyrrolidine-2,5-dione hydrochloride salt. 'HNMR (300 MHz, CDC13)8: 1.24-1.35 (12H, t), 2.27 (2H, s), 3.05-3.21 (6H, t), 3.44-3.64 (8H, m), 4.61 (1H, s), 6.86-6.96 (3H, m); Mass (m/z): 406 (M++l). Compound No. 1 22 : 1 - { 3 - [4-(5-Fluoro-2-propoxy-phenyl)-piperazin- 1 -yl] -propyl } -3 -methyl-pyrrolidine-2,5-dione hydrochloride salt. 'H NMR (300 MHz, CDC13)8: 1.016-1.065 (3H,t), 1.569(3H,s), 1.790-1.859 (2H, q), 2.142 (2H, s), 2.439 (3H, s), 2.605-2.667 (2H, d), 2.984-3.048 (4H, d), 3.363 (4H, s), 3.649-3.667 (2H, t), 3.888-3.931 (2H, t), 6.606-6.752 (3H, m); Mass (m/z): 421 (M++l). Compound No. 1 34 : 1 - { 3-[4-(3-Fluoro-2-methoxy-phenyl)-piperazin- 1 -yl] -propyl } -3-methyl-pyrrolidine-2,5-dione hydrochloride salt. IR (KBr): 1702.9 cm"1; 'HNMR (300 MHz, CDC13)8: 1.356-1.379 (3H, t), 2.258-2.392 (3H, m), 2.414-3.078 (6H, m), 3.479-3.658 (8H, m), 3.912 (3H, s), 6.680-6.994 (3H, m); Mass (m/z): 364 Compound No . 1 44 : 1 - { 3 - [4-(2-Cyclopropylmethoxy-phenyl)-piperazin- 1 -yl] -propyl } -3-methyl-pyrrolidine-2,5-dione hydrochloride salt. 'HNMR (CDC13 300 MHz)8: 0.33-0.34 (2H, d), 0.61-0.62 (2H, d), 0.65 (1H, s), 1.35-1.37 (3H, d), 2.21-2.38 (3H, m), 2.94-3.03 (6H, m), 3.47-3.51 (6H, d), 3.60-3.65 (2H, t), 3.83-3.86 (2H, d), 6.80-7.00 (4H, m). Compound No. 170: 1 - {3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-1 -yl]-propyl}-3-methyl-pyrrolidine-2,5-dione hydrochloride salt. Compound No. 188: l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrolidine-2,5-dione hydrochloride salt. IR: 1699.6 cm'1; 'HNMR (300 MHz, CDC13)8: 1.32-1.34 (6H, d), 2.26-2.39 (3H, t), 2.96-3.12 (6H, t), 3.53-3.63 (8H, d), 4.47-4.51 (1H, t), 6.63-6.80 (3H, m); Mass (m/z): 392 (M++l). Compound No. 192: 1 -{3-[4-(5-Fluoro-2-methoxy-phenyl)-piperazin-1 -yl]-propyl}-3-methyl-pyrrolidine-2,5-dione hydrochloride salt. IR: 1694.7 cm'1; 'HNMR (300 MHz, CDC13)8: 1.354-1.377 (3H, d), 2.235-2.388 (3H, m), 2.944-3.083 (6H, m), 3.502-3.654 (8H, m), 3.837 (3H, s), 6.650-6.810 (3H, m); Mass (m/z): 364.3 (M++l). Compound No. 194: 1 -{3-[4-(2-Cyclopentyloxy-phenyl)-piperazin-1 -yl]-propyl}-3-methyl-pyrrolidine-2,5-dione hydrochloride salt. IR: 1694.2 cm'1; 'HNMR (300 MHz, CDC13)6: 1.358-1.379 (3H, d), 1.489 (2H, s), 1.668-1.688 (2H, d), 1.880-2.053 (4H, m), 2.249-2.392 (3H, t), 2.962-3.035 (2H, t), 3.146 (2H, s), 3.574-3.652 (6H, t), 3.947-3.991 (2H, d), 4.316 (2H, s), 4.881 (1H, s), 6.939-7.296 (4H, m); Mass . (m/z):400(M++l). Compound No. 198: l-{3-[4-(3-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrolidine-2,5-dione hydrochloride salt. 'HNMR (300 MHz, CDC13)5: 1.18-1.30 (6H, m), 1.35-1.37 (3H, d), 2.18-2.23 (2H, t), 2.34-2.38 (1H, d), 2.90-3.03 (5H, m), 3.19 (2H, s), 3.45-3.51 (5H, t), 3.61-3.65 (2H, t), 4.48-4.52 (1H, m), 6.67-6.98 (3H, m). Example 6: Preparation of 2-{3-[4-(2-Cvclopentvloxv-5-fluoro-phenvl)-piperazin-l-vl]-propvl}-5,6-difluoro-hexahydro-isoindole-1.3-dione hydrochloride salt (Compound No. 8) Step 1: Preparation of 4-(3-bromopropyl) tetrahydro-la//-oxireno[/]isoindole-3,5(2//,4/f)-dione To a solution of 2-(3-bromopropyl)-3a, 4,7,7a-tetrahydroisoindole-l, 3-dione (1.0 gm, 0.0037 mole) in dichloromethane (lOmL) was added equimolar quantity of w-chloroperbenzoic acid (1.33 gm of 50%, 0.0037 mole) in dichloromethane at 0-5°C. The reaction mixture was stirred for about 6-8 hours. Reaction mixture was poured into ice cold potassium carbonate solution (5%) and concentrated to yield of the desired product. Yield: 0.8 gm (75%) Step 2: Preparation of 4-{3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-l-yl]-propyl}-hexahydro-l-oxa-4-aza-cyclopropa[f]indene-3,5-dione A suspension of 4-(3-bromopropyl) hexahydro-l-oxa-4-aza-cyclopropa[f] indene-3,5-dione (O.Sgm, 0.0028 mol), l-(5-Fluoro-2-cyclopentyloxyphenyl) piperazine (0.7 gm, 0.0028 mol), anhydrous potassium carbonate (0.46 gm, 0.003 mol) and potassium iodide (0.009 gm, 0.00005 mol) in dimethylformamide (20 ml) was heated at 50-55 °C for about 24 hours. Reaction was quenched by adding water (60 ml) to it; extracted with ethyl acetate, the combined organic layer was then dried over anhydrous sodium sulfate and concentrated to yield the crude product. It was then purified on a column of silica gel (60-120 mesh) using dichloromethane and methanol mixture as eluent. Yield: 0.6 gm, (62%). Step 3: Preparation of 2-{3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazm-l-yl]-propyl}-5, 6-difluoro-hexahydro-isoindole-1, 3-dione To the solution of 4-{3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-l-yl]-propyl}-hexahydro-l-oxa-4-aza-cyclopropa[f]indene-3, 5-dione (0.5 gm, 0.001 mol) in dichloromethane (15 ml) was added diethylaminosulfurtrifluoride (0.26 gm, 0.0016 mol) dropwise under stirring at 0-5 °C. The reaction mixture was allowed to come at room temperature and stirred for about 2-3 hours. After the completion of the reaction, it was quenched by adding dilute solution of sodium bicarbonate; extracted with dichloromethane and combined organic layers were concentrated to yield the crude product. It was then purified on a column of silica gel (60-120 mesh) using dichloromethane and methanol mixture as eluent to yield the desired product. Yield: 0.080 gm, (15%). Step 4: Preparation of 2-{3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-l-yl]-propyl}-5, 6-difluoro-hexahydro-isoindole-1, 3-dione hydrochloride salt An equimolar quantity of isopropyl alcohol-hydrochloric acid was added to 2- {3 - [4-(2-Cyclopentyloxy- 5 -fluoro-phenyl)-piperazin-1 -yl] -propyl} -5, 6-difluoro-hexahydro-isoindole-1, 3-dione and the resulting salt was solidified by adding ether to it. IR: 1704.6 cm'1; Mass (m/z): 494 (M++l); M.P: 189-195°C. The following compounds are prepared similarly Compound No. 120: 2-{3-[4-(2-Isopropoxy-phenyl)-piperazine-l-yl]-propyl}-5-chldro-6-fluoro-hexahydro-isoindole-1,3-dione hydrochloride salt. IR: 1701.5 cm'1; !HNMR (300 MHz, DMSO-d6)8: 1.27-1.29 (6H, d), 1.97-2.34 (6H, m), 2.98-3.24 (10H, m), 4.47 (1H, m), 4.56-4.66 (1H, m), 4.82-4.98 (1H, m), 6.88-6.96 (4H, m), 10.53 (1H, brs); Mass (m/z): 466.3 (M++l). Example 7: Preparation of l-l3-[4-(5-Fluoro-2-isopropoxv-phenyl)-piperazin-l-vl]-propvU-3-cvclopropvlamino-methyl-pvrrolidine-2.5-dione hydrochloride salt (Compound No. 160) Step 1: Preparation of l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-methylene-pyrrolidine-2,5-dione A solution of 3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propylamine (1.0 gm, 0.0034 mol) and itaconic anhydride (0.38 gm, 0.0034 mol) in toluene (15 ml) was refluxed for about 1 hour. After completion of the reaction the reaction mixture was concentrated to form a crude residue, which was then purified by column chromatography. Yield: 0.7 gm, (54%) Step 2: Preparation of l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylamino-methyl-pyrrolidine-2,5-dione To a solution of l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-methylene-pyrrolidine-2,5-dione (0.5 gm, 0.0013 mol) in methanol was added equimolar quantity of cyclopropylamine (0.073 gm, 0.0013 mol) and reaction mixture was stirred at room temperature for about 10-12 hours. The reaction mixture was concentrated to yield the crude product which was then purified on a column of silica gel (60-120 mesh) using dichloromethane and methanol mixture as eluent to yield the desired product. Yield: 0.3 gm, (53%). Step 3: Preparation,of l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylamino-methyl-pyrrolidine-2,5-dionehydrochloridesalt An equimolar quantity of isopropyl alcohol-hydrochloric acid was added to 1 - { 3-[4-(5 -Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -cyclopropylamino-methyl-pyrrolidine-2,5-dione and the resulting salt was solidified by adding ether to it IR (KBr): 1698.8 cm'1; 'HNMR (CDC13> 300 MHz)5: 0.74 (2H, s), 0.92 (2H, s), 1.20-1.23 (IH, m), 1.29-1.31 (6H, d), 1.65 (3H, s), 2.33-2.40 (3H, d), 2.69-2.75 (IH, d), 3.15 (2H, s), 3.45-3.51 (12H, m), 4.44-4.48 (IH, t), 6.61-6.79 (3H, m); Mass (m/z): 447 (M++l). The following compounds are prepared similarly Compound No. 124: l-{3-[4-(5-Fluoro-2-propoxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylamino-methyl-pyrrolidine-2,5-dionehydrochloride salt. IR (KBr): 1605 cm'1; Mass (m/z): 447 (M++l). Compound No. 126: l-{3-[4-(2-methoxy-5-methyl -phenyl)-piperazin- 1-yl]-propyl}-3-cyclopropylaminomethyl-pyrrolidine-2,5-dionehydrochloride salt. IR (KBr): 1704.4 cm'1; Mass (m/z): 415 (M++l). Compound No. 128: l-(3-{4-[5-Fluoro-2-(2,2,2-trifluoro-ethoxy)-phenyl]-piperazin-l-yl}-propyl)- 3-cyclopropylaminomethyl-pyrrolidine-2,5-dione hydrochloride salt. IR (KBr): 1716.8 cm'1; Mass (m/z): 487 (M++l). Compound No. 130: l-(3-{4-[2-(2,2,3,3-Tetrafluoro-propoxy)~phenyl]-piperazin-l-yl}-propyl)-3-cyclopropylaminomethyl-pyrrolidine-2,5-dione hydrochloride salt. IR (KBr): 1702.1 cm'1; Mass (m/z): 501 (M++l). Compound No. 132: l-(3-{4-[2-(2,2,3,3-Tetrafluoro-propoxy)-phenyl]-piperazin-l-yl}-propyl)-3-cyclobutylaminomethyl-pyrrolidine-2,5-dione hydrochloride salt. IR (DCM): 1709.2 cm"1; Mass (m/z): 515 (M++l). Compound No. 138: l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-methylaminomethyl-pyrrolidine-2,5-dione hydrochloride salt. IR (KBr): 1693 cm'1; Mass (m/z): 421 (M++l). Compound No. 140: l-{3-[4-(2-Cyclopropylmethoxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylamino-methyl-pyrrolidine-2,5-dione hydrochloride salt. IR (KBr): 1702.6 cm'1; 'HNMR (300 MHz, CDC13)5: 0.317-0.332 (2H, d), 0.610-0.636 (4H, d), 0.846-0.883 (2H, s), 1.256 (2H, s), 2.328 (4H, s), 2.692-2.752 (2H, d), 3.126-3.723 (14H, m), 3.822-3.845 (2H, d), 6.803-7.017 (4H, m); Mass (m/z): 441 (M++l). Compound No. 142: l-{3-[4-(2-Cyclopropylmethoxy-phenyl)-piperazin-l-yl]-propyl}-3-methylamino-methyl-pyrrolidine-2,5-dione hydrochloride salt. 'HNMR (300 MHz, DMSO)6: 0.33-0.34 (2H, d), 0.55-0.58 (3H, d), 1.24-1.26 (3H, d), 2.07 (2H, s), 2.61 (3H, s), 2.84-2.90 (3H, d), 2.99 (3H, s), 3.50-3.55 (9H, t), 3.83-3.86 (2H, d), 6.88-6.97 (4H, m). Compound No. 146: l-{3-[4-(2-Methoxy-phenyl)-piperazin-l-yl]-propyl}-3-methylaminomethyl-pyrrolidine-2,5-dione hydrochloride salt. 'HNMR (300 MHz, CDC13)6: 1.841 (3H, s), 2.008 (1H, s), 2.296 (3H, s), 2.464-2.579 (3H, t), 2.669-2.824 (6H, m), 3.111 (4H, s), 3.582-3.627 (2H, t), 3.858 (3H, s), 6.844-6.999 (4H, m); Mass (m/z): 375 (M++l). Compound No. 148: l-{3-[4-(2-Cyclopentyloxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylaminomethyl-pyrrolidine-2,5-dione hydrochloride salt. IR (KBr): 1715.3 cm'1; 'HNMR (300 MHz, CDC13)8: 0.81 (2H, s), 1.09 (1H, s), 1.20-1.25 (2H, t), 1.62-1.85 (10H, m), 2.34 (2H, s), 2.59 (1H, s), 2.75-2.80 (1H, d), 3.13 (2H, s), 3.39-3.75 (12H, m), 4.77 (1H, s), 6.82-6.98 (3H, m); Mass (m/z): 455 (MM). Compound No. 150: l-{3-[4-(2-Cyclopentyloxy-phenyl)-piperazin-l-yl]-propyl}-3-(isopropylamino-methyl)-pyrrolidine-2,5-dione hydrochloride salt. IR (KBr): 1705.9 cnV1; 'HNMR (300 MHz, CDC13)5: 1.50-1.84 (14H, m), 2.32-2.41 (3H, t), 2.72-2.81 (1H, d), 3.20-3.36 (4H, t), 3.44-3.55 (1H, q), 3.79-3.89 (6H, d), 4.75 (1H, s), 6.81-6.98 (3H, m); Mass (m/z): 457 (M++l). Compound No. 154: l-{3-[4-(3-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-(isopropylamino-methyl)-pyrrolidine-2,5-dione hydrochloride salt. IR (KBr): 1715.3 cm-'; 'HNMR (300 MHz, CDC13)8: 1 11-2.00 (15H, m), 2.48 (2H, s), 2.75 (1H, s), 3.35-3.93 (1H, m), 4.46 (1H, s), 6.64-6.91 (3H, m);Mass (m/z): 449 (M++l). Compound No. 156: l-{3-[4-(3-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylamino-methyl-pyrrolidine-2,5-dione hydrochloride salt. IR (KBr): 1709.2 cm'1; 'HNMR (300 MHz, CDC13)8: 0.86-0.88 (4H, d), 1.18-1.41 (6H, m), 1.77 (2H, s), 2.37 (2H, s), 2.58 (1H, s), 2.73-2.79 (1H, d), 3.16-4.07 (14H, m), 4.45 (1H, s), 6.65-6.97 (3H, m); Mass (m/z): 447 (M++l). Compound No. 162: l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-(isopropylamino-methyl)-pyrrolidine-2,5-dione hydrochloride salt. IR (KBr): 1698.7 cm'1; 'HNMR (300 MHz, CDC13)6: 1.199-1.693 (15H, m), 2.006 (2H, s), 2.452 (1H, s), 3.331-4.025 (14H, m), 4.440 (1H, s), 6.606-6.778 (3H, m); Mass (m/z): 449 Compound No. 164: l-{3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-l-yl]-propyl}-3-[(cyclopropylmethylamino)methyl]-pyrrolidine-2,5-dione hydrochloride salt. IR (KBr): 1712.5 cm'1; 'HNMR (300 MHz, CDC13)8: 1.25 (3H, s), 1.33-1.83 (13H, m), 2.42 (2H, s), 2.82 (2H, s), 3.17 (4H, s), 3.42-3.78 (10H, m), 4.73 (1H, s), 6.60-6.73 (3H, m); Mass (m/z): 487 (M++l). Compound No. 166: l-{3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-l-yl]-propyl}-3-isopropylamino-methyl)-pyrrolidine-2,5-dione hydrochloride salt. Compound No. 168: l-{3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylaminomethyl-pyrrolidine-2,5-dione hydrochloride salt. Compound No. 176: l-{3-[4-(4-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-[(cyclopropyl-methyl-amino)-methyl]-pyrrolidine-2,5-dione hydrochloride salt. IR: 1699.9 cm'1; Mass: 460 (M++l). Compound No. 178: l-{3-[4-(2-Methoxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropyl-methyl-amino-methyl]-pyrrolidine-2,5-dione hydrochloride salt. IR: 1716.5 cm'1; Mass: 414 (M++l). Compound No. 180: l-(3-{4-(2-(2,2,2-Trifluoro-ethoxy)-phenyl]-piperazin-l-yl}-propyl)- 3-cyclopropyl-methyl-amino-methyl] -pyrrolidine-2,5 -dione hydrochloride salt. IR: 1707.0 cm'1; Mass: 482 (M++l). Compound No. 182: l-{3-[4-(2-Methoxy-phenyl)-piperazin-l-yl]-propyl}-3-(isopropylamino)-methyl)-pyrrolidine-2,5-dione hydrochloride salt. IR: 1664.9 cm'1; Mass: 402 (M++l). Example 8: Preparation of 5-(3-[4-(5-Fluoro-2-isopropoxv-phenylVpiperazin-l-vl]-propvU-5-aza-spiro[2.4] heptane-4,6-dione hydrochloride salt (Compound No. 136) To a suspension of sodium hydride (0.037 gm, 0.0015 mol) in dimethylsulfoxide (15ml) was added trimethylsulphoxonium iodide (0.34 gm, 0.0015 mol) in lots at room temperature. It was followed by the addition of solution of l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-methylene-pyrrolidine-2,5-dione (0.5 gm, 0.0013 mol) in dimethylsulfoxide (5ml) to a clear reaction mixture at 10-15°C. Reaction mixture was stirred for about 10-15 minutes. Reaction was quenched by adding water (30 ml) to it. It was extracted with ethyl acetate; combined organic layers were concentrated to yield the crude product. It was then purified by column chromatography. Yield: 0.2 gm, (39%) IR (KBr): 1737 cm'1; Mass (m/z): 404 (M++l). The following compounds are prepared similarly Compound No. 152: 5-{3-[4-(2-Cyclopentyloxy-phenyl)-piperazin-l-yl]-propyl}-5-aza-spiro[2.4]heptane- 4,6-dione hydrochloride salt. 'HNMR (300 MHz, CDC13)8: 1.25 (2H, s), 1.39-1.44 (2H, m), 1.52 (2H, s), 1.65 (3H, s),-1.91-2.03 (4H, q), 2.16 (2H, s), 2.30-2.32 (1H, d), 3.11 (2H, s), 3.51-3.61 (6H, d), 4.28 (2H, s), 4.60 (2H, s), 4.91 (1H, s), 6.99-7.38 (3H, m); Mass (m/z): 412.5 (M++l). Compound No. 158: 5-{3-[4-(3-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-5-aza-spiro[2.4]heptane- 4,6-dione hydrochloride salt. 'HNMR (300 MHz, CDC13)8: 1.28-1.30 (6H,d), 1.37-1.51 (4H, m), 2.20-2.31 (4H,t), 2.93-3.02 (4H, d), 3.49-3.59 (8H, d), 4.44-4.50 (1H, m), 6.67-6.99 (3H, m); Mass (m/z): 404 (M++l). Compound No. 184: 5-(3-{4-[2-(2,2,2-Trifluoro-ethoxy)-phenyl]-piperazin-l-yl}-propyl)-5-aza-spiro[2.4]heptane-4,6-dione hydrochloride salt. IR: 1703.8 cm'1; Mass: 425 (M++l). Pharmacological testing Receptor Binding Assay Receptor binding assays were performed using native a-1 adrenoceptors. The affinity of different compounds for otia and aib adrenoceptor subtypes was evaluated by studying their ability to displace specific [3H] prazosin binding from the membranes of rat submaxillary and liver respectively (Michel et al, Br. J. Pharmacol, 98, 883-889 (1989)). The binding assays were performed according to U'Prichard et al. (Eur. J. Pharmacol, 50:87-89 (1978) with minor modifications. Submaxillary glands were isolated immediately after sacrifice. The liver was perfused with buffer (Tris HCI 50 mM, NaCl 100 mM, 10 mM EDTA pH 7.4). The tissues were homogenized in 10 volumes of buffer (Tris HCI 50 mM, NaCl 100 mM, EDTA 10 mM, pH 7.4). The homogenate was filtered through two layers of wet guaze and filtrate was centrifuged at 500g for 10 min. The supernatant was subsequently centrifuged at 40, OOOg for 45 min. The pellet thus obtained was re-suspended in the same volume of assay buffer (Tris HCI 50 mM, EDTA 5 mM, pH 7.4) and were stored at -70 °C until the time of assay. The membrane homogenates (150-250 ug protein) were incubated in 250 ^il of assay buffer (Tris HCI 50 mM, EDTA 5 mM, pH 7.4) at 24-25 °C for I hour. Non-specific binding was determined in the presence of 300 nM prazosin. The incubation was terminated by vacuum filtration over GF/B fiber filters. The filters were then washed with ice cold 50 mM Tris HCI buffer (pH 7.4). The filter mats were dried and bounded radioactivity retained on filters was counted. The ICso and Kd were estimated by using the non-linear curve-fitting program using G pad prism software. The value of inhibition constant Ki was calculated from competitive binding studies by using Cheng and Prusoff equation (Cheng and Prusoff, Biochem. Pharmacol., 1973, 22:3099-3 108), Kj = IC50 /(l+L/Kd) where L is the concentration of [3H] prazosin used in the particular experiment. The pKi values were in the range of about 6.80 to about 1 1 and about 5 to about 7.5 for aia and aib subtype adrenergic receptors, respectively. In vitro functional studies In vitro alpha- 1 Adrenoceptor selectivity In order to study selectivity of action of the present compounds towards different alpha- 1 adrenoceptor subtypes, the ability of these compounds to antagonize alpha- 1 adrenoceptor agonist induced contractile response of aorta (alpha- Id), prostate (alpha- la) and spleen (alpha- Ib) was studied. Aorta, prostate and spleen tissue were isolated from thipentane anaesthetized (« 300 nig/Kg) male wistar rats. Isolated tissues were mounted in organ bath containing Krebs Henseleit buffer of the following composition (mM): NaCl 118; KC14.7; CaCl2 2.5; MgS04. 7H20 1.2; NaHCOs 25; KH2PO4 1.2; glucose 11.1. Buffer was maintained at 37 °C and aerated with a mixture of 95% 02 and 5% CO2. A resting tension of 2 g (aorta and spleen) or 1 g (prostate) was applied to tissues. Contractile response was monitored using a force displacement transducer and recorded on chart recorders. Tissues were allowed to equilibrate for 1 and 1/2 hours. At the end of equilibration period, concentration response curves to norepinephrine (aorta) and phenylephirine (spleen and prostate) were obtained in the absence and presence of the tested compound (at concentration of 0.1, 1 and 10 uM). The pK-B values were in the range of 8 to 10, 6.80 to 9 and 7.5 to 9 for a.\a, a]b and a]d subtype adrenergic receptor, respectively. WE CLAIM: 1. A compound having the structure of Formula I, O Formula I (Figure Remove) pharmaceutically acceptable acid addition salts, solvates, enantiomers, diastereomers, regioisomers, N-oxides, polymorphs, prodrugs or metabolites thereof, wherein: Ri is alkyl, cycloalkyl or R3N(R4)(CH2)m; R2 is hydrogen, alkyl, cycloalkyl or R3N(R4)(CH2)m; m is an integer 0 or 1; R3 is alkyl or cycloalkyl; RI is hydrogen or alkyl; RI and R2 together form cycloalkyl or cycloalkenyl; R<0. Ris RS is alkyl or cycloalkyl; Rs is hydrogen, halogen or alkyl; is optional double bond; n is an integer of from 1 to 2. 2. A compound according to claim 1 wherein: Ri is alkyl, cycloalkyl or R3N(R4)(CH2)m; R2 is hydrogen, alkyl or R3N(R4)(CH2)m; m is an integer 0 or 1; R3 is cycloalkyl or .optionally substituted alkyl wherein optional substituents are alkynyl or cycloalkyl; Rt is hydrogen or alkyl; RI and R2 together form optionally substituted cycloalkyl or cycloalkenyl wherein optional substituents are halogen. Ris R5 is cycloalkyl or optionally substituted alkyl wherein optional substituents are halogen or cycloalkyl; Re is hydrogen, halogen or alkyl. 3. A compound, which is: 1 - {3 - [4-(5 -Fluoro-2-propoxy-phenyl)-piperazin-1 -yl] -propyl} -3-methyl-4-methylamino-pyrrolidine-2,5-dione and its hydrochloride salt, 2-(3-{4-[2-(2,2,3,3-Tetrafluoro-propoxy)-phenyl]-piperazin-l-yl}-propyl)-hexahydro-isoindole-l,3-dione and its hydrochloride salt, 1 - {3 - [4-(5 -Fluoro-2-propoxy-phenyl)7piperazin-1 -yl] -propyl} -3 -cyclopropylamino-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 2- {3 - [4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-1 -yl] -propyl} -5,6-difluoro-hexahydro-isoindole-l,3-dione and its hydrochloride salt, l-{3-[4-(2-Methoxy-5-methyl-phenyl)-piperazin-l-yl]-propyl}-3,4-dimethyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 - [4-(2-Methoxy-5 -methyl-phenyl)-piperazin-1 -yl] -propyl} -3 -methyl-4-methylamino-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 - [4-(2-Methoxy-5 -methyl-phenyl)-piperazin-1 -yl] -propyl} -3 -cyclopropylamino-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3- [4-(5 -Fluoro-2-propoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -cy clobutylamino-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, l.(3-{4-[5-Fluoro-2-(2,2,2-trifluoro-ethoxy)-phenyl]-piperazin-l-yl}-propyl)- 3-cyclopropylamino-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 -(3-{4-[5-Fluoro-2-(2,2,2-trifluoro-ethoxy)-phenyl]-piperazin-1 -yl}-propyl)-3-methyl-4-methylamino-pyrrolidine-2,5-dione and its hydrochloride salt, l-(3-{4-[5-Fluoro-2-(2,2,2-trifluoro-ethoxy)-phenyl]-piperazin-l-yl}-propyl)-3,4-dimethyl-pyrrolidine-2,5-dione and its hydrochloride salt, l-(3-{4-[2-(2,2,3,3-Tetrafluoro-propoxy)-phenyl]-piperazin-l-yl}-propyl)-3,4-dimethyl-pyrrolidine-2,5-dione and its hydrochloride salt, l-(3-{4-[2-(2,2,3,3-Tetrafluoro-propoxy)-phenyl]-piperazin-l-yl}-propyl)- 3-cyclopropylamino-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 -(3- {4-[2-(2,2,3,3-Tetrafluoro-propoxy)-phenyl]-piperazin-1 -yl} -propyl)- 3-cyclobutylamino-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3-[4-(2-Cyclopentyloxy-phenyl)-piperazin-1 -yl]-propyl} -3-cyclobutylamino-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 2-{3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-l-yl]-propyl}-hexahydro-isoindole-l,3-dione and its hydrochloride salt, 1 - {3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -methyl-4-methyl amino-pyrrolidine-2,5-dione and its hydrochloride salt, l-{3-[4-(5-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-4-methylamino-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3- [4-(2-Cyclopropylmethoxy-phenyl)-piperazin-1 -yl] -propyl} -3,4-dimethyl-pyrrolidine-2,5-dione and its hydrochloride salt, 2-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-hexahydro-isoindole-1,3-dione and its hydrochloride salt, 2-{3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-l-yl]-propyl}-3a,4,7,7a-tetrahydro-isoindole-l,3-dione and its hydrochloride salt, 1 - {3 - [4-(2-Cyclopropylmethoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -cyclopropylamino-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 2-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3a,4,7,7a-tetrahydro-isoindole-l,3-dione and its hydrochloride salt, 1. {3- [4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -cyclobutylamino-4-methyl-pyrrolidin-2,5-dione and its hydrochloride salt, 1. {3 -[4-(3 -Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -methyl-4-methylamino-pyrrolidine-2,5-dione and its hydrochloride salt, 1. {3 -[4-(2-Cyclopropylmethoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -isopropylamino-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1. {3 -[4-(2-Cyclopentyloxy-5 -fluoro-phenyl)-piperazin-1 -yl] -propyl} -3,4-dimethyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1. {3 - [4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-1 -yl] -propyl} -3 -cyclopropylamino-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1. {3 - [4-(5 -Fluoro-2-methoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -(cyclopropylmethyl-amino)-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 - [4-(5 -Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -(cyclopropylmethyl-amino)-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, l-{3-[4-(5-Fluoro-2-trifluoromethoxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylamino-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1. { 3 - [4-(2-Methoxy-phenyl)-piperazin-1 -yl] -propyl} -3-(cyclopropylmethyl-amino)-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 - [4-(2-Isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -isopropylamino-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, l-{3-[4-(2-Isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylamino-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, l-{3-[4-(2-Methoxy-phenyl)-piperazin-l-yl]-propyl}-3-isopropylamino-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 - [4-(5 -Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3,4-dimethy 1-pyrrole-2,5-dione and its hydrochloride salt, 1 - {3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3,4-dimethyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 - [4-(5 -Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -cyclopropylamino-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 - [4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -isopropylamino-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 - [4-(5 -Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -(cyclopropyl-methyl-amino)-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, l-(3-{4-[2-(2,2,2-Trifluoro-ethoxy)-phenyl]-piperazin-l-yl}-propyl)-3,4-dimethyl-pyrrole-2,5-dione and its hydrochloride salt, l-(3-{4-[2-(2,2,2-Trifluoro-ethoxy)-phenyl]-piperazin-l-yl}-propyl)-3,4-dimethyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1. {3-[4-(2-Cyclopentyloxy-phenyl)-piperazin-1 -yl] -propyl} -3,4-dimethyl-pyrrole-2,5-dione and its hydrochloride salt, 1 - {3- [4-(2-Cyclopentyloxy-phenyl)-piperazin-1 -yl] -propyl} -3,4-dimethyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 - [4-(2-Cyclopentyloxy-phenyl)-piperazin-1 -yl] -propyl} -3 -isopropylamino-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 - [4-(5-Fluoro-2-methoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -cyclopropylamino-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1. {3 - [4-(2-Cyclopentyloxy-phenyl)-piperazin-1 -yl] -propyl} -3-methyl-4-methylamino-pyrrolidine-2,5-dione and its hydrochloride salt, l-{3-[4-(5-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3,4-dimethyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 - [4-(3 -Fluoro-2-methoxy-phenyl)-piperazin-1 -yl] -propyl} -3,4-dimethyl-pyrrole-2,5 -dione and its hydrochloride salt, 1 - {3 -[4-(3 -Fluoro-2-methoxy-phenyl)-piperazin-1 -yl] -propyl} -3,4-dimethyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 - [4-(3 -Fluoro-2-methoxy-phenyl)-piperazin-1 -yl] -propyl} -3-methyl-4-methylamino-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3- [4-(3-Fluoro-2-methoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -cyclopropylamino-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3- [4-(3-Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3,4-dimethyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 - [4-(3 -Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -cyclopropylamino-4-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 2-(3-{4-[2-(2,2,3,3-Tetrafluoro-propoxy)-phenyl]-piperazin-l-yl}-propyl)-3a,4,7,7a-tetrahydro-isoindole-l,3-dione and its hydrochloride salt, 2-{4-[4-[2-Isopropoxy-phenyl]-piperazin-l-yl]-butyl}-3a,4,7,7a-tetrahydro-isoindole-1,3-dione and its hydrochloride salt, 2- {3 - [4-(4-Fluoro-2-methoxy-phenyl)-piperazin-1 -yl] -propyl} -3 a,4,7,7a-tetrahydro-isoindole-l,3-dione and its hydrochloride salt, 2-(3 - {4- [4-Fluoro-2-(2,2,2-trifluoro-ethoxy)-phenyl] -piperazin-1 -yl} -propyl)-3 a,4,7,7a-tetrahydro-isoindole-1,3-dione and its hydrochloride salt, 2-{3-[4-(4-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3a,4,7,7a-tetrahydro-isoindole-l,3-dione and its hydrochloride salt, 2-{3-[4-(2-Isopropoxy-phenyl)-piperazin-l-yl]-propyl}-5-chloro-6-fluoro-hexahydro-isoindole-1,3-dione and its hydrochloride salt, 1 - {3 - [4-(5 -Fluoro-2-propoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1. {3- [4-(5 -Fluoro-2-propoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -cyclopropylamino-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1. { 3. [4-(2-methoxy-5 -methyl-phenyl)-piperazin-1 -yl] -propyl} -3 -cyclopropylamino methyl-pyrrolidine-2,5-dione and its hydrochloride salt, l-(3-{4-[5-Fluoro-2-(2,2,2-trifluoro-ethoxy)-phenyl]-piperazin-l-yl}-propyl)-3-cyclopropylaminomethyl-pyrrolidine-2,5-dione and its hydrochloride salt, l-(3-{4-[2-(2,2,3,3-Tetrafluoro-propoxy)-phenyl]-piperazin-l-yl}-propyl)-3-cyclopropylaminomethyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 -(3-{4-[2-(2,2,3,3-Tetrafluoro-propoxy)-phenyl]-piperazin-1 -yl}-propyl)- 3-cyclobutylamino-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, l-{3-[4-(3-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 5 - {3 - [4-(5 -Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -5 -aza-spiro [2.4] heptane-4,6-dione and its hydrochloride salt, 1 - {3- [4-(5 -Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -methylaminomethyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3- [4-(2-Cyclopropylmethoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -cyclopropylamino-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, l-{3-[4-(2-Cyclopropylmethoxy-phenyl)-piperazin-l-yl]-propyl}-3-methylamino-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 - [4-(2-Cyclopropylmethoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 - [4-(2-Methoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -methylaminomethyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 - [4-(2-Cyclopentyloxy-phenyl)-piperazin-1 -yl] -propyl} -3-cyclopropylaminomethyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 - [4-(2-Cyclopentyloxy-phenyl)-piperazin-1 -yl] -propyl} -3 -(isopropylamino-methyl)-pyrrolidine-2,5-dione and its hydrochloride salt, 5-{3-[4-(2-Cyclopentyloxy-phenyl)-piperazin-l-yl]-propyl}-5-aza-spiro[2.4]heptane-4,6-dione and its hydrochloride salt, 1 - {3- [4-(3 -Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -(isopropylamino-methyl)-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3- [4-(3-Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -cyclopropylamino-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 5-{3-[4-(3-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-5-aza-spiro[2.4]heptane-4,6-dione and its hydrochloride salt, 1 - {3 - [4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -cyclopropylamino-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1. {3 - [4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -(isopropylamino-methyl)-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 -[4-(2-Cyclopentyloxy-5 -fluoro-phenyl)-piperazin-1 -yl] -propyl} -3 - [(cyclopropyl-methyl-amino)-methyl]-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 -[4-(2-Cyclopentyloxy-5 -fluoro-phenyl)-piperazin-1 -yl] -propyl} -3 -isopropylamino-methyl)-pyrrolidine-2,5-dione and its hydrochloride salt, l-{3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-l-yl]-propyl}-3-cyclopropylaminomethyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3- [4-(2-Cyclopentyloxy-5 -fluoro-phenyl)-piperazin-1 -yl] -propyl} -3 -methyl-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3-[4-(2-Cyclopentyloxy-5-fluoro-phenyl)-piperazin-1 -yl]-propyl} -3-methyl-pyrrole-2,5-dione and its hydrochloride salt, 1 - {3 - [4-(2-Methoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -methyl-4-prop-2-ynylamino-pyrrolidine-2,5-dione (Compound No. 173) and its hydrochloride salt, 1 - {3 - [4-(4-Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -[(cyclopropyl-methyl-amino)-methyl]-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 - [4-(2-Methoxy-phenyl)-piperazin-1 -yl] -propyl} -3 - [(cyclopropyl-methyl-amino)-methyl]-pyrrolidine-2,5-dione and its hydrochloride salt, l-(3-{4-(2-(2,2,2-Trifluoro-ethoxy)-phenyl]-piperazin-l-yl}-propyl)- 3-[(cyclopropyl-methyl-amino)-methyl]-pyrrolidine-2,5-dione and its hydrochloride salt, 1 - {3 - [4-(2-Methoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -(isopropylamino)-methyl)-pyrrolidine-2,5-dione and its hydrochloride salt, 5 -(3- {4- [2-(2,2,2-Trifluoro-ethoxy)-phenyl] -piperazin-1 -yl} -propyl)-5 -aza-spiro[2.4]heptane-4,6-dione and its hydrochloride salt, 1 - { 3 - [4-(5 -Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -methyl-pyrrole-2,5 -dione and its hydrochloride salt, l-{3-[4-(5-Fluoro-2-isopropoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, l-{3-[4-(5-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrole-2,5-dione and its hydrochloride salt, l-{3-[4-(5-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, l-{3-[4-(2-Cyclopentyloxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrolidine-2,5-dione and its hydrochloride salt, l-{3-[4-(3-Fluoro-2-methoxy-phenyl)-piperazin-l-yl]-propyl}-3-methyl-pyrrole-2,5-dione and its hydrochloride salt, 1. {3- [4-(3-Fluoro-2-isopropoxy-phenyl)-piperazin-1 -yl] -propyl} -3 -methyl-pyrrolidine-2,5-dione and its hydrochloride salt, pharmaceutically acceptable acid addition salts, solvates, enantiomers, diastereomers, regioisomers, N-oxides, polymorphs, prodrugs or metabolites thereof. 4. A pharmaceutical composition comprising a therapeutically effective amount of a compound of claim 1 optionally together with pharmaceutically acceptable carriers, excipients or diluents. Use of a compound having the structure of Formula I, O N—R 5. 6. 7. 8. 9. 10. 11. 12. (Figure Remove) Formula I pharmaceutically acceptable acid addition salts, solvates, enantiomers, diastereomers, regioisomers, N-oxides, polymorphs, prodrugs or metabolites thereof, wherein RI, R2, R and n are the same as defined in claim 1, in the manufacture of a medicament for treating a disease or disorder mediated through aia and/ or a^ adrenergic receptors. Use of a pharmaceutical composition of claim 4 for treating a disease or disorder " mediated through aia and/ or aid adrenergic receptors. The use according to claim 5 or 6 wherein a disease or disorder is benign prostatic hyperplasia. Use of a compound having the structure of Formula I, N—R (Figure Remove) Formula I pharmaceutically acceptable acid addition salts, solvates, enantiomers, diastereomers, regioisomers, N-oxides, polymorphs, prodrugs or metabolites thereof, wherein RI, R2, R and n are the same as defined in claim 1, in the manufacture of a medicament for treating lower urinary tract symptoms associated with or without benign prostatic hyperplasia. The use according to claim 8 wherein lower urinary tract symptoms are irritative symptoms or obstructive symptoms. The use according to claim 9 wherein irritative symptoms are selected from frequent urination, urgent urination, nocturia and unstable bladder contractions and obstructive symptoms are hesitancy, poor stream, prolong urination and feelings of incomplete emptying. The use according to claim 8 wherein the said patient is a male or female. A process for preparing a compound of Formula VI, N—R (Figure Remove) Formula VI pharmaceutically acceptable acid addition salts, solvates, enantiomers, diastereomers, regioisomers, N-oxides, polymorphs, prodrugs or metabolites thereof, wherein: , RI, RI and R are same as defined in claim 1, which method comprises the steps of: (a) reacting a compound of Formula II with acrylonitrile H—N N—R Formula II to form a compound of Formula III; (Figure Remove) Formula III (b) hydrogenating the compound of Formula III to form a compound of Formula IV; N—R (Figure Remove) Formula IV (c) treating the compound of Formula IVwith a compound of Formula V (Figure Remove) Formula V to form a compound of Formula VI. 13. A process for preparing a compound of Formula X, (Figure Remove) —R pharmaceutically acceptable acid addition salts, solvates, enantiomers, diastereomers, regioisomers, N-oxides, polymorphs, prodrugs or metabolites thereof, wherein: RI, RS, RI and R are same as defined in claim 1 , which method comprises the steps: (a) reacting a compound of Formula IV (Figure Remove) Formula IV with a compound of Formula VII (Figure Remove) o Formula VII to form a compound of Formula VIII; (Figure Remove) —R O Formula VIII (b) treating the comound of Formula VIII with a compound of Formula IX Formula IX to form a compound of Formula X. 14. A process for preparing a compound of Formula XI, (Figure Remove) —R O Formula XI pharmaceutically acceptable acid addition salts, solvates, enantiomers, diastereomers, regioisomers, N-oxides, polymorphs, prodrugs or metabolites thereof, wherein: RI and R are same as defined in claim 1, which method comprises: reducing a compound of Formula VIII (Figure Remove) — R O Formula VlTl to form a compound of Formula XI. 15. A process for preparing a compound of Formula XIII, (Figure Remove) O Formula XIII pharmaceutically acceptable acid addition salts, solvates, enantiomers, diastereomers, regioisomers, N-oxides, polymorphs, prodrugs or metabolites thereof, wherein: R is same as defined in claim 1, which method comprises the steps of: (a) reacting a compound of Formula IV with itaconic anhydride, N—R (Figure Remove) Formula IV to form a compound of Formula XII —R (Figure Remove) O Formula XII (b) treating the compound of Formula XII with a methylene transfer reagent to form • a compound of Formula XIII. 16. A process for preparing a compound of Formula XIV, N—R (Figure Remove) Formula XIV pharmaceutically acceptable acid addition salts, solvates, enantiomers, diastereomers, regioisomers, N-oxides, polymorphs, prodrugs or metabolites thereof, wherein: RS, R4 and R are same as defined in claim 1, which method comprises: treating a compound of Formula XII 17. (Figure Remove) 0 Formula XII with a compound of Formula IX R3R4NH Formula IX to form a compound of Formula XIV. A process for preparing a compound of Formula XVII, N—R N—R (Figure Remove) Formula XVII pharmaceutically acceptable acid addition salts, solvates, enantiomers, diastereomers, regioisomers, N-oxides, polymorphs, prodrugs or metabolites thereof, wherein: R and n are same as defined in claim 1, which method comprises the steps of: (a) reacting 3a,4,7,7a-tetrahydro-isoindole-l,3-dione with a compound of Formula XV (wherein X is a halogen) Formula XV to form a compound of Formula XVI O (Figure Remove) Formula XVI (b) treating the compound of Formula XVI with a compound of Formula II H—N N—R Formul? to form a compound of Formula XVII. 18. A process for preparing a compound of Formula XVIII, N—R (Figure Remove) Formula XVIII pharmaceutically acceptable acid addition salts, solvates, enantiomers, diastereomers, regioisomers, N-oxides, polymorphs, prodrugs or metabolites thereof, wherein: R and n are same as defined in claim 1, which method comprises: hydrogenating a compound of Formula XVII N—R Formula XVII (Figure Remove) 19. to form a compound of Formula XVIII. A process for preparing a compound of Formula XXII, N—R (Figure Remove) Formula XXII pharmaceutically acceptable acid addition salts, solvates, enantiomers, diastereomers, regioisomers, N-oxides, polymorphs, prodrugs or metabolites thereof, wherein: R and n are same as defined in claim 1, which method comprises the steps of: (a) reacting a compound of Formula XVI with a peroxyacid, Formula XVI (Figure Remove) to form a compound of Formula XIX; O (Figure Remove) 0 Formula XIX (b) treating the compound of Formula XIX with a compound of Formula II H—N N—R (c) Formula II to form a compound of Formula XX; N N—R (Figure Remove) ° Formula XX treating the compound of Formula XX with hydrochloric acid to form a compound of Formula XXI; N—R Formula XXI (Figure Remove) (d) treating the compound of Formula XXI with a fluorinating agent to form a compound of Formula XXII. 20. A process for preparing a compound of Formula XXIII, N—R (Figure Remove) O Formula XXIII pharmaceutically acceptable acid addition salts, solvates, enantiomers, diastereomers, regioisomers, N-oxides, polymorphs, prodrugs or metabolites thereof, wherein: R and n are same as defined in claim 1, which method comprises: reacting a compound of Formula XX with a fluorinating agent N—R (Figure Remove) 0 0 Formula XX to form a compound of Formula XXIII.