DESC:FIELD OF THE INVENTION
The present invention relates to an improved process for preparation of a herbicide compound. More particularly, the present invention relates to an improved process for the preparation of Tembotrione of Formula (I) using m-xylene.
BACKGROUND OF THE INVENTION
The Bayer Corporation developed Tembotrione (I), a trione herbicide, in 2007 which is an inhibitor of p-hydroxyphenylpyruvate dioxygenase (HPPD). Numerous nations, including the United States, Mexico, Belgium, France, Germany, the Netherlands, Brazil, and Selveya, have gained registration. Tembotrione works by preventing the synthesis of p-hydroxyphenylpyruvate dioxygenase, which in turn affects the conversion of hydroxypyruvate into homogentisate, causes tyrosine accumulation, hinders the biosynthesis of plastoquinone and tocopherol, further influences the biosynthesis of carotenoid, and causes the weeds to fade and turn yellow in two weeks.
Tembotrione (I) suppresses broadleaf weeds including amaranth, pigweed, mustard, morning glory and others, as well as grassy weeds like crabgrass and setaria in corn fields. In maize fields, it works well against resistant and cancerous weeds. It has a broad spectrum, quick action, and excellent environmental compatibility. According to pertinent surveys and reports, it also seems to have a slight production-increasing effect. This triketone compound has flexible application period, can be compounded with various products, can effectively prevent and remove annual broadleaf weeds and some gramineous weeds, is safe to crops, is safe the environment and succeeding crops, is mainly used for corn, and can also be used for lawn, sugarcane, rice, onion, sorghum, other small crops and the like. It has a wide weeding spectrum and a long weeding suitability, mainly targets various broad-leaved weeds and gramineous weeds in middle and late stages after germination of a corn field, has excellent control effects on thistle, field bindweed, speedwell, pepper weed, weasel flower, cleavers and the like, has no phytotoxicity even after the reap of crops.
Various synthesis routes of Tembotrione (I) have been reported, for instance: patent application no. CN104292137A of Wuhan Institute of Technology, which discloses the synthesis of Tembotrione (I) by starting material of 2- chlorotoluene, however, the said process involves very expensive reagents, involves high production cost, which involves separate isolation and treatment of the intermediate state, resulting in a cumbersome process, having low rate of reaction and low yield of the final product.
Reference can also be made to patent application no. CN106008290A of Anhui Jukai agrochemical co ltd., which reports synthesis technology of Tembotrione (I), wherein, the preparation of Tembotrione (I) involves an expensive and large amount condensing agent, and ultimately high synthesis cost of the final product.
Further, the currently reported route for synthesizing Tembotrione (I) mainly uses 2-chlorotoluene as the starting material, involving esterification, bromination, alkylation followed by reaction with cyclohexane. However, the said method has various shortcomings including high waste generation, overall low yield of the final compound, use of highly polluting and dangerous raw materials, such as p-toluene sulfonate Acid and liquid bromine, etc., production of excessive impurities and by-products.
Therefore, there is a need to overcome the problems associated with the prior arts in respect of preparation of Tembotrione (I), and to develop a production and improved process, which involves readily available reagents, involves effective synthesis steps, having high reaction efficiency, eco-friendly and industrially advantageous on commercial scale and avoids the use of highly toxic and highly polluting raw materials, reagents.
The present invention provides an improved process for preparation of Tembotrione (I), which involves m-xylene as a starting material. m-xylene is widely applied to the production of fine chemical products and intermediates. However, its use as starting material for preparation of Tembotrione (I) resulting in improved, higher yield, along with high purity and stability of Tembotrione (I) has not been found so far.
Thus, the present invention aims to develop an improved process for the preparation of the herbicide compound i.e., Tembotrione (I) in view of the deficiencies of the methods reported in the prior arts, and to improve the process route which uses environmental and userfriendly chemicals, reagents instead of high-risk chemicals, reagents from the perspective of production safety. The use of environment and user-friendly chemicals, reagents instead of toxic chemicals, reagents simplify the process, increases the yield, reduces the synthesis cost, reduces the emissions of the wastes, and is suitable for industrial scale-up production on commercial level.

OBJECTIVES AND ADVANTAGES OF THE INVENTION
The main objective of the present invention is to provide a simple, economically advantageous, and cost-effective process for the preparation of Tembotrione of Formula (I), with high purity and yield on a commercial scale.
Another objective of the present invention is to provide an effective improved process for the preparation of Tembotrione of Formula (I), by m-xylene as starting material.
Another objective of the present invention is to provide a novel and effective improved process for preparation of Tembotrione of formula (I), with reduced or minimal waste generation.
Another objective of the present invention is to provide an improved process for the preparation of Tembotrione of formula (I), that involves less expensive and readily available reagents and solvents.
Another objective of the present invention is to provide an improved process for the preparation of Tembotrione of formula (I), with an improved reaction rate and minimized side reaction and/or formation of by-products.
Another objective of the present invention is to provide an improved process for the preparation of Tembotrione of formula (I), which is industrially and economically robust process with safe operations.
Another objective of the present invention is to provide an improved process for the preparation of Tembotrione of formula (I), which results in an improved yield and purity of the final product.
Another objective of the present invention is to provide an improved process for the preparation of Tembotrione of formula (I), wherein, less effluent is generated.
Another objective of this invention is to obtain a compound (2), i.e., 1,3-dichloro-2,4-dimethylbenzene, by halogenating a compound-(1), i.e., m-xylene in the presence of a halogenating agent.
A further objective of this invention is to obtain a compound-(3), i.e., 2-Bromomethyl-1,3-dichloro-4-methyl-benzene , by halogenating the compound-(2) i.e., 1,3-dichloro-2,4-dimethylbenzene, in the presence of a halogenating agent, a free radical initiator and a solvent.
A further objective of this invention is to obtain a compound-(4), i.e., 1,3-Dichloro-4-methyl-2-(2,2,2-trifluoro-ethoxymethyl)-benzene, by reacting the compound-(3) i.e., 2-Bromomethyl-1,3-dichloro-4-methyl-benzene, with 2,2,2-trifluoroethan-1-ol (Trifluoroethanol) in the presence of base.
A further objective of this invention is to obtain a compound-(5), i.e., 2-Chloro-1-methyl-4-methylsulfanyl-3-(2,2,2-trifluoro-ethoxymethyl)-benzene, by reacting the compound-(4) i.e., 1,3-Dichloro-4-methyl-2-(2,2,2-trifluoro-ethoxymethyl)-benzene, in the presence with sodium thiomethoxide or methyl thiol and a base.
A further objective of this invention is to obtain a compound-(6), i.e., 2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoro-ethoxymethyl)-benzoic acid, by oxidizing the compound-(5), i.e., 2-Chloro-1-methyl-4-methylsulfanyl-3-(2,2,2-trifluoro-ethoxymethyl)-benzene, in the presence of an oxidizing agent.
Some or all these and other objects of the invention can be achieved by way of the invention described hereinafter.
ADVANTAGES:
1. The improved process of the present invention involves readily available reagents, involves effective synthesis steps, having high reaction efficiency, eco-friendly and industrially advantageous on commercial scale and avoids the use of highly toxic and highly polluting raw materials, reagents.
2. The improved process of the present invention is cost effective and consistently reproducible process for the preparation of pure Tembotrione (I).
3. The improved present invention involves an improved process route which utilizes environmental and user-friendly chemicals, reagents instead of high-risk chemicals, reagents from the perspective of production safety. The use of environment and user-friendly chemicals, reagents instead of toxic chemicals, reagents simplify the process, increases the yield, reduces the synthesis cost, reduces the emissions of the wastes, and is suitable for industrial scale-up production on commercial level.
4. The improved process of the present invention is simple to handle and economically viable as there is a large amount of reduction in solvent volume.
5. The reaction time in an improved process of the present invention is reduced which in turn reduces the operational cost.
6. The improved process of the present invention is more environmentally friendly.
7. The improved process of the present invention provides final product in high yield and high purity.
8. The process of the present invention involves m-xylene as a starting material as m-xylene is available commercially at a viable cost.
9. The use of m-xylene as a starting material for preparation of Tembotrione (I) results in an improved production of final product with higher yield, along with high purity Tembotrione (I).

SUMMARY OF THE INVENTION
Accordingly, the main aspect of the present invention is to provide an improved process for the preparation of Tembotrione of Formula (I). Provided herein is simple, cost effective and consistently reproducible process for the preparation of highly pure and stable form of Tembotrione with higher yield of the final product.
In an aspect, the present invention provides an improved process for the preparation of Tembotrione of Formula (I), using cost effective and readily available reagents, such as m-xylene.
In another aspect, the present invention provides an improved process for the preparation of a Tembotrione of formula (I), comprising:
a) reacting a m-Xylene (1) compound, with a halogenating agent to obtain a compound, i.e., 1,3-dichloro-2,4-dimethylbenzene (2);
b) reacting the compound (2) in the presence of halogenating agent, a free radical and a solvent, to obtain a compound, i.e., 2-Bromomethyl-1,3-dichloro-4-methyl-benzene (3);
c) reacting the compound (3) with trifluoromethyl alcohol in presence base, to obtain a compound, i.e., 1,3-Dichloro-4-methyl-2-(2,2,2-trifluoro-ethoxymethyl)-benzene (4);
d) reacting the compound (4) with sodium thiomethoxide or methyl thiol and a base to obtain a compound, i.e., 2-Chloro-1-methyl-4-methylsulfanyl-3-(2,2,2-trifluoro-ethoxymethyl)-benzene (5);
e) oxidizing the compound (5) in the presence of an oxidizing agent to obtain a compound, i.e., 2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoro-ethoxymethyl)-benzoic acid (6);
f) converting the compound (6) to corresponding acid chloride in the presence of a halogenating agent, followed by reaction with resorcinol (7) in the presence of Lewis acid to obtain a compound, i.e., [2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoro-ethoxymethyl)-phenyl]-(2,6-dihydroxy-phenyl)-methanone (8);
g) reducing the compound-(8) in the presence of reducing agent and catalyst to obtain a target compound, i.e., Tembotrione of formula (I).
In yet another aspect, the present invention provides an improved process for the preparation of Tembotrione of Formula (I), which comprises chlorinating a compound m-Xylene (1) with chlorine gas to yield a compound 1,3-dichloro-2,4-dimethylbenzene (2), i.e.,


The compound (2), in turn is brominated using either aqueous Hydrogen Bromide (HBr) (47-49%) and aqueous hydrogen peroxide or N-bromosuccinimide in the presence of free radical initiator to obtain the compound, 2-Bromomethyl-1,3-dichloro-4-methyl-benzene (3), i.e.,

The compound (3), is treated with trifluoromethyl alcohol in presence of a base to obtain a compound, 1,3-Dichloro-4-methyl-2-(2,2,2-trifluoro-ethoxymethyl)-benzene (4), i.e.,

The compound (4), on reaction with sodium thiomethoxide or methyl thiol and a base, yields a compound, 2-Chloro-1-methyl-4-methylsulfanyl-3-(2,2,2-trifluoro-ethoxymethyl)-benzene (5), i.e.,

The compound (5), after oxidation provides a compound, 2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoro-ethoxymethyl)-benzoic acid (6), i.e.,


The compound (6), is then converted to the corresponding acid chloride after treating the acid with chlorinating agent like thionyl chloride, sulfuryl chloride, phosphorous chloride, phosphorous oxychloride and alike followed by reaction with resorcinol (7) in the presence of Lewis acid Aluminium chloride, Zinc Chloride, Ferric chloride, any metal triflates or Zeolites and alike to yield the compound, [2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoro-ethoxymethyl)-phenyl]-(2,6-dihydroxy-phenyl)-methanone (8), i.e.,

The compound (8), is then hydrogenated in the presence of hydrogen and catalysts including Pd/C or Raney Nickel or alike to furnish the target compound, Tembotrione (I)

Formula (I)
The improved process of the present invention is represented by the following (Scheme 1):
Scheme 1:

In yet another aspect, the present invention provides a process to obtain a compound (2), i.e., 1,3-dichloro-2,4-dimethylbenzene, by halogenating a compound-(1), i.e., m-xylene in the presence of a halogenating agent.
In yet another aspect, the present invention provides a process to obtain a compound-(3), i.e., 2-Bromomethyl-1,3-dichloro-4-methyl-benzene , by halogenating the compound-(2) i.e., 1,3-dichloro-2,4-dimethylbenzene, in the presence of a halogenating agent, a free radical initiator and a solvent.
In yet another aspect, the present invention provides a process to obtain a compound-(4), i.e., 1,3-Dichloro-4-methyl-2-(2,2,2-trifluoro-ethoxymethyl)-benzene, by reacting the compound-(3) i.e., 2-Bromomethyl-1,3-dichloro-4-methyl-benzene , with 2,2,2-trifluoroethan-1-ol (Trifluoroethanol) in the presence of base.
In yet another aspect, the present invention provides a process to obtain a compound-(5), i.e., 2-Chloro-1-methyl-4-methylsulfanyl-3-(2,2,2-trifluoro-ethoxymethyl)-benzene, by reacting the compound-(4) i.e., 1,3-Dichloro-4-methyl-2-(2,2,2-trifluoro-ethoxymethyl)-benzene, in the presence with sodium thiomethoxide or methyl thiol and a base.
In yet another aspect the present invention provides a process to obtain a compound-(6), i.e., 2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoro-ethoxymethyl)-benzoic acid, by oxidizing the compound-(5), i.e., 2-Chloro-1-methyl-4-methylsulfanyl-3-(2,2,2-trifluoro-ethoxymethyl)-benzene, in the presence of an oxidizing agent.
DETAILED DESCRIPTION OF THE INVENTION
At the very outset of the detailed description, it may be understood that the ensuing description only illustrates a particular form of this invention. However, such a particular form is only exemplary embodiment, and without intending to imply any limitation on the scope of this invention. Accordingly, the description is to be understood as an exemplary embodiment and teaching of the invention and not intended to be taken restrictively.
The technical solutions of the present disclosure will be further described below by way of specific embodiments. It will be apparent to those skilled in the art that the embodiments are merely illustrations of the present disclosure and should not be construed as specific limitations to the present disclosure.
It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present disclosure.
Certain ranges are presented herein with numerical values being preceded by the term “about”. The term “about” is used herein to provide literal support for the exact number that it precedes, as well as a number that is near to or approximately the number that the term precedes. In determining whether a number is near to or approximately a specifically recited number, the near or approximately unrecited number may be a number which in the context in which it is presented, provides the substantial equivalent of the specifically recited number. In an embodiment, “about” can mean within one or more standard deviations, or within ±30%, 25%, 20%, 15%, 10%, or 5% of the stated value.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the invention belongs. Although any process and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, preferred process is described. For the purposes of the present invention, the following terms are defined below:
The articles “a” and “an” are used herein to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. By way of example, “an element” means one element or more than one element.
As used herein, the terms, “including”, “includes”, “comprising”, and comprises” mean “including without limitation” and shall not be construed to limit any general statement that it follows to the specific or similar items.
Each embodiment is provided by way of explanation of the invention and not by way of limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the process described herein without departing from the scope of the invention. For instance, features illustrated or described as part of one embodiment can be applied to another embodiment to yield a still further embodiment.
While several embodiments of the present invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the functions and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the present invention.
Moreover, other than in any operating examples, or where otherwise indicated, all numbers expressing, for example, quantities of materials/ingredients used in the specification are to be understood as being modified in all instances by the term "about". The term "about" shall be interpreted to mean "approximately" or "reasonably close to" and any statistically insignificant variations therefrom.
Conventional methods for the preparation of Tembotrione are associated with drawbacks such as having impurities and a low yield of the product Tembotrione and no suggestion of high purity. Further, these conventional processes employ toxic and expensive reagents which make the process uneconomical. Still further, the conventional processes involve the use of organic bases which are harmful and difficult to separate.
In an embodiment, the present invention provides an improved process for the preparation of Tembotrione of Formula (I).
In one of the embodiments, the present invention provides am improved process for the preparation of Tembotrione of Formula (I), using cost effective, environmental friendly and readily available reagents, starting material including m-xylene.
In another aspect, the present invention provides an improved process for the preparation of a Tembotrione of formula (I), comprising:
a) reacting the compound m-Xylene (1), with a halogenating agent to obtain a compound 1,3-dichloro-2,4-dimethylbenzene (2);
b) reacting the compound (2) in the presence of halogenating agent, a free radical initiator and a solvent, to obtain a compound 2-Bromomethyl-1,3-dichloro-4-methyl-benzene (3);
c) reacting the compound (3) with trifluoromethyl alcohol in presence base, to obtain a compound 1,3-Dichloro-4-methyl-2-(2,2,2-trifluoro-ethoxymethyl)-benzene (4);
d) reacting the compound (4) with sodium thiomethoxide or methyl thiol and a base to obtain a compound 2-Chloro-1-methyl-4-methylsulfanyl-3-(2,2,2-trifluoro-ethoxymethyl)-benzene (5);
e) oxidizing the compound (5) in the presence of an oxidizing agent, obtains a compound 2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoro-ethoxymethyl)-benzoic acid (6);
f) converting the compound (6) to the corresponding acid chloride in the presence of a halogenating agent, followed by reaction with resorcinol (7) in the presence of Lewis acid to obtain a compound, [2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoro-ethoxymethyl)-phenyl]-(2,6-dihydroxy-phenyl)-methanone (8);
g) reducing the compound-(8) in the presence of reducing agent and catalyst to yield the target compound, i.e., Tembotrione of formula (I).
In one of the embodiments, the halogenating agent is selected from the group comprising of a chlorinating agent or brominating agent, fluorine, iodine, etc.
In one of the embodiments, the chlorinating agent is selected from the group comprising thionyl chloride, sulfuryl chloride, phosphorous chloride, phosphorous oxychloride, chlorine, hydrogen chloride, etc; and wherein, a brominating agent is selected from the group comprising bromine, hydrogen bromide, N-bromosuccinimide, etc; wherein the halogenating agent is combined with acetic acid, water, phosphorous and/or H2O2, or combination thereof. In a preferred embodiment, the halogenating agent is selected from the group comprising of a chlorinating agent or brominating agent.
In one of the embodiments, the radical initiator is selected from the group comprising azobisisobutyronitrile (AIBN), Benzoyl peroxide or combination thereof.
In one embodiment, the base is selected from the group comprising diisopropylamine, diisopropylethylamine, isopropyl amine, triethylamine, dimethylamine, trimethyl amine, pyridine, N-methylmorpholine, 3-picoline, 2-picoline, 4-picoline, sodium carbonate, potassium carbonate, calcium hydroxide or combination thereof.
In one of the embodiments, the suitable solvent is selected from the group comprising N,N-dimethylformamide, N-methylpyrrolidone (NMP), benzene, dichloromethane, 1,2-dichloroethane, chloroform, 1, 4-dioxane, diethyl ether, acetic acid, hydrogen peroxide, o-dichlorobenzene ethylene dichloride, carbon tetrachloride, chlorobenzene, dichlorobenzene, tetrahydrofuran and acetonitrile, ethyl acetate, acetone, dimethylsulfoxide, cyclohexane, hexane, heptane, toluene, xylene, etc or combination thereof.
In one of the embodiments, the Lewis acid is selected from the group comprising Zinc chloride (ZnCl2), Aluminium Chloride (AlCl3), Ferric Chloride (FeCl3), Boron Trifluoride (BF3), Boron Trichloride (BCl3), Titanium tetrachloride (TiCl4), Antimony Pentafluoride (SbF5), etc or combination thereof.
In one of the embodiments, the oxidizing agent is selected from the group comprising hydrogen peroxide, potassium permanganate, potassium dichromate, chlorine, sodium dichromate, chromium trioxide, nitric acid, perchloric acid, osmium tertraoxide, iodine, fluorine etc or combination thereof with or without a suitable catalyst.
In one of the embodiments, the oxidation process of the present invention is executed by utilizing oxidising agent with or without a suitable catalyst.
In one of the embodiments, the reducing agent is selected from the group comprising of sodium formate, hydrogen, oxalic acid, ascorbic acid, phosphite or combination thereof.

In one of the embodiments, the catalyst in the reaction of the present invention is selected from Pd/C or Raney Nickel, Tetrabutylammonium bromide (TBAB), Na2WO4.2H2O, (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl, (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl (TEMPO), Cobalt(II) acetate, sodium tungstate, dihydrate, Co-napthenate, palladium (II) acetate, triphenyl phosphine, or combination thereof.
In an embodiment, the reaction is carried at a pH range of 0-6, preferably at pH 3 wherein the pH may be regulated by an acid. The acid used for regulating the pH may be in concentrated form, for instance but not limited to HCl, H2SO4, HNO3, Acetic acid, etc.
In one of the embodiments, a compound (2), i.e., 1,3-dichloro-2,4-dimethylbenzene, is obtained by halogenating a compound-(1), i.e., m-xylene in the presence of a halogenating agent.
In an embodiment, the present invention provides a process for preparing a compound (2), i.e., 1,3-dichloro-2,4-dimethylbenzene, comprising addition of a solvent, for instance ethylene dichloride (EDC) into m-Xylene (1) compound, followed by addition of base such as Isopropyl amine and bubbling a halogenating agent such as Chlorine gas at slow rate at room temperature for 5 hours to 6.5 hours. Then the mixture is refluxed till completion of the reaction. The reaction is monitored and after completion, the solvent such as ethylene dichloride (EDC) is distilled off under vacuum to yield the desired product, i.e., 1,3-dichloro-2,4-dimethylbenzene (2).
In one of the embodiments, a compound-(3), i.e., 2-Bromomethyl-1,3-dichloro-4-methyl-benzene , is obtained by halogenating the compound-(2) i.e., 1,3-dichloro-2,4-dimethylbenzene, in the presence of a halogenating agent, a free radical initiator and a solvent.
In another embodiment, wherein the process for the preparation of 2-Bromomethyl-1,3-dichloro-4-methylbenzene (3) comprises two methods method A and method B.

In an embodiment, method A for a process for preparing a compound (3), i.e., 2-Bromomethyl-1,3-dichloro-4-methylbenzene, comprises addition of a solvent for instance, ethylene dichloride (EDC) to the compound (2), i.e., 1,3-dichloro-2,4-dimethylbenzene, to obtain a mixture. The mixture is stirred for 20 minutes to 30 minutes, followed by the addition of free radical initiator, for instance azobisisobutyronitrile (AIBN) and halogenating agent, such as aqueous hydrogen bromide (HBr) and aqueous hydrogen peroxide simultaneously in a dropwise manner using two different pressure equalizing addition funnels for a period of 80 minutes to 90 minutes to obtain a reaction mass, wherein, the reaction mass is heated to a temperature range of 55oC to 60oC and maintained till completion of the reaction. The reaction is monitored. After completion, the reaction mass is cooled to room temperature and quenched with sodium thiosulfate, to separate the layers, wherein, aqueous layer is washed with solvent such as ethylene dichloride (EDC) and the combined organic layer is washed with brine, dried over sodium sulfate and filtered. The organic solvent is removed to furnish a compound (3), i.e., 2-Bromomethyl-1,3-dichloro-4-methylbenzene.
In another embodiment, method B a process for preparing a compound (3), i.e., 2-Bromomethyl-1,3-dichloro-4-methylbenzene, comprises addition of a solvent, such as acetonitrile to the compound (2), i.e., 1,3-dichloro-2,4-dimethylbenzene, to obtain a mixture. The mixture is stirred for 20 minutes to 30 minutes, followed by the addition of free radical initiator, for instance azobisisobutyronitrile (AIBN) and halogenating agent such as N-Bromosuccinimide (NBS) in portions for a period of 80 minutes to 90 minutes to obtain a reaction mass. Further, the reaction mass is taken to reflux till completion. The reaction is monitored. After completion, the reaction mass is filtered, the filtrate is concentrated, wherein, the residue thus obtained is dissolved in solvent such as ethyl acetate and washed with water, and brine, and dried over sodium sulfate and filtered to remove organic solvent under vacuum to obtain a compound (3), i.e., 2-Bromomethyl-1,3-dichloro-4-methylbenzene.
In one of the embodiments, a compound-(4), i.e., 1,3-Dichloro-4-methyl-2-(2,2,2-trifluoro-ethoxymethyl)-benzene, is obtained by reacting the compound-(3) i.e., 2-Bromomethyl-1,3-dichloro-4-methyl-benzene , with 2,2,2-trifluoroethan-1-ol (Trifluoroethanol) in the presence of a base.
In an embodiment, the present invention provides a process for preparing a compound (4), i.e., 1,3-Dichloro-4-methyl-2-(2,2,2-trifluoro-ethoxymethyl)benzene, comprising adding a solvent such as Ethylene dichloride (EDC) to the compound (3), i.e., 2-Bromomethyl-1,3-dichloro-4-methylbenzene (3), to obtain a mixture. The mixture is stirred for 20 minutes to 30 minutes, followed by addition of a base such as Potassium carbonate.. Further, dropwise addition of Trifluoroethanol in a solvent such as Ethylene dichloride (EDC) at reflux temperature is performed, to obtain a reaction mass. After completion, the reaction mass is cooled to room temperature. The reaction mass is filtered and the residue is washed with a solvent such as Ethylene dichloride (EDC), wherein, the combined organic layer is washed with water, brine, and dried over sodium sulfate, and filtered under reduced pressure to furnish a compound (4), i.e., 1,3-Dichloro-4-methyl-2-(2,2,2-trifluoro-ethoxymethyl) benzene.
In one of the embodiments, a compound-(5), i.e., 2-Chloro-1-methyl-4-methylsulfanyl-3-(2,2,2-trifluoro-ethoxymethyl)-benzene, is obtained by reacting the compound-(4) i.e., 1,3-Dichloro-4-methyl-2-(2,2,2-trifluoro-ethoxymethyl)-benzene, in the presence with sodium thiomethoxide or methyl thiol and a base.
In an embodiment, the present invention provides a process for preparing a compound (5), i.e., 2-Chloro-1-methyl-4-methylsulfanyl-3-(2,2,2-trifluoro-ethoxymethyl)benzene, comprising addition of a solvent such as N,N-Dimethylformamide to the compound (4), i.e., 1,3-Dichloro-4-methyl-2-(2,2,2-trifluoro-ethoxymethyl)benzene, to obtain a mixture. The mixture is stirred for 20 minutes to 30 minutes, followed by addition of Tetrabutylammonium bromide (TBAB) and dropwise addition of aqueous Sodium thiomethoxide at a temperature range of 60oC to 70oC, to obtain a reaction mass. The reaction mass is heated at a temperature range of 110oC to 120oC. After completion, the reaction mass is cooled to room temperature and poured over ice, extracted with solvent such as ethyl acetate, by which the layers are separated, wherein, the aqueous layer is washed with a solvent such as ethyl acetate and the combined organic layer is washed with water, brine, and dried over sodium sulfate, and filtered under reduced pressure to furnish a compound (5), i.e., 2-Chloro-1-methyl-4-methylsulfanyl-3-(2,2,2-trifluoro-ethoxymethyl)benzene.
In one of the embodiments, a compound-(6), i.e., 2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoro-ethoxymethyl)-benzoic acid, is obtained by oxidizing the compound-(5), i.e., 2-Chloro-1-methyl-4-methylsulfanyl-3-(2,2,2-trifluoro-ethoxymethyl)-benzene, in the presence of an oxidizing agent.
In an embodiment, the compound (5) i.e., 2-Chloro-1-methyl-4-methylsulfanyl-3-(2,2,2-trifluoro-ethoxymethyl)-benzene, is oxidized using a strong oxidising agent which will oxidize CH3 (Methyl) group to the corresponding -COOH group and sulfide to the corresponding sulfone both concurrently furnishing compound (6).
In an embodiment, the present invention provides a process for preparing a compound (6), i.e., 2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoro-ethoxymethyl)benzoic acid, comprising addition of water to the compound (5), i.e., 2-Chloro-1-methyl-4-methylsulfanyl-3-(2,2,2-trifluoro-ethoxymethyl)benzene. Followed by addition of Potassium permanganate dissolved in water for a period of 2.5 hours to 3 hours at reflux to obtain a reflux mass. Further, around 1600-1700 mL water is distilled off under vacuum by down-ward distillation. After water removal, the reaction mass is cooled to room temperature and extracted with solvent such as ethyl acetate to separate the layers, wherein, the aqueous layer is washed with solvent such as ethyl acetate and the combined organic layer is washed with water, brine, and dried over sodium sulfate, and filtered under reduced pressure to furnish a compound (6), i.e., 2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoro-ethoxymethyl)benzoic acid.
In an embodiment, the reaction is carried at a temperature of from 0? to 200? for a period of about 1 hour to about 24 hours and at a pressure of from an atmospheric pressure to 50 bar.
In an embodiment, the present invention provides a process for preparing a compound (8), i.e., [2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoroethoxymethyl)-phenyl]-(2,6-dihydroxyphenyl)-methanone, comprising adding a solvent such as Ethylene dichloride to the compound (6), i.e., 2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoro-ethoxymethyl)benzoic acid, followed by the addition of a solvent such as N,N-Dimethyl formamide to obtain a reaction mass which is stirred for 15 minutes to 20 minutes to obtain a mixture. Thionyl chloride is added dropwise at room temperature to the mixture to obtain a reaction mass. After complete addition, the reaction mass is heated to 70oC till clear solution is obtained. After completion of the reaction, the solvent and excess thionyl chloride is distilled out to provide the corresponding an acyl chloride.
In another embodiment, the solvent such as Ethylene dichloride is added to the acyl chloride as obtained above. The reaction mass is cooled to a temperature range of 0oC to 10oC. Further, copper (II) triflate.and Lewis acid such as Aluminium chloride are added portion wise. The reaction is stirred at the same temperature till the completion of the reaction. After completion, the reaction mass is slowly poured on crushed ice with vigorous stirring to separate the organic layer and the aqueous layer is further washed with the solvent such as Ethylene chloride and the combined organic layer is washed with water, brine, and dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure to furnish a compound (8), i.e., [2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoroethoxymethyl)-phenyl]-(2,6-dihydroxyphenyl)-methanone.
In an embodiment, the present invention provides an improved process for preparing a Tembotrione of Formula (I), i.e., 2-[2-chloro-4-methylsulfonyl-3-(2,2,2-trifluoroethoxymethyl) benzoyl]cyclohexane-1,3-dione, comprising: adding water and sodium formate to the compound (8), i.e., [2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoroethoxymethyl)-phenyl]-(2,6-dihydroxyphenyl)-methanone to obtain a reaction mass. The reaction mixture is heated to a temperature range of 30oC to 40oC. At this temperature, a slow nitrogen stream is passed through the reaction mass for 20 minutes to 30 minutes, further, a catalyst such as wet Pd/C is added and the temperature is elevated to 50oC and stirred till completion of the reaction. The hot reaction mass is filtered to remove the catalyst for reuse. The filtrate is cooled to 0oC to 5oC and acidified to pH 3 with Conc. Hydrochloric acid to obtain solid. The solid obtained is filtered to furnish a crude product, i.e., 2-[2-chloro-4-methylsulfonyl-3-(2,2,2-trifluoroethoxymethyl)benzoyl]cyclohexane-1,3-dione, Tembotrione (I), wherein, the material is purified by crystallization.
The improved process for preparing Tembotrione of formula (I) disclosed according to the present invention yields Tembotrione with purity of around 95% to 99% and a yield of above 80%.
The present invention has the advantage of short residence time of the material, high selectivity, high yield, high purity, less equipment investment, manufacturing cost savings, reduced material consumption, reducing the amount of by-products in the final product. Accordingly, the entire process is technically advanced over the conventional process, continuous, low energy consumption, an efficient and feasible synthesis of Tembotrione of formula (I). Thus, present process is simple, rapid and industrially viable. Thus, the present invention involves technical advance as compared to the existing knowledge or having economic significance or both and that makes the invention not obvious to a person skilled in the art.
In some embodiments, the purity is determined by high-performance liquid chromatography (HPLC) analysis.
The process of the present invention involves m-xylene as a starting material as m-xylene is provides production of fine chemical products and intermediates.
The use of m-xylene as a starting material for preparation of Tembotrione (I) results in an improved production of final product with higher yield, along with high purity and stability of Tembotrione (I).
The improved process of the present disclosure is simple, employs cost effective and less toxic reagents and provides tembotrione with a comparatively high purity and high yield.
According to another aspect, there is provided an improved process for preparing agrochemical composition comprising highly pure and stable Tembotrione obtained as per the process disclosed herein.
Yet in another embodiment, agrochemical compositions comprise at least a bio-active effective amount of highly pure and stable Tembotrione obtained by the improved processes disclosed herein. The agrochemical compositions further contain one or more agrochemically acceptable excipients. Suitable excipients and the amounts to use may be readily determined by the formulation scientist based upon experience and consideration of standard procedures and reference works in the field.
While preferred embodiments and examples have been shown and described, it is to be understood that various further modifications will be apparent to those skilled in the art.
EXAMPLES
Although the content of the present invention is further specifically explained using examples, the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded. The following examples are presented to further explain the invention with experimental conditions, which are purely illustrative and are not intended to limit the scope of the invention.
Tembotrione (Formula I) was synthesized by sequential reactions starting from compound m-xylene i.e., compound-(1). Thereafter, the compound-(1) was subjected to chlorination using chlorinating agents including but not limited to chlorine gas to yield a compound (2). The compound (2), is then brominated in the presence of aqueous Hydrogen Bromide (47-49%) and aqueous hydrogen peroxide or N-bromosuccinimide, Bromine in acetic acid, Bromine in water, and alike in the presence of free radical initiator and solvents including but not limited to ethylene dichloride, acetonitrile, carbon tetrachloride, chlorobenzene, o-dichlorobenzene to obtain a compound (3), the said chlorination and bromination are carried out at a temperature of from 0oC to 180oC for a period ranging from 1 hour to 24 hours. The more preferred temperature range is from 25oC to 180oC and at pressure of from an atmospheric pressure to 10 bar.
The compound (3), is then treated with trifluoroethanol in presence of a base to obtain a compound (4). The compound (4), on reaction with sodium thiomethoxide or methyl thiol and a base, yields a compound (5). The compound (5) on oxidation in the presence of oxidizing agent and a suitable catalyst provides a compound (6), which in turn is converted to the corresponding acid chloride after treating the acid with chlorinating agent like thionyl chloride, sulfuryl chloride, phosphorous chloride, phosphorous oxychloride and alike followed by reaction with resorcinol (7) in the presence of Lewis acid such as Aluminium chloride, Zinc Chloride, Ferric chloride, any metal triflates or Zeolites, metal triflates and alike to furnish a compound (8). The said reaction is carried out at a temperature of from 0oC to 200oC for a period of 1 hour to 24 hours. The more preferred temperature range is from 25oC to 200oC and at pressure of from an atmospheric pressure to 10 bar.
The compound (8), is hydrogenated in the presence of hydrogen and catalysts including Pd/C or Raney Nickel or alike to yield a target compound, Tembotrione of formula (I).
The selected starting material is optimally substituted to get desired selectivity and improved yield for the proposed scheme.
The following is the reaction scheme of the present invention:

SCHEME-1
Example 1: Preparation of 1,3-dichloro-2,4-dimethylbenzene (2)

A four necked glass reactor (2 Lit) fitted with condenser, thermometer pocket, thermometer, mechanical stirrer was charged with ethylene dichloride (EDC) (575 mL) followed by m-Xylene (220 g). Isopropyl amine (2.2 g) was added. Chlorine gas was bubbled at slow rate at room temperature for 6.5 hours. Then the mixture was refluxed till completion of the reaction. The reaction was monitored. After completion, ethylene dichloride (EDC) was distilled off under vacuum to yield the desired product, 1,3-dichloro-2,4-dimethylbenzene (2). After purification, HPLC purity (area) : 95%, and Yield: 268.8 g, 78 %.
Example 2: Preparation of 2-Bromomethyl-1,3-dichloro-4-methylbenzene (3)

Method A:
A four necked glass reactor (2 Lit) fitted with condenser, thermometer pocket, thermometer, mechanical stirrer was charged with ethylene dichloride (EDC) (600 mL) followed by 1,3-dichloro-2,4-dimethylbenzene (2). The mixture was stirred for 30 minutes. azobisisobutyronitrile (AIBN) (9.2 g) was added. Aqueous hydrogen bromide (HBr) (48%, 273.7 g) and Aqueous Hydrogen peroxide (30%, 178 g) were added simultaneously in a dropwise manner from using two different pressure equalizing addition funnels over a period of 80 minutes to 90 minutes. After complete addition, the reaction mass was taken to 55oC to 60oC and maintained till completion of the reaction. The reaction was monitored. After completion, the reaction mass was cooled to room temperature and quenched with sodium thiosulfate. The layers were separated. Aqueous layer was washed with ethylene dichloride (EDC) (2 X 100 mL). The combined organic layer was washed with brine, dried over sodium sulfate and filtered. The organic solvent was removed to furnish 2-Bromomethyl-1,3-dichloro-4-methylbenzene (3). After purification, HPLC purity (area): 94%, Yield: 238.6 g, 70 %.
Method B:
A four necked glass reactor (2 Lit) fitted with condenser, thermometer pocket, thermometer, mechanical stirrer was charged with Acetonitrile (600 mL) followed by 1,3-dichloro-2,4-dimethylbenzene (2). The mixture was stirred for 30 minutes. azobisisobutyronitrile (AIBN) (7.8 g) was added. N-Bromosuccinimide (NBS) (241.1 g) was added in portions over a period of 90 minutes. After complete addition of NBS, the reaction mass is taken to reflux. The reaction was maintained at reflux till completion. The reaction was monitored. After completion, the reaction mass was filtered, the filtrate was concentrated. The residue thus obtained was dissolved in Ethyl acetate and washed with water, brine, dried over sodium sulfate and filtered. Organic solvent was removed under vacuum to provide 2-Bromomethyl-1,3-dichloro-4-methylbenzene (3). After purification, HPLC purity (area): 96%, Yield: 222.8 g, 80 %.
Example 3: Preparation of 1,3-Dichloro-4-methyl-2-(2,2,2-trifluoro-ethoxymethyl)benzene (4)

A four necked glass reactor (2 Lit) fitted with condenser, thermometer pocket, thermometer, mechanical stirrer was charged with Ethylene dichloride (EDC) (570 mL) followed by 2-Bromomethyl-1,3-dichloro-4-methylbenzene (3). The mixture was stirred for 30 minutes. Potassium carbonate (231.8 g) was added in one lot. Tetrabutylammonium bromide (TBAB) (12.7 g) was added. Trifluoroethanol (80.2 g) in ethylene dichloride (EDC) (160 mL) was added dropwise at reflux temperature. The reaction was monitored by HPLC. After completion, the reaction mass was cooled to room temperature. The reaction mass was filtered and the residue was washed with ethylene dichloride (EDC) (2 X 75 mL). The combined organic layer was washed with water, brine, dried over sodium sulfate, and filtered. The organic layer was concentrated under reduced pressure to furnish 1,3-Dichloro-4-methyl-2-(2,2,2-trifluoro-ethoxymethyl) benzene (4). After purification, HPLC purity (area): 95%, Yield: 166.9 g, 86 %.
Example 4: Preparation of 2-Chloro-1-methyl-4-methylsulfanyl-3-(2,2,2-trifluoro-ethoxymethyl)benzene (5)

A four necked glass reactor (1 Lit) fitted with condenser, thermometer pocket, thermometer, mechanical stirrer was charged with N,N-Dimethylformamide (150 mL) followed by 1,3-Dichloro-4-methyl-2-(2,2,2-trifluoro-ethoxymethyl)benzene (4). The mixture was stirred for 30 minutes. Tetrabutylammonium bromide (TBAB) (9.4 g) was added. Aqueous Sodium thiomethoxide (20%, 240.6 g) was added dropwise at 60oC to 70oC. After complete addition of sodium thiomethoxide, the reaction mass heated at 110oC to 120oC. The reaction was monitored by HPLC. After completion, the reaction mass was cooled to room temperature and poured over ice, extracted with ethyl acetate. The layers were separated. The aqueous layer was washed with ethyl acetate (2 X 100 mL). The combined organic layer was washed with water, brine, dried over sodium sulfate, and filtered. The organic layer was concentrated under reduced pressure to furnish 2-Chloro-1-methyl-4-methylsulfanyl-3-(2,2,2-trifluoro-ethoxymethyl)benzene (5). After purification, HPLC purity (area): 95%, Yield: 142.6 g, 96 %.
Example 5: Preparation of 2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoro-ethoxymethyl)benzoic acid (6)

A four necked glass reactor (5 Lit) fitted with condenser, thermometer pocket, thermometer, mechanical stirrer was charged with water (1000 mL) followed by 2-Chloro-1-methyl-4-methylsulfanyl-3-(2,2,2-trifluoro-ethoxymethyl)benzene (5). Potassium permanganate (614.6 g) dissolved in water was added dropwise over a period of 2.5 hours to 3 hours at reflux. The reaction was monitored by HPLC. After completion, around 1600-1700 mL water was distilled off under vacuum by down-ward distillation. After water removal, the reaction mass was cooled to room temperature and extracted with Ethyl acetate. The layers were separated. The aqueous layer was wished with ethyl acetate (2 X 100 mL). The combined organic layer was washed with water, brine, dried over sodium sulfate, and filtered. The organic layer was concentrated under reduced pressure to furnish 2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoro-ethoxymethyl)benzoic acid (6). After purification, HPLC purity (area): 95%, Yield: 161.6 g, 55 %.
Example 6: Preparation of [2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoroethoxymethyl)-phenyl]-(2,6-dihydroxyphenyl)-methanone (8)

A three necked glass reactor (1 Lit) fitted with condenser, thermometer pocket, thermometer, mechanical stirrer was charged with Ethylene dichloride (450 mL) followed by 2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoro-ethoxymethyl)benzoic acid (6) (152.63 g). N,N-Dimethyl formamide ((0.68 g) was added and the reaction mass was stirred for 15minutes to 20 minutes. Thionyl chloride (71.1 g) was added dropwise at room temperature. After complete addition, the reaction mass was heated to 70oC till clear solution. After completion of the reaction, the solvent and excess thionyl chloride was distilled out to provide the corresponding acyl chloride.
In another three necked glass reactor (1 Lit) fitted with condenser, thermometer pocket, thermometer, mechanical stirrer was charged with Ethylene dichloride (450 mL) followed by the acyl chloride (in 100 mL of Ethylene chloride) obtained. The reaction mass was cooled to 0oC to 10oC. Copper (II) triflate (2.2 mol%) was added. Aluminium chloride (46.4 g) was added portion wise. The reaction was stirred at the same temperature till the completion of the reaction. After completion, the reaction mass was slowly poured on crushed ice (~550 g) with vigorous stirring. The organic layer was separated. The aqueous layer was washed with Ethylene chloride (2 X 100 mL). The combined organic layer was washed with water, brine, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure to furnish [2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoroethoxymethyl)-phenyl]-(2,6-dihydroxyphenyl)-methanone (8). After purification, HPLC purity: 95%, Yield: 111.3 g, 90 %.
Example 7: Preparation of 2-[2-chloro-4-methylsulfonyl-3-(2,2,2-trifluoroethoxymethyl) benzoyl]cyclohexane-1,3-dione, Tembotrione (I)

A three necked glass reactor (0.5 Lit) fitted with condenser, thermometer pocket, thermometer, mechanical stirrer was charged with Water (250 mL) followed by [2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoroethoxymethyl)-phenyl]-(2,6-dihydroxyphenyl)-methanone (8) (100 g) and sodium formate (21.35 g). The reaction mixture was heated to 40oC. At this temperature, a slow nitrogen stream is passed through the reaction mass for 30 minutes. Wet 10 % Pd/C (1.85 g) was added at this temperature. After addition, the temperature was elevated to 50oC and stirred till completion of the reaction. The hot reaction mass was filtered to remove the catalyst for reuse. The filtrate was cooled to 0oC to 5oC and acidified to pH 3 with Conc. Hydrochloric acid (HCl). The solid obtained was filtered to furnish crude 2-[2-chloro-4-methylsulfonyl-3-(2,2,2-trifluoroethoxymethyl)benzoyl]cyclohexane-1,3-dione, Tembotrione (I). The material is purified by crystallization. After purification, HPLC purity: 98 %, Yield: 82.7 g, 84 %.
Although this invention has been disclosed in the context of certain preferred embodiments and examples, it will be understood by those skilled in the art that the present invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof.
It should be understood that the scope of the present invention is not limited by the examples in any manner. It will be appreciated by any person skilled in this art that the present invention includes the given examples and further can be modified and altered without departing from the novel teachings and advantages of the invention which are intended to be included within the scope of the invention.
,CLAIMS:I/WE CLAIM:
1. An improved process for the preparation of a Tembotrione of formula (I), comprising:
a) reacting a compound m-Xylene (1), with a halogenating agent to obtain a compound 1,3-dichloro-2,4-dimethylbenzene (2);
b) reacting the compound (2`) in the presence of halogenating agent, a free radical initiator and a solvent, to obtain a compound 2-Bromomethyl-1,3-dichloro-4-methyl-benzene (3);
c) reacting the compound (3) with solvent in presence base, to obtain a compound 1,3-Dichloro-4-methyl-2-(2,2,2-trifluoro-ethoxymethyl)-benzene (4);
d) reacting the compound (4) with sodium thiomethoxide or methyl thiol and a base to obtain a compound 2-Chloro-1-methyl-4-methylsulfanyl-3-(2,2,2-trifluoro-ethoxymethyl)-benzene (5);
e) oxidizing the compound (5) in the presence of an oxidizing agent, obtains a compound 2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoro-ethoxymethyl)-benzoic acid (6);
f) converting the compound (6) to the corresponding acid chloride in the presence of a halogenating agent, followed by reaction with resorcinol (7) in the presence of Lewis acid to obtain a compound, [2-Chloro-4-methanesulfonyl-3-(2,2,2-trifluoro-ethoxymethyl)-phenyl]-(2,6-dihydroxy-phenyl)-methanone (8);
g) reducing the compound-(8) in the presence of reducing agent and catalyst to yield a target compound, i.e., Tembotrione of formula (I).

2. The improved process as claimed in claim 1, wherein, the halogenating agent is selected from the group comprising of a chlorinating agent, brominating agent, fluorine, iodine, etc. or combination thereof.

3. The improved process as claimed in claim 2, wherein, the chlorinating agent is selected from the group comprising thionyl chloride, sulfuryl chloride, phosphorous chloride, phosphorous oxychloride, chlorine, hydrogen chloride, etc. or combination thereof.

4. The improved process as claimed in claim 2, wherein, a brominating agent is selected from the group comprising bromine, hydrogen bromide, N-bromosuccinimide, etc. or combination thereof.

5. The improved process as claimed in claims 1-4, wherein, the halogenating agent is combined with acetic acid, water, hydrogen, phosphorous and/or H2O2, or combination thereof.

6. The improved process as claimed in claim 1, wherein, the free-radical initiator is selected from the group comprising azobisisobutyronitrile (AIBN), Benzoyl peroxide or combination thereof.

7. The improved process as claimed in claim 1, wherein, the base is selected from the group comprising diisopropylamine, diisopropylethylamine, isopropyl amine, triethylamine, dimethylamine, trimethyl amine, pyridine, N-methylmorpholine, 3-picoline, 2-picoline, 4-picoline, sodium carbonate, potassium carbonate, calcium hydroxide or combination thereof.

8. The improved process as claimed in claim 1, wherein, the solvent is selected from the group comprising N,N-dimethylformamide, N-methylpyrrolidone (NMP), benzene, dichloromethane, 1,2-dichloroethane, chloroform, 1, 4-dioxane, diethyl ether, acetic acid, , o-dichlorobenzene, ethylene dichloride, carbon tetrachloride, chlorobenzene, dichlorobenzene, tetrahydrofuran and acetonitrile, ethyl acetate, acetone, dimethylsulfoxide, cyclohexane, hexane, heptane, toluene, xylene, or combination thereof.

9. The improved process as claimed in claim 1, wherein, the Lewis acid is selected from the group comprising Zinc chloride (ZnCl2), Aluminium Chloride (AlCl3), Ferric Chloride (FeCl3), Boron Trifluoride (BF3), Boron Trichloride (BCl3), Titanium tetrachloride (TiCl4), Antimony Pentafluoride (SbF5), etc. or combination thereof.

10. The improved process as claimed in claim 1, wherein, the oxidizing agent is selected from the group comprising hydrogen peroxide, potassium permanganate, potassium dichromate, chlorine, sodium dichromate, chromium trioxide, nitric acid, perchloric acid, osmium tertraoxide, etc or combination thereof with or without a suitable catalyst.

11. The improved process as claimed in claim 1, wherein, the reducing agent is selected from the group comprising of sodium formate, hydrogen, oxalic acid, ascorbic acid, phosphite or combination thereof.

12. The improved process as claimed in claim 1, wherein, the catalyst in the reaction of the present invention is selected from Pd/C, Raney Nickel, Pt/C, Tetrabutylammonium bromide, Na2WO4.2H2O, (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl or (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl (TEMPO), Sodium tungstate, dihydrate, Cobalt(II) acetate, Co-napthenate, palladium (II) acetate, triphenyl phosphine, or combination thereof.

13. The improved process as claimed in claim 1, wherein, the reaction is carried at a temperature of from 0? to 200?.

14. The improved process as claimed in claim 1, wherein the reaction is carried out for a period of about 1 hour to about 24 hours and at a pressure of from an atmospheric pressure to 50 bar.

15. An agrochemical composition, wherein the composition comprises at least a bio-active effective amount of Tembotrione of formula (I) as obtained by the process claimed in claims 1-13.

16. The agrochemical composition as claimed in claim 15, wherein the composition further comprises one or more agrochemically acceptable excipients.

17. A process for preparing the agrochemical composition comprising Tembotrione of formula (I) as claimed in claims 15-16.