DESC:FORM 2
THE PATENT ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)

“AN INDUSTRIAL PROCESS FOR THE PREPARATION OF 3-BROMO-1-(3-CHLOROPYRIDIN-2-YL)-1H-PYRAZOL-5-CARBOXYLIC ACID”

Hikal Limited, an Indian company, of 3A & 3B, International Biotech Park, Hinjewadi, Pune – 411 057, India

The following specification particularly describe the invention and the manner in which it is to be performed.

RELATED APPLICATION

This application claims the benefit to Indian Provisional Application No.IN 202121034632, filed on August 02, 2021, the contents of which is incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to an industrial process for the preparation of 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid of formula (I). The present invention further involve the preparation of 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid of formula (I) using an intermediate of formula(V).


BACKGROUND OF THE INVENTION

3-Bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid is a key intermediate for the preparation of crop protection agents particularly insecticide anthranil amides such as Cyantraniliprole, Chlorantraniliprole, Cyclaniliprole.

Several publications such as US6965032B2, US7232836B2, US7335780B2, IN201721000978A, CN110684012A, have disclosed the process for preparation of 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid. Various publications such as WO2008134969A1, IN201721000978A, CN102249991A, CN107778225Ahave disclosed the preparation of intermediates of 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid such as 3-chloro-2-hydrazinyl-pyridine. The known processes, however, have one or the other disadvantages, those as mentioned below: (i) involve more reaction steps; (ii) reaction at extreme temperature; (iii) expensive and hazardous reagent or catalyst (iv) low process yield; (v) more cycle time; (vi) tedious operations; (vii) more effluent generation. Thus, the processes are not an industrially advantageous.

The need remains for an alternative method using low-cost, industrially available reagents and to overcome the limitations of the processes known in the art, the inventors of the present invention have developed a process for preparation of3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid.

SUMMARY OF THE INVENTION

In one aspect, the present invention relates to an improved process for the preparation of 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid of formula (I).

In another aspect, the present invention relates to a process for the preparation of 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid of formula (I)using an intermediate of formula (V).

In another aspect, the present invention relates to an intermediate of formula (V).

In another aspect, the present invention relates to a process for the preparation of 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid of formula (I) where the process comprises the steps of:
a) reacting a compound of formula (IV) with 2-nitrobenzenesulfonyl chloride in presence of base, solvent to obtain a compound of formula (V);

b) reacting a compound of formula (V) with brominating agent in solvent to obtain a compound of formula (VI);

c) reacting a compound of formula (VI) with oxidizing agent in solvent to obtain a compound of formula (VII);

d) hydrolysing a compound of formula (VII) to obtain 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid of formula (I).

In another aspect, the present invention relates to a process for the preparation of 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid of formula (I)where the process comprises the steps of:
a) reacting a compound of formula (IV) with brominating agent, and oxidizing agent, in a solvent without isolation of compound formula (VI) to obtain a compound of formula (VII);

b) hydrolysing a compound of formula (VII) to obtain 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid of formula (I).

In another aspect, the present invention relates to a process for the preparation compound formula (IV) where the process comprising steps of:
a) reacting 2,3-dichloropyridine (II) with hydrazine hydrate with or without base in solvent to obtain 3-chloro-2-hydrazino-pyridine (III), wherein base isselected from sodium carbonate, potassium carbonate, sodium bicarbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, and potassium bicarbonate; and
b) reacting compound formula (III) with dialkyl maleate, alkali metal alkoxide, in presence of an acid and solvent.

In another aspect, the present invention relates to a process for the preparation of 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid of formula (I)where the process comprises the steps of:
a) reacting 2,3-dichloropyridine (II) with hydrazine hydrate with or without base in solvent to obtain 3-chloro-2-hydrazino-pyridine (III);

b) reacting3-chloro-2-hydrazino-pyridine (III) with dialkyl maleate in presence of alkali metal alkoxide, an acid, solvent to obtain compound of formula (IV);

c) reacting compound of formula (IV)with brominating agent,and an oxidizing agent in solvent without isolating compound (VI)to obtain compound of formula (VII);

d) hydrolysing a compound of formula (VII) to obtain 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid of formula (I).

In another aspect, the present invention relates to an intermediate of formula (V).

In another aspect, the present invention relates to a process for the preparation of compound of formula (V) which comprises reacting a compound of formula (IV) with 2-nitrobenzenesulfonyl chloride in presence of a base in solvent to obtain compound of formula (V).

In another aspect, the present invention relates to a process for the preparation of 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid of formula (I) where the process comprises the steps of:
a) reacting 2,3-dichloropyridine(II) with hydrazine hydrate with or without base in solvent to obtain 3-chloro-2-hydrazino-pyridine(III);

b) reacting3-chloro-2-hydrazino-pyridine (III) with dialkylmaleate in presence of alkali metal alkoxide, acid insolvent to obtain compound of formula (IV);

c) reacting compound of formula (IV) with 2-nitrobenzenesulfonyl chloride in presence of base in solvent to obtain a compound of formula (V);

d) reacting compound of formula (V) with brominating agent in solvent to obtain a compound of formula (VI);

e) oxidizing compound of formula (VI) with an oxidizing agent in solvent to obtain a compound of formula (VII);

f) hydrolysing a compound of formula (VII) to obtain 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid of formula (I).

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more detail hereinafter. The invention may be embodied in different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. As used in the specification, and in the appended claims, the singular forms “a,” “an,” “the,” include plural referents unless the context clearly indicates otherwise.

The term solvent used herein, refers to the single solvent or mixture of solvents.

In one embodiment the process for preparation of compound of formula (I) is illustrated as shown in below synthetic scheme 1.

Scheme-1

The process for the preparation of 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid of formula (I) is illustrated in the following synthetic scheme-2.
Scheme-2

The process for the preparation of compound of formula (IV) is illustrated in the following synthetic scheme 3.

Scheme-3

In an embodiment, the instant invention provides the preparation of 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid of formula (I), wherein one or more steps is performed in in-situ manner or the one or more intermediate is not isolated, which makes present process more economic.

In another embodiment of the present invention, wherein the preparation of 3-chloro-2-hydrazinyl-pyridine (III) is carried out with or without base.

In another embodiment of the present invention, wherein the said base used for the preparation of compound (III) and compound (V)is selected from sodium carbonate, potassium carbonate, sodium bicarbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, potassium bicarbonate, triethylamine, diethylamine, N,N-diisopropylethylamine, 4-(dimethylamino)pyridine, ammonia, and pyridine.

In another embodiment of the present invention, wherein the hydrazine hydrate used for the preparation of compound (III) is 60% to 80%.

In another embodiment of the present invention, wherein the preparation of compound (III) involved the removal of water by simple technique such as dean stark apparatus, which reduces overall reaction time, thus the process is more efficient and commercially viable.

In another embodiment of the present invention, wherein the solvent used for the preparation of compound (III) is recycled and reused.

In another embodiment of the present invention, wherein compound formula (VII) is obtained by bromination and oxidation of compound of formula (IV) without isolation of compound formula (VI).

In another embodiment of the present invention, wherein compound formula (VII); is obtained by reacting compound formula (IV) with 2-nitrobenzenesulfonyl chloride to obtain compound formula (V) and further reacting with brominating and oxidizing agent.

In another embodiment of the present invention, wherein the said dialkyl maleate is selected from dimethyl maleate, diethyl maleate, dipropyl maleate and dibutyl maleate.

In another embodiment of the present invention, wherein the said metal alkoxide is selected from sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium tert-butoxide, potassium methoxide, potassium ethoxide, and lithium tert-butoxide.

In another embodiment of the present invention, wherein compound of formula (IV) is treated with solvent water, ethyl acetate and Isopar-G.

In another embodiment of the present invention, wherein the said acid is selected from formic acid, acetic acid, hydrochloric acid, sulfuric acid, phosphoric acid, and the like.

In another embodiment of the present invention, wherein the brominating agent is selected from hydrogen bromide, hydrogen bromide in acetic acid, bromine, N-bromosuccinimide, and phosphorus oxybromide.

In another embodiment of the invention wherein, the compound of formula (VI) is used as such without isolation for next stage.

In another embodiment of the invention wherein, the compound of formula (VI) is in hydrocarbon solvent, which is selected from hexane, heptane, toluene, xylene, cyclohexane, preferably toluene.

In another embodiment of the present invention, wherein the oxidizing agent is selected from sodium persulfate, potassium persulfate, sodium perborate, hydrogen peroxide, organic peroxides, ammonium persulfate, potassium monopersulfate, and potassium permanganate.

In another embodiment of the present invention, wherein the oxidization of the compound of formula (VI) is performed using oxidizing agent optionally in the presence of acid.

In another embodiment of the present invention, wherein the compound of formula (VII) is obtained by simple filtration technique instead of tedious distillation and purification processes.

In another embodiment of the present invention, wherein the hydrolysis of compound of formula (VII) is performed by using acid or base in a solvent.

In another embodiment of the invention wherein, the solvent for preparation of compounds of formula (III), (IV), (V), (VI), and (I) is selected from water; alcoholic solvents such as methanol, ethanol, propanol, isopropanol, n-butanol; ketonic solvents such as acetone, methyl isobutyl ketone, ethyl methyl ketone and n-butanone; ether solvents such as diethyl ether, diisopropyl ether, methyl-t-butyl ether, methoxybenzene; ester solvents such as ethyl acetate, n- propyl acetate, n-butyl acetate; hydrocarbons such as hexane, heptane, toluene, xylene, cyclohexane; dichloromethane (DCM), ethylene dichloride, tetrahydrofuran (THF), acetonitrile, propionitrile, andmethylene bromide.

In another embodiment of the invention wherein, the solvent for preparation of compound of formula (VII) is selected from polar aprotic solvent such as acetonitrile, propionitrile, dimethylformamide (DMF), dimethyl sulfoxide (DMSO).

In another embodiment of the invention wherein, the reaction step for preparation of 3-chloro-2-hydrazino-pyridine (III) is performed at reflux temperature and reaction mixture is cooled at 20°C to 30°C.

In another embodiment of the invention wherein, the reaction step for preparation compound of formula (IV) is performed at temperature 60°C to 75°C.

In another embodiment of the invention wherein, the reaction step for preparation compound of formula (V) is performed at temperature 5°C to 10°C.

In another embodiment of the invention wherein, the reaction step for preparation of compound of formula (VI) and formula (VII) is performed at temperature 50°C to 80°C.

In another embodiment of the invention wherein, the reaction step for preparation of compound of formula (I) is performed at temperature 20°C to 30°C.

The preparation of the starting materials and reagents used in the present invention are well known in prior art.

The invention is further illustrated by the following examples, which should not be construed to limit the scope of the invention in anyway.

EXPERIMENTAL

Example-1.0: Preparation of 3-chloro-2-hydrazino-pyridine (III)
In a round bottom flask (RBF), 2,3-dichloropyridine (II) (1.0 eq), anhydrous potassium carbonate (0.5 eq.) and n-butanol (2.0 vol) were charged at 20°C to 30°C. To this, hydrazine hydrate (2.0 eq) was added and heated to reflux temperature and water(10% to 50%) was collected using dean stark apparatus up to 21 h. The completion of reaction was monitored by HPLC, and reaction mixture was cooled to 25°Cto30°C. To the reaction mixture water (2-5 vol) was added and maintained for 30 min. The reaction mixture was filtered, the wet cake was washed with n-butanol and the solid was dried to get white crystals of 3-chloro-2-hydrazinyl-pyridine of formula (III)(Yield:92-94%,Assay:99.5%).

Example-1.1: Preparation of 3-chloro-2-hydrazino-pyridine (III)

In a cylindrical reactor, 2,3-dichloropyridine (II) 2.5 Kg (0.017 k mole,1.0 eq), anhydrous potassium carbonate (0.5-1.0 eq.) and n-butanol (2.0-4.0vol) were charged at 20°C to 30°C. To this, hydrazine hydrate (2.0-4.0 eq) was added and heated to reflux temperature and water (10% to 50%) was collected using dean stark apparatus up to 18-28 h. The completion of reaction was monitored by HPLC, and reaction mixture was cooled to 25°C to 30°C. To the reaction mixture water (2-5 vol.) was added and maintained for 30 min. The reaction mixture was filtered, the wet cake was washed with n-butanol (0.5-0.6vol) and the solid was dried to get white crystals of 3-chloro-2-hydrazinyl-pyridine of formula (III) (Yield: 94-96%, Assay: >99.5%).

Example-2.0: Preparation of compound of formula (IV)
In RBF, sodium ethoxide (1.3 eq), ethanol (6-8 vol) and 3-chloro-2-hydrazinyl-pyridine of formula (III) (1.0 eq) were charged at RT. The reaction mixture was heated to reflux temperature to get the clear solution. To the reaction mixture, diethylmaleate (1.1-1.5 eq) was slowly added for30 min at 70°C to 75°C maintained for 1.0 h. The completion of reaction was monitored by HPLC, after completion reaction mixture was cooled to 60°C to 65°C and pH of reaction mixture was maintained in range 6.0 to 8.0and stirred for 30 min. The reaction mixture was cooled to 50°C to 55°C and simultaneously ethanol was removed under vacuum. To the reaction mass was treated with, water (2-6 vol) was charged, followed by ethyl acetate (2-5 vol), and then Isopar-G (1-2 vol).The reaction mixture was cooled at0°Cto30°C and maintained for 1-2 h. The reaction mixture was filtered, the wet cake was washed with aqueous ethanol and further dried to get off-white to pale yellow powder compound of formula (IV) (Yield: 76%, Assay -98%).

Example-2.1: Preparation of compound of formula (IV)
In a cylindrical reactor, sodium ethoxide 1.38 Kg (1.3 eq), ethanol (6-8 vol) and 3-chloro-2-hydrazinyl-pyridine of formula (III) (1.0-1.2 eq) were charged at RT. The reaction mixture was heated to reflux temperature to get the clear solution. To the reaction mixture, diethyl maleate (1.2-1.4 eq) was slowly added for 30 min at 70°C to 75°C maintained for 1.0 h. The completion of reaction was monitored by HPLC, after completion reaction mixture was cooled to 60°C to 65°C and pH of reaction mixture was maintained in range 6.0 to 8.0 and stirred for 30 min. The reaction mixture was cooled to 50°C to 55°C and simultaneously ethanol was removed under vacuum. To the reaction mass was treated with, water (2.0-6.0 vol) was charged, followed by ethyl acetate (2.0-5.0 vol), and then Isopar-G (1.0-2.0 vol). The reaction mixture was cooled at 0°C to 30°C and maintained for 1-2 h. The reaction mixture was filtered, the wet cake was washed with aqueous ethanol and further dried to get off-white to pale yellow powder compound of formula (IV) (Yield: 78-82%, Assay >98%).

Example-3.0: Preparation of compound of formula (V)
In RBF, compound of formula (IV) (1.0 eq), acetone (2.0-5.0 vol) and TEA (1.7-2.0 eq) were charged, maintained for 10 min, and cooled at 5°C to 10°C. To this, 2-nitrobenzenesulfonyl chloride (1.3 eq) in acetone (1.0 vol) was added 30 min apart. The reaction mixture was maintained 5°C to 10°C for 1 h. After completion of reaction, water (4.0 vol) was added to the reaction mixture. The reaction mixture was concentrated and extracted with ethyl acetate (5.0-8.0 vol). The aqueous and organic layers were separated. The organic layer was concentrated, and hexane (3.0-6.0 vol) and maintained for 30 min. The reaction mixture was filtered and dried to get pale yellow solid compound of formula (V) (Yield: 90%, HPLC purity -94.88%).

Example-4.0: Preparation of compound of formula (VI)
In RBF, 33% w/w HBr in acetic acid (1.5-1.8 eq) were charged at RT. To this, compound of formula (V) (1.0 eq) was added in portions at temperature 15°C to 45°C and maintained for 4 to 5 h. After reaction completion, the reaction mass was cooled to 20°Cto 35°C. To the reaction mass, water (0.1 vol), toluene (5.0-8.0 vol) was added and maintained for 15 min. Further, pH of reaction mixture was maintained at to pH 4 to6. The aqueous and organic layers were separated. To the organic layer, DMF (0.4 vol) was added, and toluene was distilled out to obtain concentrated mass of compound of formula (VI) (without isolation, yield – 90%). To this concentrated mass, DMF (2.6 vol) was added, and the resulting mixture was proceeded for the next stage.

Example-5.0: Preparation of compound of formula (VII)
In RBF, reaction mixture (~ 17%) of compound formula (VI) was heated to 55°Cto 65°C. To this, sodium persulfate (1.8 eq) was added and maintained for 1 to 2 h. After reaction completion, the reaction mixture was cooled below 30°Cand aqueous methanol (3.0 vol) was added. The pH of reaction mixture was adjusted to pH 7 to 9 by adding 8.5% w/w aq. NaOH (4.5 eq.). The slurry was filtered, and wet cake was washed with aqueous methanol. The wet cake was added in water (4.0 vol) and maintained for 30 min. The slurry was filtered, the wet cake was washed with water and dried to obtain off-white solid of compound of formula (VII) (% yield – 85%).

Example-5.1: Preparation of compound of formula (VII)
In RBF, a compound of formula 1.56 Kg (IV, 1.0 eq), acetonitrile (9.0-12.0 vol) was added. To this a solution of phosphorous oxybromide (0.7-1.0 eq) in acetonitrile (1.0-1.4 vol) was added at 25°C to 30°C for 1 h. The reaction mixture was heated at 75°C to 80°C for 1 h. The completion of a reaction was monitored by HPLC. After reaction completion, the reaction mixture was cooled below 60°C to 65°C. The solvent was removed under vacuum. To the reaction mixture water (3.0-5.0 vol) was added and pH was maintained 7-8 using aq. sodium carbonate solution (20 % w/w). The crude compound was extracted with toluene (5.0-8.0 vol) and to this reaction solution DMF (0.4-0.6 vol.) was charged at 25°C to 30°C.The solvent was removed under vacuum and to this reaction mass DMF (2.0-4.0 vol.) was charged. The reaction mixture was heated at 55°C to 60°C. The solid sodium persulfate (1.8-2.2 eq) was added in lots and maintained temperature 55°C to 60°C for 2-4 h. The completion of reaction was checked by HPLC. After completion, aqueous methanol (3.0-5.0 vol) was added at 25°C to 30°C and pH was maintained in range 7-8 using aq. sodium hydroxide solution. The reaction mass was stirred for 1.0 h and slurry was filtered, and wet cake was washed with aqueous methanol (2.0-4.0 vol). To the wet cake water was added and reaction mass was heated at 30°C to 35°C and maintained for 1.0 h. The slurry was filtered, the wet cake was washed with water and dried to obtain off-white solid of compound of formula (VII) (Yield 80-86%, Assay >95%).

Example-5.3: Preparation of compound of formula (VII)
In RBF, a compound of formula (IV, 1.0 eq), acetonitrile (9.0 vol) was added. To this a solution of phosphorous oxybromide (0.7 eq) in acetonitrile (1.0 v) was added at 25°C to 30°C for 1 h. The reaction mixture was heated at 75°C to 80°C for 1 h. The completion of a reaction was monitored by HPLC. After reaction completion, the reaction mixture was cooled below 60°C to 65°C. The solvent was removed under vacuum. To the reaction mixture water was added and pH was maintained 7-8 using aq. sodium carbonate solution. The crude compound was extracted with toluene and to this reaction solution DMF (0.4 vol.) was charged at 25°C to 30°C.The solvent was removed under vacuum and to this reaction mass DMF (2.6 vol.) was charged. The reaction mixture was heated at 55°C to 60°C. The solid sodium persulfate (1.8 eq)was added in lots and maintained temperature 55°C to 60°C for 2-4 h. The completion of reaction was checked by HPLC. After completion, aqueous methanol was added at 25°C to 30°C and pH was maintained in range 7-8 using aq. sodium hydroxide solution. The reaction mass was stirred for 1.0 h and slurry was filtered, and wet cake was washed with aqueous methanol. To the wet cake water (4.0vol) was added and reaction mass was heated at 30°C to 35°C and maintained for 1.0 h. The slurry was filtered, the wet cake was washed with water and dried to obtain off-white solid of compound of formula (VII) (Yield –86%).

Example-6.0: Preparation of 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid of formula (I)
In RBF, compound of formula (VII, 1.0 eq), methanol (3-6 vol.) was charged at RT and maintained 20°C to 30°C for 15 min. To this, aqueous NaOH (1.3 eq) solution was added and maintained for 1 to 2 h. After reaction completion, aqueous sulfuric acid was added, and pH of slurry was maintained to pH 2.0-3.0.The slurry was filtered, the wet cake was washed with water and dried to obtain off-white solid of compound of formula (I)(Yield: 95%, Assay -99%).

Example-6.1: Preparation of 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid of formula (I)
In cylindrical reactor, compound of formula 1.42 Kg (VII, 1.0 eq), methanol (3-6 vol.) was charged at RT and maintained 20°C to 30°C for 15 min. To this, reaction mass added aqueous NaOH solution (1.3-1.5 eq) solution and maintained for 1 to 2 h. After reaction completion, aqueous sulfuric acid solution was added, and pH of slurry was maintained to pH 2.0-3.0. The slurry was filtered, the wet cake was washed with water (1.0-3.0 vol) and dried to obtain off-white solid of compound of formula (I) (Yield: 95-98%, Assay >99%).
,CLAIMS:We claim:

1. A process for the preparation of 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid of formula (I) comprising steps of:

a) reacting a compound of formula (IV) with 2-nitrobenzenesulfonyl chloride in presence of base in solvent to obtain a compound of formula (V);

b) reacting a compound of formula (V) with brominating agent in solvent to obtain a compound of formula (VI);

c) reacting a compound of formula (VI) with oxidizing agent in solvent to obtain a compound of formula (VII);

d) hydrolysing a compound of formula (VII) to obtain 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid of formula (I).

2. A process for preparation of 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid of formula (I) comprising steps of:

a) reacting a compound of formula (IV) with brominating agent, and oxidizing agent, in a solvent without isolation of compound formula (VI) to obtain a compound of formula (VII);

b) hydrolysing a compound of formula (VII) to obtain 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-carboxylic acid of formula (I).

3. The process as claimed in claim 1 and claim 2, wherein the compound formula (IV) is prepared by a process comprising steps of:

a) reacting 2,3-dichloropyridine (II) with hydrazine hydrate with or without base in solvent to obtain 3-chloro-2-hydrazino-pyridine (III), wherein base is selected from sodium carbonate, potassium carbonate, sodium bicarbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, potassium bicarbonate, triethylamine, diethylamine, N,N-diisopropylethylamine, 4-(dimethylamino) pyridine, ammonia, and pyridine;
b) reacting compound formula (III) with dialkyl maleate, alkali metal alkoxide, in presence of an acid and solvent.

4. A compound of formula (V)

5. The process as claimed in claim 1, wherein base is selected from sodium carbonate, potassium carbonate, sodium bicarbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, potassium bicarbonate,triethylamine, diethylamine, N,N-diisopropylethylamine, 4-(dimethylamino) pyridine, ammonia, and pyridine.

6. The process as claimed in claim 1 and claim 2, wherein said brominating agent is selected from hydrogen bromide, hydrogen bromide in acetic acid, bromine, N-bromosuccinimide, phosphorus oxybromide; and said oxidizing agent is selected from sodium persulfate, potassium persulfate, sodium perborate, hydrogen peroxide, organic peroxides, ammonium persulfate, potassium monopersulfate, and potassium permanganate.

7. The process as claimed in claim 3, wherein said dialkyl maleate is selected from dimethyl maleate, diethyl maleate, dipropyl maleate, dibutyl maleate; and said metal alkoxide is selected from sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium tert-butoxide, potassium methoxide, potassium ethoxide, and lithium tert-butoxide.

8. The process as claimed in claim 3, wherein said acid is selected from formic acid, acetic acid, hydrochloric acid, sulfuric acid, and phosphoric acid.

9. The process as claimed in claim 1, wherein solvent used for preparation compound (III), (IV), (V), (VI), and (I) is selected from water; alcoholic solvents such as methanol, ethanol, propanol, isopropanol, n-butanol; ketonic solvents such as acetone, methyl isobutyl ketone, ethyl methyl ketone and n-butanone; ether solvents such as diethyl ether, diisopropyl ether, methyl-t-butyl ether, methoxybenzene; ester solvents such as ethyl acetate, n- propyl acetate, n-butyl acetate; hydrocarbons such as hexane, heptane, toluene, xylene, cyclohexane; dichloromethane (DCM), ethylene dichloride, tetrahydrofuran (THF), acetonitrile, propionitrile, methylene bromide; and for preparation of compound formula (VII) is selected from polar aprotic solvent such as acetonitrile, propionitrile, dimethylformamide (DMF), dimethylsulphoxide (DMSO).