DESC:Improved Process of Preparation of Carboxamide derivatives

Field of the Invention
The present invention relates to an improved process of preparation of Carboxamide derivatives. More particularly, the present invention relates to an improved process of preparation of Chlorantraniliprole of Formula I.

Background of the Invention
Chlorantraniliprole (5-bromo-N-[4-chloro-2-methyl-6-(methylcarbamoyl)phenyl]-2-(3-chloropyridin-2-yl)pyrazole-3-carboxamide) of Formula I is an insecticide belonging to the anthranilic diamide class of chemistry and is intended for the control of Lepidopteran, Coleopteran, and some Dipteran pests in commercial agriculture on both perennial and annual crops.

Formula I

A number of processes for the preparation of chlorantraniliprole are already known from the literature. US patent no. 7,528,260B2 provides a process a preparation of chlorantraniliprole by using a mixture of 3-bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylic acid and 2-amino-5-chloro-N,3-dimethylbenzamide in a solvent with an organic base, followed by the addition of methanesulfonyl chloride. The patent discloses the use of organic bases such as pyridine, 3-picoline and 4-picoline.

The above process has disadvantages as it involves the use of organic base like pyridine, picoline etc., which are hazardous to environment, as high volume of aqueous and organic waste are generated during the process. Also, the process uses reagent such as methanesulfonyl chloride which is not only expensive but also hazardous to environment. Further, the process is carried out at low temperature which makes the process commercially expensive. The patent also fails to disclose the purity and the yield of the final product obtained after purification.

PCT publication No. WO/2019/207595, discloses a process of preparation of chlorantraniliprole reacting 3-bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylic acid, with thionyl chloride in a solvent selected from acetonitrile, toluene or mixture thereof, to obtain 3-Bromo-l-(3-chloro- 2-pyridinyl)-1 H-pyrazole-5-carboxylic acid chloride. Thereafter, reacting 3-Bromo-l-(3-chloro- 2-pyridinyl)-1 H-pyrazole-5-carboxylic acid chloride in situ with 2-amino-5-chloro-3,N-dimethylbenzamide, in the presence of pyridine or picoline in solvent acetonitrile, toluene or mixture thereof to obtain crude chlorantraniliprole. The crude product was then purified in solvent to obtain the pure chlorantraniliprole. The above process has disadvantages as it involves the use of organic base like pyridine, 3-picoline which are hazardous to environment, as high volume of aqueous and organic waste are generated during the process.

US patent 8,217,179B2 provides a process by reacting 3-bromo-1-(3-chloro-2-pyridinyl)-4,5-dihydro-1H-pyrazole-5-carboxylic acid, with thionyl chloride in a solvent, to obtain 3-bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carbonyl chloride. Thereafter, 2-amino-5-chloro-N,3-dimethylbenzamide in acetonitrile is reacted with 3-bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carbonyl chloride without the presence of acid binding agent to obtain chlorantraniliprole.
The patent discloses the use of hazardous reagent like thionyl chloride in excess of 5 mole equivalent which generates huge quantity of HCl gas which is harmful to environment. Also excess thionyl chloride has to be distilled off which is an undesired operation.
PCT publication no. WO/2021/099978 provides a process wherein 3-bromo-1-(3-chloro-2-pyridinyl)-lH-pyrazole-5-carboxylic acid was added to solvent, in the presence of inorganic base to form a slurry. Thereafter, slurry was reacted with 2-amino-5-chloro-N,3-dimethylbenzamide followed by adding sulfonyl chloride to obtain Chlorantraniliprole.
The disadvantages of the above process are usage of expensive reagents such as sulfonyl chlorides selected from methanesulfonyl chloride, p-methyl-benzenesulfonyl chloride, p-chlorobenezenesulfonyl chloride, m-nitrobenezenesulfonyl chloride. Also high volume of aqueous effluent is generated during the process. Further, the yield of the product is also low.
Hence, there is a need in the art to provide an improved process of preparation of Chlorantraniliprole which is simple, cost-effective, reduces effluent load and results in product with high purity and good yield on a commercial scale.

Summary of the Invention
Accordingly, the present invention provides an improved process of preparation of Chlorantraniliprole of Formula I,

Formula I
said process comprising the steps of:
a) reacting 3-bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylic acid, with a
chlorinating agent in a suitable solvent to obtain 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride,
b) reacting the 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride with 2-amino-5-chloro-N, 3-dimethylbenzamide, in presence of an inorganic base in a suitable solvent to obtain Chlorantraniliprole of Formula-I,
c) isolating the Chlorantraniliprole of formula-I.

Detailed description of the Invention
The present invention provides an improved process of preparation of Chlorantraniliprole of Formula I.

Formula I
said process comprising the steps of:
a) reacting 3-bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylic acid, with a
chlorinating agent in a suitable solvent to obtain 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride,
b) reacting the 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride with 2-amino-5-chloro-N, 3-dimethylbenzamide, in presence of an inorganic base in a suitable solvent to obtain Chlorantraniliprole of Formula-I,
c) isolating the Chlorantraniliprole of formula-I.

In an embodiment, 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride may be isolated in step a). In an alternative embodiment, step a) and step b) are carried out in situ.

In another embodiment, the chlorinating agent used in step a) is selected from thionyl Chloride, Oxalyl chloride, Cyanuric Chloride, Phosphorus oxychloride, Phosphorus trichloride, Phosphorus pentachloride, etc.

In another embodiment, in step a) optionally the reaction is carried out in the presence of catalytic amount of Dimethylformamide (DMF).

In an embodiment, the suitable solvent used in step a) is selected from toluene, acetonitrile, methylene chloride, chloroform, xylene, methyl ethyl ketone, benzene, dioxane, hexane, carbon tetrachloride, tetrahydrofuran, dichloromethane, bromodichloromethane, dibromochloromethane, trichlorofluoromethane, 1,1-dichloroethane, 1,2- dichloroethane, 1,1,1-trichloroethane, 1,12-trichloroethane, 1,1,2,2- tetrachloroethane, 1,1-dichloroethylene, cis-1,2-dichloroethylene, trans-1,2- dichloroethylene, trichloroethylene or mixture thereof; hydrocarbon solvents such as cyclohexane, heptane or mixture thereof.

In an embodiment, the mole equivalents of chlorinating reagent used in step a) are 1.0 to 2.0, preferably 1.2 to 1.5 and more preferably 1.0 to 1.4 mole equivalents with respect to 3-bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylic acid.

In an embodiment, in step (a), the reaction may be performed from 25°C to 125°C for 1 hour to 12 hours, preferably 60-90°C for 1 hour to 5 hours. The obtained 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride may be used in the next reaction directly without isolation.

In an embodiment, in step b) 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride reacts with 2-amino-5-chloro-N, 3-dimethylbenzamide, in presence of an inorganic base in a suitable solvent to obtain Chlorantraniliprole of Formula-I.

In an embodiment, the inorganic base used in step b) is selected from sodium carbonate, potassium carbonate, lithium carbonate, magnesium carbonate, cesium carbonate, calcium carbonate sodium bicarbonate, potassium bicarbonate, potassium hydroxide, sodium hydroxide, lithium hydroxide, magnesium hydroxide, calcium hydroxide, dipotassium phosphate, tripotassium phosphate, disodium phosphate, trisodium phosphate or mixtures thereof, preferably sodium bicarbonate, potassium bicarbonate, sodium carbonate and potassium carbonate.

In an embodiment, the suitable solvent used in step b) is organic solvents, for example polar aprotic solvent comprises acetonitrile, dimethylformamide, tetrahydrofuran, ethyl acetate, acetone, dimethylsulfoxide or mixture thereof. The chlorinating solvent comprises dichloromethane, chloroform, bromodichloromethane, dibromochloromethane, trichlorofluoromethane, carbon tetrachloride, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,1,2,2-tetrachloroethane, 1,1-dichloroethylene, cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, trichloethylene or mixture thereof. Hydrocarbon solvents such as cyclohexane, hexane, heptane, toluene, xylene or mixture thereof.

In an embodiment, the mole equivalents of 2-amino-5-chloro-N, 3-dimethylbenzamide used in step b) are 0.9 to 1.2 with respect to 3-bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylic acid.

In a preferred embodiment, the solvent used in step b) is selected from acetonitrile or a mixture of acetonitrile-water or a toluene or a mixture of toluene-water. The ratio of acetonitrile-water or toluene-water is 15:1, preferably is in the range of 3:1 and more preferably is in the range of 1:1.

In an embodiment, the mole equivalents of inorganic base used in step b) are 0.4 to 2.5, preferably 1.4 to 2 mole equivalents with respect to 3-bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylic acid.

In an embodiment, in step b), the reaction may be performed from 0°C to 60°C for a time period in the range of 1 hour to 60 hours, preferably 0 to 25°C for 2 hours to 5 hours.

In an embodiment, in step c) Chlorantraniliprole of formula-I is isolated by filtration at a temperature in the range of 0-70oC.

In an embodiment, in step c) filtered Chlorantraniliprole of formula-I is washed with solvents selected from water, polar aprotic solvent comprises acetonitrile, dimethylformamide, tetrahydrofuran, ethyl acetate, acetone, dimethylsulfoxide or mixture thereof; Hydrocarbon solvents such as cyclohexane, hexane, heptane, toluene, xylene or mixture thereof; or combination or mixtures of solvents, optionally the solvents are used at ambient to at a temperature in the range of 20-70oC.

In an embodiment, in step c) the Chlorantraniliprole of formula-I dried at a temperature in the range of 25-100oC.

The process according to the present invention has the following advantages over the known prior art:
• The inorganic base used in the present invention is cost efficient, economical and environment friendly.
• The inorganic base used in the present invention can be separated out easily.
• The process of the present invention is carried out at ambient temperature.
• The process is simple, efficient and environment friendly.
• The process provides chlorantraniliprole with high purity and yield.
• The process of the present invention requires the minimum operations which is economical and efficient on commercial scale.
• Process is carried out in presence of an inorganic base in a selected solvent thus significantly reduces the effluent load.

The following examples are provided to illustrate the invention and are merely for illustrative purpose only and should not be construed to limit the scope of the invention.

Example-01: Preparation of Chlorantraniliprole of formula-I.
3-bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylic acid (20gm, 0.066mole) was added to acetonitrile (100ml), under stirring to form a reaction mass. Thionyl chloride (10.56gm, 0.088mole) and DMF in catalytic amount was added to the reaction mass and stirred at 70-75°C and monitor the reaction progress. In another flask 2-amino-5-chloro-N, 3-dimethylbenzamide (12.7gm, 0.064 mole), potassium carbonate (17.5gm, 0.126 mole) and acetonitrile (40ml) and water (40ml) were added. Slowly 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride was added while maintaining the temperature at 0-10°C to a reaction mixture. This reaction mixture was stirred at 0-10°C for 2 hrs after completion of addition; monitor the reaction by HPLC for the formation of chlorantraniliprole. The obtained chlorantraniliprole was filtered and washed with water (40ml) followed by acetonitrile (40ml). The resulting chlorantraniliprole was dried to afford chlorantraniliprole of > 96% Purity (by HPLC) with > 83% Yield.

Example-02: Preparation of Chlorantraniliprole of formula-I.
3-bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylic acid (20gm, 0.066mole) was added to acetonitrile (100ml), under stirring to form a reaction mass. Thionyl chloride (11.3gm, 0.095mole) and DMF in catalytic amount was added to the reaction mass and stirred at 70-75°C and monitor the reaction progress. In another flask 2-amino-5-chloro-N, 3-dimethylbenzamide (14g, 0.07mole), sodium carbonate (13.5gm, 0.127mole) and acetonitrile (28ml), water (2ml) were added. Slowly 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride was added while maintaining the temperature at 0-10°C to a reaction mixture. This reaction mixture was stirred at 10-15°C for 2 hrs after completion of addition; monitor the reaction by HPLC for the formation of chlorantraniliprole. The obtained chlorantraniliprole was filtered and washed with water (80ml) followed by acetonitrile (60ml). The resulting chlorantraniliprole was dried to afford chlorantraniliprole of > 93% Purity (by HPLC) with > 81% Yield.

Example-03: Preparation of Chlorantraniliprole of formula-I.
3-bromo-l-(3-chloro-2-pyridinyl)-lH-pyrazole-5-carboxylic acid (20gm, 0.066mole) was added to acetonitrile (100ml), under stirring to form a reaction mass. Thionyl chloride (11.8gm, 0.099mole) and DMF in catalytic amount was added to the reaction mass and stirred at 70-75°C and monitor the reaction progress. In another flask 2-amino-5-chloro-N, 3-dimethylbenzamide (13.1gm, 0.066mole), sodium bicarbonate (11.1gm, 0.132mole) and acetonitrile (40ml) and water (40ml) were added. Slowly 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride was added while maintaining the temperature at 0-10°C to a reaction mixture. This reaction mixture was stirred at 0-10°C for 2 hrs after completion of addition; monitor the reaction by HPLC for the formation of chlorantraniliprole. The obtained chlorantraniliprole was filtered and washed with water (40ml) followed by acetonitrile (40ml). The resulting chlorantraniliprole was dried to afford chlorantraniliprole of > 97.5% Purity (by HPLC) with > 84% Yield.

Example-04: Preparation of Chlorantraniliprole of formula-I.
3-bromo-l-(3-chloro-2-pyridinyl)-lH-pyrazole-5-carboxylic acid (20gm, 0.066mole) was added to acetonitrile (100ml), under stirring to form a reaction mass. Thionyl chloride (11.0gm, 0.092mole) was added to the reaction mass and stirred at 70-75°C and monitor the reaction progress. In another flask 2-amino-5-chloro-N,3-dimethylbenzamide (13.1gm, 0.066mole), sodium bicarbonate (11.1gm, 0.132mole) and acetonitrile (40ml) and water (40ml) were added. Slowly 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride was added while maintaining the temperature at 0-10°C to a reaction mixture. This reaction mixture was stirred at 0-10°C for 2hrs after completion of addition; monitor the reaction for the formation of chlorantraniliprole. The obtained chlorantraniliprole was filtered and washed with water (40ml) followed by acetonitrile (20ml). The resulting chlorantraniliprole was dried to afford chlorantraniliprole of > 97.5% Purity (by HPLC) with > 84% Yield.

Example-05: Preparation of Chlorantraniliprole of formula-I.
3-bromo-l-(3-chloro-2-pyridinyl)-lH-pyrazole-5-carboxylic acid (20gm, 0.066mole) was added to Toluene (100ml) under stirring to form a reaction mass. Thionyl chloride (11.1gm, 0.093mole) and DMF in catalytic amount was added to the reaction mass and stirred at 70-75°C, monitor the reaction progress. In another flask 2-amino-5-chloro-N, 3-dimethylbenzamide (12.8gm, 0.064mole), potassium carbonate (18.3gm, 0.132mole), toluene (40ml) and water (40ml) were added. Slowly 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride was added while maintaining the temperature at 0-5°C to a reaction mixture. This reaction mixture was stirred at 0-10°C for 2 hrs after completion of addition and monitor by HPLC for the formation of chlorantraniliprole. The obtained chlorantraniliprole was filtered and washed with water (40ml) followed by Acetonitrile (40ml). The resulting chlorantraniliprole was dried to afford chlorantraniliprole of >97% Purity (by HPLC) with >83% Yield.

Example-06: Preparation of Chlorantraniliprole of formula-I.
3-bromo-l-(3-chloro-2-pyridinyl)-lH-pyrazole-5-carboxylic acid (20gm, 0.066mole) was added to Toluene (100ml) under stirring to form a reaction mass. Thionyl chloride (10.5gm, 0.088mole) and DMF in catalytic amount was added to the reaction mass and stirred at 70-75°C, monitor the reaction progress. In another flask 2-amino-5-chloro-N, 3-dimethylbenzamide (12.7gm, 0.063mole), sodium carbonate (13.4gm, 0.126mole), toluene (40ml) and water (40ml) were added. Slowly 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride was added while maintaining the temperature at 0-10°C to a reaction mixture. This reaction mixture was stirred at 0-10°C for 3 hrs after completion of addition and monitor by HPLC for the formation of chlorantraniliprole. The obtained chlorantraniliprole was filtered and washed with water (40ml) followed by Toluene (40ml). The resulting chlorantraniliprole was dried to afford chlorantraniliprole of > 97% Purity (by HPLC) with > 82% Yield.

Example-07: Preparation of Chlorantraniliprole of formula-I.
3-bromo-l-(3-chloro-2-pyridinyl)-lH-pyrazole-5-carboxylic acid (20gm, 0.066mole) was added to Toluene (100ml) ) under stirring to form a reaction mass. Thionyl chloride (11.0gm, 0.092mole) and DMF in catalytic amount was added to the reaction mass and stirred at 70-75°C, monitor the reaction progress. In another flask 2-amino-5-chloro-N, 3-dimethylbenzamide (12.8gm, 0.064mole), sodium bicarbonate (11.1gm, 0.132mole), toluene (40ml) and water (40ml) were added. Slowly 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride was added while maintaining the temperature at 0-5°C to a reaction mixture. This reaction mixture was stirred at 0-5°C for 2 hrs after completion of addition and monitor by HPLC for the formation of chlorantraniliprole. The obtained chlorantraniliprole was filtered and washed with water (40ml) followed by Toluene (40ml). The resulting chlorantraniliprole was dried to afford chlorantraniliprole of > 95% Purity (by HPLC) with > 75% Yield.

Example-08: Preparation of Chlorantraniliprole of formula-I.
3-bromo-l-(3-chloro-2-pyridinyl)-lH-pyrazole-5-carboxylic acid (20gm, 0.066mole) was added to Toluene (100ml) under stirring to form a reaction mass. Thionyl chloride (11.0gm, 0.092mole) was added to the reaction mass and stirred at 70-75°C, monitor the reaction progress. In another flask 2-amino-5-chloro-N,3-dimethylbenzamide (13.1gm, 0.066mole), sodium bicarbonate (11.1gm, 0.132mole), toluene (40ml) and water (40ml) were added. Slowly 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride was added while maintaining the temperature at 0-10°C to a reaction mixture. This reaction mixture was stirred at 0-10°C for 2hrs after completion of addition and monitor the reaction for the formation of chlorantraniliprole. The obtained chlorantraniliprole was filtered and washed with water (40ml) followed by Toluene (40ml). The resulting chlorantraniliprole was dried to afford chlorantraniliprole of > 95% Purity (by HPLC) with > 75% Yield.

Example-09: Preparation of Chlorantraniliprole of formula-I.
3-bromo-l-(3-chloro-2-pyridinyl)-lH-pyrazole-5-carboxylic acid (100gm, 0.33mole) was added to Toluene (500ml) under stirring to form a reaction mass. Thionyl chloride (55.1gm, 0.462mole) was added to the reaction mass and stirred at 70-75°C, monitor the reaction progress. In another flask 2-amino-5-chloro-N, 3-dimethylbenzamide (65.66gm, 0.33mole), sodium bicarbonate (55.5gm, 0.66mole), Acetonitrile (200ml) and water (200ml) were added. Slowly 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride was added while maintaining the temperature at 0-10°C to a reaction mixture. This reaction mixture was stirred at 0-10°C for 2 hrs after completion of addition and monitor by HPLC for the formation of chlorantraniliprole. Heat the reaction mass to 40-50°C and obtained chlorantraniliprole was filtered and washed with water (200ml) followed by Acetonitrile (100ml). The resulting chlorantraniliprole was dried to afford chlorantraniliprole of > 99% Purity (by HPLC) with >92% Yield. The obtained product is characterized by 1H NMR: (400 MHz, DMSO) d 2.16 (3H) (s), d 2.65 – 2.66 (3H) (d), 7.34 – 7.39 (2H) (d), d 7.471-7.476 (1H) (d), d 7.59 – 7.62 (1H) (q), d 8.15 – 8.16 (1H) (d), d 8.17 – 8.18 (1H) (d), d 8.49 – 8.50 (1H) (d), d 10.27 (1H) (s).

Example-10: Preparation of Chlorantraniliprole of formula-I.
3-bromo-l-(3-chloro-2-pyridinyl)-lH-pyrazole-5-carboxylic acid (100gm, 0.33mole) was added to Toluene (500ml) under stirring to form a reaction mass. Thionyl chloride (55.1gm, 0.462mole) and DMF in catalytic amount was added to the reaction mass and stirred at 70-75°C, monitor the reaction progress. In another flask 2-amino-5-chloro-N, 3-dimethylbenzamide (65.66gm, 0.33mole), sodium bicarbonate (55.5gm, 0.66mole), Acetonitrile (200ml) and water (200ml) were added. Slowly 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride was added while maintaining the temperature at 0-10°C to a reaction mixture. This reaction mixture was stirred at 0-10°C for 2hrs after completion of addition and monitor by HPLC for the formation of chlorantraniliprole. Heat the reaction to 40-50°C and obtained chlorantraniliprole was filtered and washed with water (200ml) followed by Acetonitrile (100ml). The resulting chlorantraniliprole was dried to afford chlorantraniliprole of > 99% Purity (by HPLC) with >92% Yield.

Example-11: Preparation of Chlorantraniliprole of formula-I.
3-bromo-l-(3-chloro-2-pyridinyl)-lH-pyrazole-5-carboxylic acid (20gm, 0.066mole) was added to Toluene (100ml) under stirring to form a reaction mass. Thionyl chloride (11.1gm, 0.0923mole) and DMF in catalytic amount was added to the reaction mass and stirred at 70-75°C, monitor the reaction progress. In another flask 2-amino-5-chloro-N, 3-dimethylbenzamide (13.1gm, 0.066mole), sodium carbonate (14gm, 0.132mole), Acetonitrile (40ml) and water (40ml) were added. Slowly 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride was added while maintaining the temperature at 0-5°C to a reaction mixture. This reaction mixture was stirred at 0-10°C for 2 hrs after completion of addition and monitor by HPLC for the formation of chlorantraniliprole. The obtained chlorantraniliprole was filtered and washed with water (40ml) followed by Acetonitrile (40ml). The resulting chlorantraniliprole was dried to afford chlorantraniliprole of > 98% Purity (by HPLC) with > 80% Yield.

Example-12: Preparation of Chlorantraniliprole of formula-I.
3-bromo-l-(3-chloro-2-pyridinyl)-lH-pyrazole-5-carboxylic acid (20gm, 0.066mole) was added to Toluene (100ml) under stirring to form a reaction mass. Thionyl chloride (11.1gm, 0.093mole) and DMF in catalytic amount was added to the reaction mass and stirred at 70-75°C, monitor the reaction progress. In another flask 2-amino-5-chloro-N, 3-dimethylbenzamide (13.1gm, 0.066mole), potassium carbonate (17.5gm, 0.126mole), Acetonitrile (40ml) and water (40ml) were added. Slowly 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride was added while maintaining the temperature at 0-5°C to a reaction mixture. This reaction mixture was stirred at 0-10°C for 2 hrs after completion of addition and monitor by HPLC for the formation of chlorantraniliprole. The obtained chlorantraniliprole was filtered and washed with water (40ml) followed by Acetonitrile (40ml). The resulting chlorantraniliprole was dried to afford chlorantraniliprole of >96% Purity (by HPLC) with >87% Yield.

Example-13: Preparation of Chlorantraniliprole of formula-I.
3-bromo-l-(3-chloro-2-pyridinyl)-l H-pyrazole-5-carboxylic acid (20gm, 0.066mole) was added to Acetonitrile (100ml) under stirring to form a reaction mass. Thionyl chloride (11.1gm, 0.093mole) and DMF in catalytic amount was added to the reaction mass and stirred at 70-75°C, monitor the reaction progress. In another flask 2-amino-5-chloro-N, 3-dimethylbenzamide (13.1gm, 0.066mole), Sodium hydroxide (5.4gm, 0.132mole), Acetonitrile (40ml) and water (40ml) were added. Slowly 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride was added while maintaining the temperature at 0-5°C to a reaction mixture. This reaction mixture was stirred at 0-10°C for 2 hrs after completion of addition and monitor by HPLC for the formation of chlorantraniliprole. The obtained chlorantraniliprole was filtered and washed with water (40ml) followed by Acetonitrile (40ml). The resulting chlorantraniliprole was dried to afford chlorantraniliprole of >94% Purity (by HPLC) with >66% Yield.

Example-14: Preparation of Chlorantraniliprole of formula-I.
3-bromo-l-(3-chloro-2-pyridinyl)-lH-pyrazole-5-carboxylic acid (20gm, 0.066mole) was added to Acetonitrile (100ml) under stirring to form a reaction mass. Thionyl chloride (11.1gm, 0.093mole) and DMF in catalytic amount was added to the reaction mass and stirred at 70-75°C, monitor the reaction progress. In another flask 2-amino-5-chloro-N, 3-dimethylbenzamide (13.1gm, 0.066mole), potassium hydroxide (8.6gm, 0.13mole), Acetonitrile (40ml) and water (40ml) were added. Slowly 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride was added while maintaining the temperature at 0-5°C to a reaction mixture. This reaction mixture was stirred at 0-10°C for 2 hrs after completion of addition and monitor by HPLC for the formation of chlorantraniliprole. The obtained chlorantraniliprole was filtered and washed with water (40ml) followed by Acetonitrile (40ml). The resulting chlorantraniliprole was dried to afford chlorantraniliprole of >95% Purity (by HPLC) with >53% Yield.

Example-15: Preparation of Chlorantraniliprole of formula-I.
3-bromo-l-(3-chloro-2-pyridinyl)-lH-pyrazole-5-carboxylic acid (20gm, 0.066mole) was added to Toluene (100ml) under stirring to form a reaction mass. Thionyl chloride (11.1gm, 0.093mole) was added to the reaction mass and stirred at 70-75°C, monitor the reaction progress. In another flask 2-amino-5-chloro-N,3-dimethylbenzamide (13.1gm, 0.066mole), potassium carbonate (17.5gm, 0.126mole), Acetonitrile (40ml) and water (40ml) were added. Slowly 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride was added while maintaining the temperature at 0-10°C to a reaction mixture. This reaction mixture was stirred at 0-10°C for 2hrs after completion of addition and monitor the reaction for the formation of chlorantraniliprole. The obtained chlorantraniliprole was filtered and washed with water (40ml) followed by Acetonitrile (40ml). Dry the material to obtained chlorantraniliprole of >96% Purity with >87% Yield.

Example-16: Preparation of Chlorantraniliprole of formula-I.
3-bromo-l-(3-chloro-2-pyridinyl)-lH-pyrazole-5-carboxylic acid (20gm, 0.066mole) was added to Toluene (100ml) under stirring to form a reaction mass. Phosphorus oxychloride (14.6g, 0.092mole) and DMF in catalytic amount was added to the reaction mass and stirred at 70-75°C, monitor the reaction progress. In another flask 2-amino-5-chloro-N, 3-dimethylbenzamide (13.1gm, 0.066mole), sodium bicarbonate (11g, 0.13mole), Acetonitrile (40ml) and water (40ml) were added. Slowly 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride was added while maintaining the temperature at 0-10°C to a reaction mixture. This reaction mixture was stirred at 0-10°C for 2 hrs after completion of addition and monitor by HPLC for the formation of chlorantraniliprole. Heat the reaction mass to 40-50°C and filtered the product, washed with water (40ml) followed by Acetonitrile (20ml). The resulting chlorantraniliprole was dried to afford chlorantraniliprole of >98% Purity (by HPLC) with >84% Yield.

From the foregoing it will be observed that numerous modifications and variations can be effectuated without departing from the true spirit and scope of the novel concepts of the present invention. It is to be understood that no limitations with respect to the specific embodiments illustrated is intended or should be inferred. It should be understood that all such modifications and improvements have been deleted herein for the sake of conciseness and readability but are properly within the scope of the following claims. ,CLAIMS:1. An improved process of preparation of Chlorantraniliprole of Formula I,

Formula I
said process comprising the steps of:
a) reacting 3-bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylic acid, with a chlorinating agent in a suitable solvent to obtain 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride;
b) reacting the 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carbonyl chloride with 2-amino-5-chloro-N, 3-dimethylbenzamide, in presence of an inorganic base in a suitable solvent to obtain Chlorantraniliprole of Formula-I; and
c) isolating the Chlorantraniliprole of formula-I.

2. The process as claimed in claim 1, wherein the chlorinating agent used in step a) is selected from thionyl chloride, Oxalyl chloride, Cyanuric chloride, Phosphorus oxychloride, Phosphorus trichloride, Phosphorus pentachloride.

3. The process as claimed in claim 1, wherein the suitable solvent used in step a) is selected from toluene, acetonitrile, methylene chloride, chloroform, xylene, methyl ethyl ketone, benzene, dioxane, hexane, carbon tetrachloride, tetrahydrofuran, dichloromethane, bromodichloromethane, dibromochloromethane, trichlorofluoromethane, 1,1-dichloroethane, 1,2- dichloroethane, 1,1,1-trichloroethane, 1,12-trichloroethane, 1,1,2,2- tetrachloroethane, 1,1-dichloroethylene, cis-1,2-dichloroethylene, trans-1,2- dichloroethylene, trichloroethylene; hydrocarbon solvents such as cyclohexane, heptane or mixture thereof.

4. The process as claimed in claim 1, wherein in step a) optionally the reaction is carried out in the presence of catalytic amount of Dimethylformamide (DMF).

5. The process as claimed in claim 1, wherein the mole equivalents of chlorinating reagent used in step a) are 1.0 to 2.0, preferably 1.2 to 1.5 and more preferably 1.0 to 1.4 mole equivalents with respect to 3-bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylic acid.

6. The process as claimed in claim 1, wherein in step (a) the reaction is performed from 25°C to 125°C for 1 hour to 12 hours, preferably 60-90°C for 1 hour to 5 hours.

7. The process as claimed in claim 1, wherein the inorganic base used in step b) is selected from sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, potassium hydroxide, sodium hydroxide, lithium hydroxide, lithium carbonate, magnesium carbonate, magnesium hydroxide, cesium carbonate, calcium carbonate, calcium hydroxide or mixtures thereof, preferably sodium bicarbonate, potassium bicarbonate, sodium carbonate and potassium carbonate.

8. The process as claimed in claim 1, wherein the suitable solvent used in step b) is organic solvents is selected from polar aprotic solvents acetonitrile, dimethylformamide, tetrahydrofuran, ethyl acetate, acetone, dimethylsulfoxide or mixture thereof; the chlorinating solvents dichloromethane, chloroform, bromodichloromethane, dibromochloromethane, trichlorofluoromethane, carbon tetrachloride, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,1,2,2-tetrachloroethane, 1,1-dichloroethylene, cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, trichloroethylene or mixture thereof; hydrocarbon solvents cyclohexane, hexane, heptane, toluene, xylene or mixture thereof.

9. The process as claimed in claim 1, wherein the mole equivalents of 2-amino-5-chloro-N, 3-dimethylbenzamide used in step b) are 0.9 to 1.2 with respect to 3-bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylic acid.

10. The process as claimed in claim 1, wherein the solvent used in step b) is selected from acetonitrile or a mixture of acetonitrile-water or a toluene or a mixture of toluene-water wherein ratio of acetonitrile: water or toluene: water is 15:1, preferably is in the range of 3:1 and more preferably is in the range of 1:1.

11. The process as claimed in claim 1, wherein the mole equivalents of inorganic base used in step b) are 0.4 to 2.5, preferably 1.4 to 2 mole equivalents with respect to 3-bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylic acid.

12. The process as claimed in claim 1, wherein in the step b) the reaction is performed from 0°C to 60°C for a time period in the range of 1 hour to 60 hours, preferably 0 to 25°C for 2 hours to 5 hours.

13. The process as claimed in claim 1, wherein in step c) Chlorantraniliprole of formula-I is isolated by filtration at a temperature in the range of 0-70oC.

14. The process as claimed in claim 1, wherein in step c) filtered Chlorantraniliprole of formula-I is washed with solvents selected from water; polar aprotic solvent acetonitrile, dimethylformamide, tetrahydrofuran, ethyl acetate, acetone, dimethylsulfoxide or mixture thereof; hydrocarbon solvents cyclohexane, hexane, heptane, toluene, xylene or mixture thereof; or combination or mixtures of solvents, optionally the solvents are used at a temperature in the range of 20-70oC.