WO2024176261A1

WO2024176261A1 - A process for preparation of anthranilamide compound and intermediate thereof

Info

Publication number: WO2024176261A1
Application number: PCT/IN2024/050188
Authority: WO
Inventors: Jigar Kantilal DESAI; Digish Manubhai PANCHAL
Original assignee: Upl Limited
Priority date: 2023-02-21
Filing date: 2024-02-21
Publication date: 2024-08-29
Also published as: AR131889A1

Abstract

The present invention relates to a process for preparation of an anthranilamide compound, more particularly cyantraniliprole. The present invention relates to a process for preparation of cyantraniliprole (I) free of impurities comprising treatment of crude cyantraniliprole with a solvent.

Description

A PROCESS FOR PREPARATION OF ANTHRANILAMIDE COMPOUND AND INTERMEDIATE THEREOF FIELD OF THE INVENTION: The present invention relates to a process for preparation of an anthranilamide compound or its salt thereof. More particularly, the present invention relates to a process for preparation of cyantraniliprole and intermediate thereof. BACKGROUND OF THE INVENTION: Anthranilamides are a new class of compounds with extremely potent insecticidal activity. These nitrogen-containing aromatic compounds selectively act on targeted ryanodine receptors which form calcium ion channels, responsible for muscle function in insects. One such insecticidal anthranilamide is cyantraniliprole, chemically known as 3-bromo-1-(3-chloropyridin-2-yl)-N-[4-cyano-2-methyl-6- (methylcarbamoyl) phenyl]-1H-pyrazole-5-carboxamide, and structurally represented as formula (I):

Cyantraniliprole was first disclosed in PCT publication number WO2004067528. The process for preparation of cyantraniliprole is also known in prior art. Additionally, another U.S. patent 8410278 discloses that cyantraniliprole exists in two polymorphic forms namely, Polymorph A and Polymorph B. It has been disclosed in said patent that the water content of Polymorph B changes significantly on exposure to variations in atmospheric humidity, whereas Polymorph A does not gain or lose appreciable amounts of water when subjected to variations in atmospheric humidity. Therefore, it is known that cyantraniliprole has tendency to absorb moisture. Such undesired absorption of moisture from atmosphere impacts chemical purity of the active ingredient and is considered as impurity. The inventors of the present invention have developed a process for obtaining cyantraniliprole, free of impurities including water, which is suitable for making end products for the intended use. Furthermore, as cyantraniliprole is an important insecticide, the intermediates formed in the process for preparation of cyantraniliprole are also of importance. It is well known that the purity of end product largely depends on the purity of intermediate. The present invention also provides highly pure intermediates having formula (II) which directly impacts the purity of final product, i.e., cyantraniliprole, and the process for preparation of the same. OBJECTIVES OF THE INVENTION: It is a primary objective of the present invention to provide a process for preparation of cyantraniliprole having formula (I), which is free of impurities. It is another objective of the present invention to provide a process for preparation of cyantraniliprole (I) ), which is free of impurities. It is another objective of the present invention to provide a highly pure intermediate compound having formula (II), which is useful for preparation of cyantraniliprole. It is another objective of the present invention to provide a crystalline intermediate having formula (II). It is yet another objective of the present invention to provide a process for preparation of a crystalline intermediate having formula (II). SUMMARY OF THE INVENTION: In an aspect of the present invention, there is provided a process for preparation of an anthranilamide compound or its salt thereof. In another aspect of the present invention, there is provided a process for preparation of cyantraniliprole (I), which is free of impurities:

the process comprising the steps: a) reacting a compound of formula (III) with a compound of formula (IV) in presence of a solvent to obtain a compound of formula (II);

Formula (III) Formula (IV) Formula (II) b) reacting the compound of formula (II) with methyl amine to obtain crude cyantraniliprole; and c) treating the crude cyantraniliprole with at least one solvent having a dielectric constant of less than 6 and isolating obtained cyantraniliprole having formula (I), which is free of impurities. In an aspect of the present invention, there is provided cyantraniliprole (I) comprising purity more than 95% and comprising less than 1% water. In an aspect of the present invention, there is provided a crystalline intermediate of formula (II) characterized by a X-ray powder diffraction pattern. BRIEF DESCRIPTION OF THE DRAWINGS: Figure 1 illustrates powder X-ray diffraction (PXRD) pattern of cyantraniliprole (I), which is free of impurities prepared according to the present invention. Figure 2 illustrates powder X-ray diffraction (PXRD) pattern of crystalline compound of formula (II) prepared according to present invention. Figure 3 illustrates differential scanning calorimetric (DSC) thermogram of crystalline compound of formula (II) prepared according to present invention. Figure 4 illustrates Fourier transform infrared (FTIR) spectroscopy of crystalline compound of formula (II) prepared according to present invention. DETAILED DESCRIPTION OF THE INVENTION: Those skilled in art will be aware that invention described herein is subject to variations and modifications other than those specifically described. It is to be understood that the invention described herein includes all such variations and modifications. The invention also includes all such steps, features, compositions and methods referred to or indicated in this specification, individually or collectively, and any and all combinations of any two or more said steps or features. For convenience, before further description of the present invention, certain terms employed in the specification, examples are described here. These definitions should be read in light of the remainder of the disclosure and understood as by a person of skill in the art. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by a person of ordinary skill in the art. The terms used throughout this specification are defined as follows, unless otherwise limited in specific instances. The terms used herein are defined as follows. The term “room temperature” unless stated otherwise, essentially means temperature in range from about 20°C to about 35°C. The term “purity” means purity as determined by high pressure liquid chromatography (HPLC). The term “Cyantraniliprole (I) free of impurities” means cyantraniliprole free of impurities including chemical impurities, volatile impurities and water. The term “Cyantraniliprole (I) substantially free of water” used herein means cyantraniliprole comprising less than 1% of water. The term “crude cyantraniliprole” means cyantraniliprole obtained by methods known to any person ordinarily skilled in art. The term is inclusive of amorphous form of cyantraniliprole, any crystalline form of cyantraniliprole or mixtures thereof. The term “Dielectric constant” of a solvent is a measure of its polarity. A higher dielectric constant means, higher the polarity and greater is the ability of the solvent to stabilize the charge. The term “moisture content” and “water content” are used interchangeably throughout the specification. The term “about” or “approximately” as used herein is inclusive of the stated value and means within an acceptable range of deviation for particular value as determined by one of ordinary skill in the art, considering the measurement in question and the error associated with measurement of the particular quantity (i.e., the limitations of the measurement system). For example, “about” can mean within one or more standard deviations, or within ± 10 or ± 5 of the stated value. Recitation of ranges of values are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. The endpoints of all ranges are included within the range and independently combinable. It is understood that where a parameter range is provided, all integers within that range, and tenths thereof, are also provided. For example, “0.1-80%” includes 0.1%, 0.2%, 0.3%, etc. up to 80%. As used herein, the terms “comprising” “including,” “having,” “containing,” “involving,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. The terms “preferred” and “preferably” refer to embodiments of the invention that may afford certain benefits, under certain circumstances. In an embodiment, the aspects and embodiments described herein shall also be interpreted to replace the clause “comprising” with either “consisting of” or with “consisting essentially of” or with “consisting substantially of”. In an aspect of the present invention, there is provided a process for preparation of an anthranilamide compound or a salt thereof. In an embodiment, the present invention provides a process for preparation of cyantraniliprole (I) free of impurities, the process comprising: treating crude cyantraniliprole with at least one solvent having a dielectric constant less than 6. In an embodiment, the term “impurities” comprise water. In an embodiment, the term “impurities” includes chemical impurities and water. The crude cyantraniliprole is prepared according to process known in prior art. In an embodiment, the crude cyantraniliprole comprises more than 1% water. In an embodiment, the crude cyantraniliprole comprises from about 1% to about 8% water. In an embodiment, the crude cyantraniliprole comprises from about 1% to about 5% water. In an embodiment, the crude cyantraniliprole is present in an amorphous form. In an embodiment, the crude cyantraniliprole is present in any crystalline form of cyantraniliprole or a mixture thereof. Series of experiments were performed to identify suitable solvents for isolating cyantraniliprole (I) free of impurities comprising tetrahydrofuran, 2- methyltetrahydrofuran, cyclohexane, o-xylene, m-xylene, p-xylene, mixture of xylenes, mesitylene, chlorobenzene, hexane, or combinations thereof. However, it was observed by the inventors of the present invention that the solvents having dielectric constant 6 or less than 6, gave better results. In an embodiment, the solvent having dielectric constant less than 6 is a non-polar solvent or mixture thereof. In an embodiment, the solvent used is selected from the group comprising cyclohexane, o-xylene, m-xylene, p-xylene, xylene, mixture of xylenes, mesitylene, chlorobenzene, hexane, or mixtures thereof. In an embodiment, the solvent is a mixture of cyclohexane and xylene. In an embodiment, the ratio of cyclohexane to xylene is in a range from about 1:99 to about 99:1. In an embodiment, the ratio of cyclohexane to xylene is in a range from about 60:40 to about 90:10 In an embodiment, the ratio of cyclohexane to xylene is in a range of about 75 to 85 : 15 to 25. In an embodiment, the ratio of cyclohexane to xylene is about 85:15. In another embodiment, the ratio of cyclohexane to xylene is about 80:20. In another embodiment, the ratio of cyclohexane to xylene is about 75:25. In another embodiment, the solvent/s is a mixture of hexane and xylene. The ratio of hexane to xylene is in a range from about 1:99 to about 99:1. In another embodiment, the solvent is a mixture of cyclohexane and chlorobenzene. The ratio of cyclohexane to chlorobenzene is in a range from about 1:99 to about 99:1. In another embodiment, the solvent is a mixture of cyclohexane and mesitylene. The ratio of cyclohexane to mesitylene is in a range from about 1:99 to about 99:1. In an embodiment, the ratio of cyclohexane to mesitylene is in a range from about 60:40 to about 90:10. In another embodiment, the ratio of cyclohexane to mesitylene is about 80:20. In an embodiment, the present invention provides a process for preparation of cyantraniliprole (I) free of impurities, the process comprising treating crude cyantraniliprole with at least one solvent having a dielectric constant less than 6 and a second solvent. In an embodiment, the second solvent is any suitable solvent selected from organic solvent or water. In an embodiment, the treatment of crude cyantraniliprole comprises heating a mixture of crude cyantraniliprole and at least one solvent having a dielectric constant less than 6 at a temperature above 30°C. In an embodiment, the treatment comprises heating a mixture of crude cyantraniliprole and at least one solvent having a dielectric constant less than 6 at a temperature above 40°C. In an embodiment, the treatment comprises heating a mixture of crude cyantraniliprole and at least one solvent having a dielectric constant less than 6 at a temperature in a range from about 40°C to about 180°C. In another embodiment, the treatment further comprises reducing the moisture content of the mixture to less than about 5%, preferably less than about 2%. The moisture content is reduced by conventionally known methods such as distillation. In another embodiment, the moisture content is reduced by azeotropic distillation. The process of the present invention further comprises cooling the mixture and isolation of cyantraniliprole (I) free of impurities. Cyantraniliprole (I) free of impurities obtained according to present invention has more than 95% purity. In another embodiment, cyantraniliprole (I) free of impurities obtained according to present invention is characterized by bulk density and particle size distribution. In an embodiment, there is provided a process for preparation of cyantraniliprole (I) substantially free of impurity, the process comprising: treatment of crude cyantraniliprole with at least one solvent having a dielectric constant less than 6; wherein said impurity is water. In an embodiment, cyantraniliprole (I) substantially free of impurity wherein said impurity is water and wherein the content of water is less than 1%. In another aspect of the present invention, there is provided a process for preparation of cyantraniliprole of formula (I) free of impurities,

the process comprising: a) reacting a compound of formula (III) with a compound of formula (IV) in an organic solvent to obtain a compound of formula (II);

Formula (III) Formula (IV) Formula (II) b) reacting the compound of formula (II) with methyl amine to obtain crude cyantraniliprole; and c) treating the crude cyantraniliprole with at least one solvent having a dielectric constant less than 6 at a temperature in a range from about 40°C to about 180°C and isolating cyantraniliprole of formula (I) free of impurities. The compound of formula (III) and the compound of formula (IV) are prepared by processes known in prior art. In an embodiment, the compound of formula (III) is prepared from 3-Bromo-1-(3- chloro-2-pyridinyl)-1H-pyrazole-5-carboxylic acid having following formula (A)

Formula (A) In an embodiment, the compound of formula (III) is prepared by reacting 3-Bromo- 1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylic acid having formula (A) with a chlorinating agent. The chlorinating agent used is selected from the group comprising thionyl chloride, oxalyl chloride, phosphorus oxychloride, phosphorus trichloride, phosphorus pentachloride, or combinations thereof. In an embodiment, the reaction of 3-Bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole- 5-carboxylic acid having formula (A) with a chlorinating agent is carried out in presence of a solvent. The solvent used is selected from, but not limited to, a halogenated solvent, a hydrocarbon solvent, an ether or a nitrile. In an embodiment, the solvent used is selected from a halogenated solvent such as dichloromethane, dichloroethane, chloroform and the likes; a hydrocarbon solvent such as toluene, xylene and the like; ether such as tetrahydrofuran and the like; or a nitrile like acetonitrile. In an embodiment, the reaction of 3-Bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole- 5-carboxylic acid having formula (A) with a chlorinating agent is carried out in presence of a catalyst. The catalyst used is dimethylformamide. In an embodiment, the compound of formula (III) obtained by reaction of 3-Bromo- 1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylic acid having formula (A) with a chlorinating agent, is not isolated. In an embodiment, the compound of formula (III) is prepared from 3-bromo-1-(3- chloro-2-pyridinyl)-4,5-dihydro-1H-Pyrazole-5-carboxylic acid having formula (B).

In an embodiment, the compound of formula (III) is prepared by subjecting compound of formula (B) to pyrazoline aromatization using a halogenating agent. In an embodiment the halogenating agent is selected from thionyl chloride, phosgene, oxalyl chloride, phosphorus oxychloride, phosphorus trichloride, phosphorus tribromide, phosphorus pentachloride, or combinations thereof. In a preferred embodiment, the halogenating agent is thionyl chloride. In an embodiment, pyrazoline aromatization reaction is carried out in presence of a halogenated hydrocarbon solvent. In an embodiment, the halogenated hydrocarbon solvent is selected from dichloromethane, dichloroethane, trichloromethane, chloroform, carbon tetrachloride and halogenated aromatic hydrocarbons. In an embodiment the pyrazoline aromatization is carried out optionally in the presence of a catalyst. In an embodiment the catalyst is an organic base. In an embodiment the catalyst is triethylamine or dimethylformamide. In an embodiment the reaction is carried out at a temperature from about 30° to about 70°C, preferably at a temperature from about 30° to about 65°C. In another embodiment, the reaction mixture comprising the compound of formula (III) obtained by pyrazoline aromatization of 3-bromo-1-(3-chloro-2-pyridinyl)- 4,5-dihydro-1H-Pyrazole-5-carboxylic acid having formula (B); is reacted with the compound of formula (IV) in step a) of the process. In another embodiment, the reaction mixture comprising the compound of formula (III) obtained by reaction of 3-Bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5- carboxylic acid having formula (A) with a chlorinating agent; is reacted with the compound of formula (IV) in step a) of the process. In an embodiment, the step a) is carried out in an organic solvent selected from, but not limited to, halogenated solvent, hydrocarbon solvent, ether or acetonitrile. In an embodiment, the step a) is carried out in halogenated solvent such as dichloromethane, dichloroethane, chloroform and the likes. In an embodiment, the step a) is carried out in hydrocarbon solvent such as toluene, xylene, heptane, hexane, cyclohexane and the likes. In an embodiment, the step a) is carried out in acetonitrile. In an embodiment, the step a) is carried out at a temperature in the range from about 30°C to about 120°C. In an embodiment, the compound of formula (II) obtained in step a) is not isolated. In another embodiment, the compound of formula (II) obtained in step a) is isolated. In another embodiment, step a) further comprises step of isolating compound of formula (II) and treating with the compound of formula (II) obtained in step a) is isolated and treated with a solvent. In an embodiment, the solvent used for treatment of the compound of formula (II) is selected from water, organic solvent or mixture thereof. The organic solvent used is selected from alcohol, halogenated solvents, nitriles or mixtures thereof. In another embodiment, step a) comprises isolating the obtained compound of formula (II) and treating with a solvent selected from alcohol, halogenated solvents, nitriles or mixtures thereof. In an embodiment, the organic solvent is selected from alcohols, halogenated solvents, nitriles, or mixtures thereof. The organic solvent is selected from, but not limited to, alcohols like methanol, ethanol; halogenated solvents like dichloromethane; nitriles like acetonitrile and so on. In another embodiment, step a) comprises isolating the obtained compound of formula (II) and treating with a solvent selected from water, organic solvent, or mixtures thereof. In an embodiment, the compound of formula (II) obtained according to present invention has purity of more than 95%, preferably more than 98%. The purity of compound of formula (II) directly impacts purity of final cyantraniliprole obtained. Hence, it is important to obtain purified compound of formula (II). In an embodiment, the methylamine used in step b) is either gaseous methylamine or an aqueous solution of methylamine. In an embodiment, reaction is carried out by purging methylamine gas. In an embodiment methyl amine gas is purged at a temperature range from about 0°C to about 35°C. In an embodiment, methyl amine gas is purged from about 1 to about 12 hours. In an embodiment, the step b) of the process is carried out in an organic solvent. The organic solvent such as halogenated solvent, hydrocarbon solvent, ethers or nitriles is used. In an embodiment, the step b) is carried out in an organic solvent selected from halogenated hydrocarbon solvent like dichloromethane, dichloroethane; an ether like tetrahydrofuran; or nitriles like acetonitrile. In an embodiment, the step b) is carried out in acetonitrile. In an embodiment, the step c) of the process ensures removal of residual water, water of hydration and other volatile impurities from crude cyantraniliprole to obtain cyantraniliprole (I) substantially free of water. In an embodiment, the solvent use in step c) is selected from the group comprising o-xylene, m-xylene, p-xylene, mixture of xylenes, cyclohexane, mesitylene, chlorobenzene, hexane or mixture thereof. In an embodiment, the solvent used in step c) is a mixture of xylene/s and cyclohexane. In another embodiment, the solvent used in step c) is a mixture of xylene/s and hexane. In another embodiment, the solvent used in step c) is a mixture of cyclohexane and chlorobenzene. In another embodiment, the solvent used in step c) is a mixture of cyclohexane and mesitylene. In an embodiment, the step c) treatment comprises heating a mixture of crude cyantraniliprole and at least one solvent having a dielectric constant less than 6 at a temperature above 30°C. In an embodiment, the step c) treatment comprises heating a mixture of crude cyantraniliprole and at least one solvent having a dielectric constant less than 6 at a temperature in the range from about 40°C to about 180°C. In another embodiment, the step c) treatment further comprises reducing the moisture content of the reaction mixture to less than 5%, preferably less than 2%. The moisture content is reduced by conventionally known methods such as distillation. In another embodiment, the moisture content is reduced by azeotropic distillation. The process of the present invention further comprises cooling the mixture and isolation of cyantraniliprole free of impurities. In an embodiment, the process of present invention provides in step c) cyantraniliprole (I) free of impurities, wherein the impurities comprise water. In an embodiment, the process of present invention provides in step c) cyantraniliprole (I), which is substantially free of water. In an embodiment, the process of present invention provides in step c) cyantraniliprole (I) having less than 1% water. In another embodiment, there is provided a process for preparation of cyantraniliprole (I) substantially free of impurity;

Formula (III) Formula (IV) Formula (II) b) reacting the compound of formula (II) with methyl amine to obtain crude cyantraniliprole; and c) treating the crude cyantraniliprole with at least one solvent having a dielectric constant less than 6 and isolating cyantraniliprole (I) substantially free of impurity; wherein said impurity is water. In an embodiment, cyantraniliprole (I) is substantially free of impurity; wherein said impurity is water and wherein content of water is less than 1%. In an aspect of the present invention, there is provided cyantraniliprole (I) comprising more than 95% purity and less than 1% water. It is observed that the cyantraniliprole (I) obtained by process according to present invention remains stable without significant change in water content, thereby making it suitable for further use. In an embodiment, cyantraniliprole (I) obtained according to present invention characterized by a X-ray powder diffraction pattern exhibiting at least one peak selected from 6.62, 10.32, 10.89, 11.67, 13.67, 14.59, 15.21, 15.47, 16.45, 18.33, 18.65, 19.15, 19.74, 20.71, 21.89, 22.34, 22.96, 23.92, 24.30, 25.03, 25.83, 26.72, 29.74, 31.372Ɵ ± 0.2° 2Ɵ. In an embodiment, cyantraniliprole obtained according to present invention is having an X-ray powder diffraction pattern as shown in Figure 1. In an embodiment, cyantraniliprole (I) obtained according to the present invention comprising bulk density from about 0.4 mg/ml to about 0.8 mg/ml. In an embodiment, provides a novel crystalline compound of formula (II). In an embodiment, there is provided a crystalline compound of formula (II) characterized by data selected from the group comprising: i) a X-ray powder diffraction pattern exhibiting at least one peak selected from 11.91, 15.00, 15.82, 16.79, 18.23, 18.51, 19.53, 20.57, 21.81, 23.49, 23.88, 24.06, 24.48, 25.25, 25.89, 27.25, 28.09, 29.42, 30.28, 31.212Ɵ ± 0.2° 2Ɵ; ii) a differential scanning calorimetric (DSC) thermogram having an endotherm at about 203°C to about 208°C. iii) an infrared spectrum exhibiting at least one peak selected from 3749, 3649, 3245, 3124, 3028, 3002, 2953, 2323, 2225, 1698, 1471, 1441, 1378, 1338, 1296, 1282, 1237, 1141, 993, 901, 878, 822, 813, 794, 783, 755, 744, 659, 600 (cm^-1 ± 2). In an aspect of the present invention, there is provided a crystalline compound of formula (II) characterized by an X-ray powder diffraction pattern. In an embodiment, the present invention provides the crystalline compound of formula (II) having an X-ray powder diffraction pattern exhibiting at least one peak selected from group comprising 11.91, 15.00, 15.82, 16.79, 18.23, 18.51, 19.53, 20.57, 21.81, 23.49, 23.88, 24.06, 24.48, 25.25, 25.89, 27.25, 28.09, 29.42, 30.28, 31.212Ɵ ± 0.2° 2Ɵ. In an embodiment, the present invention provides the crystalline compound of Formula (II) having X-ray powder diffraction pattern as shown in Figure 2. In an embodiment, the present invention provides the crystalline compound of Formula (II) having differential scanning calorimetric (DSC) thermogram having endotherm from about 203°C to about 208°C. In an embodiment, the present invention provides the crystalline compound of Formula (II) having differential scanning calorimetric (DSC) thermogram as shown in Figure 3. In an embodiment, the present invention provides the crystalline compound of Formula (II) exhibiting Fourier transform infrared (FTIR) spectrum with peaks at wavenumbers 3749, 3649, 3245, 3124, 3028, 3002, 2953, 2323, 2225, 1698, 1471, 1441, 1378, 1338, 1296, 1282, 1237, 1141, 993, 901, 878, 822, 813, 794, 783, 755, 744, 659, 600 (cm^-1 ± 0.2%). In an embodiment, the crystalline compound of formula (II) having Fourier transform infrared (FTIR) spectroscopy as shown in Figure 4. In an embodiment, the compound of formula (II) having purity above 98% is obtained. In an embodiment, the present invention provides a process for the preparation of cyantraniliprole; wherein the process proceeds via a crystalline form of the compound of formula (II). In an embodiment, the crystalline compound of formula (II) according to present invention is used for preparation of cyantraniliprole (I). Advantages of the present invention: 1. The present invention provides a highly pure cyantraniliprole. 2. The present invention provides a process for preparation of cyantraniliprole, which is free of impurities. 3. The present invention provides a crystalline form of compound of formula (II) having high purity. 4. The present invention also provides process for preparation of crystalline form of compound of formula (II). 5. The processes provided in present invention are industrially viable, simple and economical. EXAMPLES: The following examples are presented to provide what is believed to be the most useful and readily understood description of procedures and conceptual aspects of this invention. The examples provided below are merely illustrative of the invention and are not intended to limit the same to disclosed embodiments. Variations and changes obvious to one skilled in the art are intended to be within the scope and nature of the invention. Analytical Method Details: 1. X‐ray powder diffraction method (XPRD) pattern was carried out on Bruker make 2^nd generation D2 Phaser Powder X-Ray diffractometer; 2. Differential scanning calorimetry (DSC) thermogram was measured by a Differential scanning calorimeter (DSC-3, Mettler Toledo) having temperature range of 40°C to 250°C with 5.00 K/min, N220.0 ml/min; 3. Infrared Spectroscopy: IR spectra were acquired using a PerkinElmer make Spectra Two IR spectrophotometer; 4. High-performance liquid chromatography (HPLC) HPLC Column: COSMOSIL -5C18-MS-II (250 mm x 4.6 mm, 5 μm) Mobile Phase - a) Water (0.1% H3PO4) b) Acetonitrile Example 1: Process for preparation of 3-Bromo-1-(3-chloro-2-pyridinyl)-1H- pyrazole-5-carbonyl chloride (compound of formula III) To a mixture of 350g 3-Bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylic acid (compound A) and 1400g (1055ml) dichloromethane, 0.5g dimethyl formamide was added, and the mixture was then heated to 45°C to 50°C and slowly 192g of thionyl chloride was slowly added to it. After completion of reaction, the solvent was recovered and the reaction mass comprising 3-Bromo-1-(3-chloro-2- pyridinyl)-1H-pyrazole-5-carbonyl chloride i.e., compound of formula (III) was obtained. Example 2: Process for preparation of Methyl 2- bromo-1-(3-chloro-2-

pyridinyl)-1H-pyrazol-5-yl]carbonyl]amino]-5-cyano-3-methylbenzoate- compound of formula (II) The mixture of 150g methyl 2-amino-5-cyano-3-methylbenzoate i.e., compound of formula (IV) and 450g (572ml) of acetonitrile was heated to 65°C to 75°C and to this mixture was added slowly 1065g compound of formula (III) obtained in Example 1. The mixture was maintained at 70°C to 75°C for about 5 to 6 hours. After completion of reaction, acetonitrile was recovered by distillation and the mixture was filtered at 40°C to 45°C to obtain a wet cake. The wet cake was then washed with 5% soda ash solution, water and acetonitrile and the solid were dried at 60°C to 70°C to obtain 330g of compound of formula (II) having purity of 98.32%. Example 3: Process for preparation of crude cyantraniliprole of formula (I) The mixture of 150g compound of formula (II) and 450g (572ml) acetonitrile was cooled to 5°C to 10°C and 59g of methylamine gas was purged into the mixture for 3 to 5 hours. The mixture was maintained at 15°C to 20°C for another 4 hours. After completion of reaction, acetonitrile was partially recovered by distillation and then the mixture was filtered at 45°C to obtain wet cake. This wet cake was washed with water and acetonitrile and dried to get a crude cyantraniliprole of formula (I) having purity of 94.53%. Example 4: Process for preparation of cyantraniliprole (I) substantially free of water impurity[using mixture of cyclohexane and xylene/s (80:20)] To the crude cyantraniliprole obtained in Example 3 was added mixture of cyclohexane and xylene [360g (465ml) cyclohexane and 90g (104ml) mixture of xylenes] and the mixture was heated to 75°C to 85°C. The moisture content of the mixture was then reduced to below 0.1% by azeotropic distillation at same temperature. The mixture was then cooled to room temperature, filtered, and dried to obtain 112g cyantraniliprole (I) having purity of 96.66% (moisture content: 0.27%). Example 5: Process for preparation of cyantraniliprole (I) substantially free of water impurity [using mixture of cyclohexane and xylene/s (85:15)] To the 98g crude cyantraniliprole obtained in similar way as in Example 3, was added mixture of cyclohexane and xylene [250g (323ml) cyclohexane and 44g (51ml) mixture of xylenes] and the mixture was heated to 85°C to 90°C. The moisture content of the mixture was then reduced to below 0.1% by azeotropic distillation at same temperature. The mixture was then cooled to room temperature, filtered, and dried to obtain 86g cyantraniliprole (I) having purity of 97.41% (moisture content: 0.43%). Example 6: Process for preparation of cyantraniliprole (I) substantially free of water impurity [using mixture of cyclohexane and xylene/s (75:25)] To the 140g wet cake of crude cyantraniliprole (obtained in similar way as in Example 3), was added mixture of cyclohexane and xylenes [315g (407ml) cyclohexane and 105g (121ml) mixture of xylenes] and the mixture was heated to 85°C to 90°C. The moisture content of the mixture was then reduced to below 0.1% by azeotropic distillation at same temperature. The mixture was then cooled to room temperature, filtered, and dried to obtain 121g Cyantraniliprole (I) having purity of 96.64% (moisture content: 0.61%). Example 7: Process for preparation of cyantraniliprole (I) substantially free of water impurity [using mixture of cyclohexane and mesitylene (80:20)] To the 92g wet cake of crude cyantraniliprole (92g, obtained in similar way as in Example 3), was added mixture of cyclohexane and mesitylene [220.8g (285ml) cyclohexane and 55.2g (64ml) mesitylene] and the mixture was heated to 85°C to 90°C. The moisture content of the mixture was then reduced to below 0.1% by azeotropic distillation at same temperature. The mixture was then cooled to room temperature, filtered, washed, and dried to obtain 70g cyantraniliprole (I) having purity of 96.96% (moisture content: 0.072%). Example 8: Chemical and physically stability of cyantraniliprole obtained in Examples 3-7 The chemically and physically stability of cyantraniliprole obtained in Examples 3, 4, 5, 6 & 7 was determined by storing the 10g sample at ambient conditions for 1 month. The samples were tested by Karl-fisher titrator and HPLC for purity and moisture content. The results are given in Table 1. Table 1

The cyantraniliprole obtained in Examples 4, 5, 6 & 7 was found to be chemically and physically very stable. There was no substantial change in moisture content or purity of cyantraniliprole, however there was increase in water content i.e., impurity in Example 3 on storage.

Claims

We claim: 1. A process for preparation of cyantraniliprole (I) free of impurities, the process comprising treating crude cyantraniliprole with at least one solvent having a dielectric constant less than 6.

2. The process as claimed in claim 1, wherein the crude cyantraniliprole comprises more than 1% water.

3. The process as claimed in claim 1, wherein the solvent is selected from the group comprising cyclohexane, o-xylene, m-xylene, p-xylene, xylene, mixture of xylenes, mesitylene, chlorobenzene, hexane, or mixtures thereof.

4. The process as claimed in claim 3, wherein the solvent is a mixture of cyclohexane and xylene.

5. The process as claimed in claim 4, wherein the ratio of cyclohexane to xylene is in a range from about 1:99 to about 99:1.

6. The process as claimed in claim 5, wherein the ratio of cyclohexane to xylene is in a range of about 75 to 85 : 15 to 25.

7. The process as claimed in claim 3, wherein the solvent is a mixture of cyclohexane and mesitylene.

8. The process as claimed in claim 7, wherein the ratio of cyclohexane to mesitylene is in a range from about 1:99 to about 99:1.

9. A process for preparation of cyantraniliprole of formula (I) free of impurities, 1 Formula (I) the process comprising: a) reacting a compound of formula (III) with a compound of formula (IV) in an organic solvent to obtain a compound of formula (II);

Formula (III) Formula (IV) Formula (II) b) reacting the compound of formula (II) with methyl amine to obtain crude cyantraniliprole; and c) treating the crude cyantraniliprole with at least one solvent having a dielectric constant less than 6 at a temperature in a range from about 40°C to about 180°C and isolating cyantraniliprole of formula (I) free of impurities.

10. The process as claimed in claim 9, wherein the step a) comprises isolating the obtained compound of formula (II) and treating with a solvent selected from water, organic solvent, or mixtures thereof.

11. The process as claimed in claim 10, wherein the organic solvent is selected from alcohols, halogenated solvents, nitriles, or mixtures thereof. 2

12. Cyantraniliprole (I) comprising more than 95% purity and less than 1% water.

13. Cyantraniliprole (I) comprising bulk density from about 0.4 mg/ml to about 0.8 mg/ml.

14. Cyantraniliprole (I) characterized by a X-ray powder diffraction pattern exhibiting at least one peak selected from 6.62, 10.32, 10.89, 11.67, 13.67, 14.59,

15.21, 15.47,

16.45, 18.33, 18.65, 19.15, 19.74, 20.71, 21.89, 22.34, 22.96, 23.92, 24.30, 25.03, 25.83, 26.72, 29.74, 31.372Ɵ ± 0.2° 2Ɵ. 15. A crystalline compound of formula (II) characterized by data selected from the group comprising: i) a X-ray powder diffraction pattern exhibiting at least one peak selected from 11.91, 15.00, 15.82, 16.79, 18.23, 18.51, 19.53, 20.57, 21.81, 23.49, 23.88, 24.06, 24.48, 25.25, 25.89, 27.25, 28.09, 29.42, 30.28, 31.212Ɵ ± 0.2° 2Ɵ; ii) a differential scanning calorimetric (DSC) thermogram having an endotherm at about 203°C to about 208°C. iii) an infrared spectrum exhibiting at least one peak selected from 3749, 3649, 3245, 3124, 3028, 3002, 2953, 2323, 2225, 1698, 1471, 1441, 1378, 1338, 1296, 1282, 1237, 1141, 993, 901, 878, 822, 813, 794, 783, 755, 744, 659, 600 (cm^-1 ± 2). 3