DESC:

FORM 2

THE PATENT ACT, 1970
(39 of 1970)

COMPLETE SPECIFICATION
(Section 10, rule 13)

“AN IMPROVED PROCESS FOR PREPARATION OF CYANTRANILIPROLE OR SALT THEREOF”

We, LAURUS LABS LIMITED, an Indian Company of DS-1, IKP Knowledge Park, Genome Valley, Turkapally, Shameerpet Mandal, Medchal-Malkajgiri District,
Hyderabad-500 101, Telangana, INDIA

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

FIELD OF THE INVENTION

The present invention relates to process for preparation of 2-amino-5-cyano-N, 3-dimethyl benzamide, an intermediate for preparation of cyantraniliprole or a salt thereof.The present invention alsorelates to an improved process for preparation of crystalline polymorph of cyantraniliprole.

BACKGROUND OF THE INVENTION

Cyantraniliprole is a second-generation anthranilicdiamide insecticide discovered by DuPont Crop Protection and is chemically known as 3-bromo-1-(3-chloro-2-pyridyl)-4'-cyano-2'-methyl-6'-(methylcarbamoyl)pyrazole-5-carboxanilide.

Known methods for the preparation of cyantraniliprole proceeds with 2-Amino-5-cyano-N,3-dimethyl benzamide(Formula V) which is a key intermediate and main cost contributor in the preparation of cyantraniliprole.

PCT application No. 2006/062978 (“the ‘978 publication”) discloses a process for preparation of compound of Formula V, as follows:

U.S. Patent No. 8,748,630 (“the ‘630 patent”) discloses a process for preparation of compound of Formula V, as follows:

U.S. Patent No. 8,049,029 (“the ‘029 patent”) discloses a process for preparation of compound of Formula V, as follows:

PCT application No. 2010/056720 (“the ‘720 publication”) discloses preparation of Cyantraniliprole non-hydratable crystal Form A from a hydratable crystal Form B by heating at a temperature between about 40°C and the boiling point of the solvent, wherein the solvent is selected from the group consisting of water, n-heptane, 1- chlorobutane, toluene, 1-butanol and 1-pentanol.

PCT application No. 2021/249395 (“the ‘395 publication”) discloses solid state forms C, D and F of cyantraniliprole and their preparation.

PCT application No. 2023/095161 (“the ‘161 publication”) discloses process for the preparation of crystalline Form A of cyantraniliprole from solvent selected from methyl cyclohexane, xylene and mixtures thereof.

There is a need for animproved process for preparation of cyantraniliproleintermediate compound of formula V and thereafter cyantraniliprole, which providessimple, efficient, economic and reproducible process, particularly on large scale.

Therefore, the present invention fulfills the need in the art and provides simple, industrially feasible and scalable processes for the preparation of cyantraniliproleintermediate compound of formula V and use in the preparation of cyantraniliprole, particularly in the preparation of crystalline Form of cyantraniliprole.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides an improved process for preparation of
compound of Formula V which is convenient, economical, and environment friendly,
wherein the process employs a one-pot process with minimum isolation andpurification steps and also minimum wastage of material. Further, the presentinvention provides an improved process for preparation of cyantraniliprole throughpreparing the compound of Formula V.

Further, the present invention provides an improved process for preparation ofcrystalline Form of cyantraniliprole, particularly crystalline Form A ofcyantraniliprole.

In accordance with one embodiment, the present invention provides an improved process for preparation of compound of Formula V, comprising:

a) reacting a compound of Formula I with a source of bromide in a suitable solvent to obtain a compound of Formula II,

b) reacting the compound of Formula II with phosgene or its derivative and a suitable base to obtain a compound of Formula III,

c) reacting the compound of Formula III with a source of monomethyl amine to obtain a compound of Formula IV, and

d) reacting the compound of formula IV with cyanide sourceto obtain a compound of Formula V.

In accordance with another embodiment, the present invention provides an improved process for preparation of compound of Formula V, comprising:
a) reacting a compound of Formula I with a source of bromide in a suitable solvent to obtain a compound of Formula II,
b) reacting the compound of Formula II with phosgene or its derivative and a suitable base to obtain a compound of Formula III,
c) reacting the compound of Formula III with a source of monomethyl amine to obtain a compound of Formula IV, and
d) reacting the compound of formula IV with cyanide sourceto obtain a compound of Formula V; wherein the steps a) to d) are carried out in one-pot reaction.

In accordance with another embodiment, the present invention provides an improved process for preparation of compound of Formula V as defined just as above, wherein the steps a) to c) are carried out in one-pot reaction.

In accordance with another embodiment, the present invention provides an improved process for preparation of compound of Formula V, comprising:
a) reacting a compound of Formula I with a source of bromide in a suitable solvent to obtain a reaction solution of compound of Formula II,
b) reacting the step a) solution of compound of Formula II with phosgene or its derivative and a suitable base to obtain a reaction solution of compound of Formula III,
c) reacting the step b) solution of compound of Formula III with a source of monomethyl amine,
d) optionally, removing the organic solvent,
e) optionally, adding an organic solvent to the step d) reaction mass,
f) treating step e) reaction mass with cyanide sourceto obtain a compound of Formula V, and
g) isolating the compound of Formula V.

In accordance with another embodiment, the present invention provides an improved process for preparation of cyantraniliprole, comprising:

a) preparing a compound of Formula V according to processes described as above, and
b) converting the compound of Formula V in to cyantraniliprole.

In accordance with another embodiment, the present invention provides an improved process for preparation of crystalline Form A of cyantraniliprole, comprising:
a) providing cyantraniliprole in a suitable solvent or mixture of solvents,
b) heating the step a) reaction mixture to a temperature from about 50°C to reflux,and
c) isolatingcrystalline Form A of cyantraniliprole.

In accordance with another embodiment, the present invention provides an improved process for preparation of crystalline Form A of cyantraniliprole, comprising:
a) providing cyantraniliprole in a suitable solvent or mixture of solvents,
b) heating the step a) reaction mixture to a temperature from about 50°C to reflux,
c) cooling the step b) reaction mass to a temperature of about 10°C to about 50°C, and
d) isolatingcrystalline Form A of cyantraniliprole.

In accordance with another embodiment, the present invention provides an improved process for preparation of crystalline Form A of cyantraniliprole, comprising:
a) providing crystalline Form B of cyantraniliprole in a suitable solvent or mixture of solvents,
b) heating the step a) reaction mixture to a temperature from about 50°C to reflux,and
c) isolatingcrystalline Form A of cyantraniliprole.

In accordance with another embodiment, the present invention provides a composition comprising cyantraniliprole or crystalline Form A of cyantraniliprole, prepared by the process of the present invention and/or at least one excipient.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1: PXRD of crystalline Form A of Cyanthraniliprole obtained according to Example 3.

DETAILED DESCRIPTION OF THE INVENTION

The present invention encompasses an improved process for the preparation of compound of Formula V with high product yield and quality, wherein the improvements involve use of one-pot process without isolating intermediate compounds thereby avoiding multiple solvent systems and cumbersome isolations such as time consuming solvent workups, drying and necessity of analyzing the compounds at each stage.

The processes disclosed under thereported literature suffers from one or more of the following disadvantages:
1. Carrying out isolation of process intermediates as solid compounds which necessarily involves additional process steps such as workup, filtration, drying and packing with specified controlled conditions, which are tedious, labor intensive, time consuming, increasing reactor occupancy and loss of valuable material thereby not viable for commercial scale operations;
2. Use of multiple solvents for each reaction step and isolation thereby generating considerable waste and is not recommended on large scale;
3. Use of hydrogen peroxide in bromination process which is a strong oxidizer and may cause fire or explosion;
4. Sophisticated use of gaseous bromine wherein the process involves flowing an inert gas below the surface of liquid bromine and allowing bromine vapor entrained to enter the vessel containing the reaction mixture, which makes the process cumbersome;
5. Use of multiple metal catalysts and ligand resulting in product contaminated with heavy metal and then increasing the cost of manufacturing dramatically;
6. Use of costly zinc cyanide;
7. Use of sodium cyanide by powdering it just before use and handling sodium cyanide while powdering makes the process more complicated and dangerous;
8. Involves longer reaction times of about 25 hrs during cyanation reaction, which makes the process uneconomical; and
9. The reported methods for the preparation of crystalline Form of cyantraniliprole, particularly of cyantraniliprole crystalline Form A involve requirement of longer maintenance times, use of sophisticated equipment in some instances making the process difficult to carry out on largescale and longer drying times even up to 3 days which is not feasible on largescale.

The present invention fulfills the need in the art and provides simple, industrially feasible and scalable processes for the preparation of cyantraniliprole intermediate compound of formula V and thereafter cyantraniliprole that circumvent disadvantages associated with the prior art process, proved to be advantageous from environmental and industrial point of view and fulfill purity criteria. These processes allow the final product to be produced in a higher yield and purity by minimizing number of processing steps and reducing the number of solvents used which is very practical for scale-up production, especially in terms of operating efficiency.

In accordance with one embodiment, the present invention provides an improved process for preparation of compound of Formula V, comprising:

a) reacting a compound of Formula I with a source of bromide in a suitable solvent to obtain a compound of Formula II,

b) reacting the compound of Formula II with phosgene or its derivative and a suitable base to obtain a compound of Formula III,

c) reacting the compound of Formula III with a source of monomethyl amine to obtain a compound of Formula IV, and

d) reacting the compound of formula IV with cyanide sourceto obtain a compound of Formula V.

In another embodiment, the present invention provides an improved process for preparation of compound of Formula V, wherein the steps a) to d) are carried out in one-pot reaction without isolating the intermediates II to IV as solid.

The term "one-pot" as used in this application means the process uses a strategy to improve the efficiency of a chemical reaction whereby a reactant is subjected to successive chemical reactions in just one or two solvents/reactor. This is much desired by chemists because avoiding a lengthy separation process and purification of the intermediate chemical compounds can save time and resources, improves the efficiency of a chemical reaction, avoids contact of hazardous materials, reduces reactor occupancy, and offers better chemical yield.

The source of bromide used in aforementioned step a) is selected from the group consisting of but not limited to elemental bromine either in gaseous form or in liquid form, sulfuryl bromide, N-bromosuccinimide, mixture of metal bromide-hydrogen peroxide in acid aqueous medium, mixture of hydrogen bromide-hydrogen peroxide,
Metal bromide/metal periodate combination in acidic medium, m-chloroperbenzoic acid/ hydrogen bromide, acetyl bromide, 1,3-dibromo-5,5-dimethylhydantoin and the like, preferably elemental bromine either in gaseous form or in liquid form.

The suitable solvent used in aforementioned step a) is selected from the group consisting of but not limited to amides, esters, ketones, nitriles, ethers, halogenated hydrocarbons, aromatic hydrocarbons and the like and mixtures thereof. The amides include, but are not limited to dimethylacetamide, dimethylformamide, N-methylpyrrolidone and the like and mixtures thereof; esters include, but are not limited to ethyl acetate, methyl acetate and the like and mixtures thereof; ketones include, but are not limited to acetone, methyl isobutyl ketone, methyl ethyl ketone and the like and mixtures thereof; nitriles include, but are not limited to acetonitrile, propionitrile and the like and mixtures thereof; ethers include, but are not limited to tetrahydrofuran, methyl tetrahydrofuran, dimethyl ether, diisopropyl ether, methyl tertiary butyl ether, 1,4-dioxane and the like and mixtures thereof; halogenated hydrocarbons include, but are not limited to methylene chloride, ethylene chloride, chloroform and the like and mixtures thereof; aromatic hydrocarbons include, but are not limited to toluene, xylene and the like and mixture thereof, preferably methylene chloride.

The reaction of a Formula I with a source of bromide may be carried out at a temperature of about -10°C to reflux temperature of the solvent, preferably about -10°C to about 20°C and stirred for a period of time from about 30mins to until completion of reaction, preferably 30 minutes to about 5 hours.

After completion of the step a) reaction, the resulting reaction mass may be advantageously proceeded to next step by adding phosgene or its derivative and a suitable base to the step a) reaction mass without isolating the compound of Formula II as solid.

The phosgene or its derivative as used in the aforementioned step b) can be in any form such as solid, liquid or gas and is selected from the group consisting of but not limited to phosgene, diphosgene, triphosgene, bromophosgene and the like, preferably triphosgene.

The suitable base used in aforementioned step b) is selected from the group consisting of but not limited to inorganic bases selected from alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide and the like; alkali metal alkoxides such as sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium tert-butoxide and the like; alkali metal carbonates such as sodium carbonate, potassium carbonate, cesium carbonate and the like; alkali metal bicarbonates such as sodium bicarbonate, potassium bicarbonate and the like; organic bases selected from the group comprising of triethylamine, isopropyl ethylamine, diisopropyl amine, diisopropyl ethylamine, N-methyl morpholine, piperidine, 2-picoline, 3-picoline and the like and mixtures thereof, preferably selected from sodium bicarbonate, potassium bicarbonate or sodium carbonate.

The reaction of Formula II with phosgene or its derivative may be carried out at a temperature of about 0°C to reflux temperature, preferably about 10°C to about 50°C and stirred for a period of 2hours to until completion of the reaction, preferably 4 hours to about 8 hours.

After completion of the step b) reaction, the resulting reaction mass may be advantageously continued to next step by adding a source of monomethylamine without isolating the compound of Formula III as a solid.

The source of monomethyl amine used in aforementioned step c) is selected from the group consisting of aqueous methylamine, methylamine in solvent, methylamine gas and the like, preferably aqueous methylamine.

Optionally, the step c) is carried out in presence of a suitable acid or a suitable base. The suitable acid optionally used in aforementioned step c) is selected from the group consisting of acetic acid, formic acid, propionic acid, chloroacetic acid, benzoic acid, phthalic acid, maleic acid, tartaric acid and citric acid and the like. The suitable base optionally used in aforementioned step c) is selected from the group consisting of but not limited to inorganic bases selected from alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide and the like; alkali metal alkoxides such as sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium tert-butoxide and the like; alkali metal carbonates such as sodium carbonate, potassium carbonate, cesium carbonate and the like; alkali metal bicarbonates such as sodium bicarbonate, potassium bicarbonate and the like; organic bases selected from the group comprising of triethylamine, isopropyl ethylamine, diisopropyl amine, diisopropyl ethylamine, N-methyl morpholine, piperidine, pyridine, 2-picoline, 3-picoline and the like and mixtures thereof.

The reaction of compound of Formula III with a source of monomethylamine is carried out at a temperature of about 10°C to reflux temperature, preferably about 10°C to about 50°C; and stirred for a period of 3 hours to until completion of the reaction, preferably about 8 hours to about 12 hours.

In one embodiment, after completion of the step c) reaction, the resultant reaction mass can be continued directly to step d) reaction in the same solvent without involving any additional process steps such as isolation and purification of formed intermediate compound of formula IV.

In another embodiment, after completion of the step c) reaction, water may be added to the reaction mass, aqueous layer separated and the organic layer may be concentrated at below 50°C. Then the obtained compound of Formula IV can be carried forward to next step for cyanation reaction without isolation and purification of Formula IV by adding cyanide source and a second solvent.

The suitable second solvent used in aforementioned step d) is selected from the groupconsisting of but not limited to amides, esters, ketones, nitriles, ethers, halogenated hydrocarbons, aromatic hydrocarbons and the like and mixtures thereof. The amides include, but are not limited to dimethylacetamide, dimethylformamide, N-methylpyrrolidone and the like and mixtures thereof; esters include, but are not limited to ethyl acetate, methyl acetate and the like and mixtures thereof; ketones include, but are not limited to acetone, methyl isobutyl ketone, methyl ethyl ketone and the like and mixtures thereof; nitriles include, but are not limited to acetonitrile, propionitrile and the like and mixtures thereof; ethers include, but are not limited to tetrahydrofuran, methyl tetrahydrofuran, dimethyl ether, diisopropyl ether, methyl tertiary butyl ether, 1,4-dioxane and the like and mixtures thereof; halogenated hydrocarbons include, but are not limited to methylene chloride, ethylene chloride, chloroform and the like and mixtures thereof; aromatic hydrocarbons include, but are not limited to toluene, xylene and the like and mixture thereof, preferably xylene.

Step d) of the aforementioned process involves reacting compound IV with a cyanide source selected from the group consisting of but not limited to barium cyanide, calcium cyanide, copper cyanide, sodium cyanide, potassium cyanide, zinc cyanide, cesium cyanide, cobalt cyanide, ammonium cyanide, trimethylsilyl cyanide, potassium ferricyanide, sodium ferricyanide and the like and mixtures thereof, preferably sodium cyanide.

The step d) process may optionally be carried out in the presence of a catalyst, a metal halide, a ligand and a base.

The catalyst comprises one or more compounds selected from the group consisting of palladium, nickel, copper, zinc (e.g., palladium chloride, palladium acetate, zinc metal, chloro-1-naphthalenylbis(triphenylphosphine)-nickel, tris(dibenzylidene- acetone)dipalladium, tetrakis(triphenylphosphine) palladium(0), dichlorobis- (triphenylphosphine) palladium(II)] and the like).

The metal halide used is selected from the group comprising of cuprous iodide, zinc iodide, sodium iodide, potassium iodide and the like and mixtures thereof, preferably cuprous iodide.

Ligands in general can be neutral or charged, and can be unidentate, bidentate or higher and can be selected from the group comprising triphenylphosphine, tri-tert-butylphosphine, tri-tert-butylphosphoniumtetrafluoroborate, di-tert-butylneopentylphosphine, di-tert-butylneopentylphosphoniumtetrafluoroborate, di-tert-butylcyclohexylphosphine, di-tert-butylphenylphosphine, di-tert-butylisopropylphosphine, 1,4-bis(diphenylphosphino)butane, 1,3-bis(diphenylphosphino)-propane, 1,1'-bis(diphenylphosphino)ferrocene (dppf) and benzyl-di-1-adamantyl-phosphine. N,N'-dimethylethylenediamine, N,N'-dimethyl-1,3-propanediamine, 2,2-dimethyl-1,3-propanediamine and the like and mixtures thereof, preferably N,N'-dimethylethylenediamine.

The base comprises one or more selected from the group consisting of inorganic bases such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium acetate, potassium acetate, sodium propionate, potassium propionate and the like; and organic bases such as triethylamine, tert-butylamine, pyridine, 3-picoline, 4-picoline, 4-ethylpyridine, 4-tert-butylpyridine, 3,4-lutidine, 3,5-lutidine, 4-methoxypyridine, 4-(dimethylamino)pyridine, 4-(diethylamino)pyridine, 4-pyrrolidinopyridine and 4-morpholinopyridine, 1-methyl-1H-imidazole, 1-ethyl-1H-imidazole, 1-propyl-1H-imidazole, 1-butyl-1H-imidazole, 1-pentyl-1H-imidazole, 1-hexyl-1H-imidazole, 4-methylimidazole, 1,1'-(1,4-butanediyl)bis-1H-imidazole, 1,1'-(1,5-pentanediyl)bis-1H-imidazole, 1,1'-(1,6-hexanediyl)bis-1H-imidazole and the like.

The reaction of a Formula IV with a cyanide source is carried out at a temperature of about 25°C to reflux temperature of the solvent, preferably about 110°C to about 150°C and stirred for a period of 30mins to until completion of the reaction, preferably about 2 hours to about 10 hours.

Thereafter, isolation of the resultant compound V may be carried out by conventional techniques known in the art, for example, isolation can be carried out by treating the reaction mass with water, filtering and further drying. Drying can be suitably carried out in a tray dryer, vacuum oven, air oven, fluidized bed drier, spin flash dryer, flash dryer and the like. The drying can be carried out at a temperature ranging from about 20°C to about 100°C.

In another embodiment, the present invention provides an improved process for the preparation of cyantraniliprole or a salt thereof, comprising preparing the compound of Formula V as per the process described above, and converting the compound of Formula V in to cyantraniliprole or a salt thereof by any process known in the art for example WO2006/062978 or by the process described in the present specification.

In accordance with another embodiment, the present invention provides an improved process for preparation of crystalline Form A of cyantraniliprole, comprising:
a) providing cyantraniliprole in a suitable solvent or mixture of solvents,
b) heating the step a) reaction mixture to a temperature from about 50°C to reflux,and
c) isolatingcrystalline Form A of cyantraniliprole.

The starting cyantraniliprole used in the present invention is known in the art and can be synthesized by any known methods, for example starting compound may be obtained according to PCT application Nos. 2004/067528, 2006/062978, 2010/056720, 2021/249395, 2023/095161 or obtained according to the process of the above embodiments, which are incorporated herein by reference. Alternatively, the starting cyantraniliprole may be obtained as a wet solid directly from a reaction mixture in which cyantraniliprole is formed and used as such without drying.

The step a) of providing cyantraniliprole in a solvent or mixture of solvents includes combining cyantraniliprole with a solvent or mixture of solvents at a suitable temperature.

In one embodiment, the term ‘Cyantraniliprole’ used as starting material in step a) may include Cyantraniliprole in any form, or hydrate, clathrate, solvate or their mixtures and in any state of purity, unless specifically mentioned.

In another embodiment, cyantraniliprole used as starting material in step a) may be selected from crystalline Form B, Form C, Form D or Form F of cyantraniliprole.

Examples of suitable solvent include but are not limited to ethyl benzene, methyl isobutyl ketone, methyl ethyl ketone, acetone, cyclopentylmethyl ether, 2-methyl tetrahydrofuran, dibutyl ether, methyl tert. butyl ether, 1,4-dioxane, acetonitrile, methanol, n-propanol, isopropanol, t-butanol, benzyl alcohol, ethyl acetate, n-propyl acetate, isopropyl acetate, cyclohexane, hexane, dichloromethane, dimethyl sulfoxide, and the like and mixtures thereof, preferably ethylbenzene or n-propanol or mixture thereof.

In another embodiment, the suitable solvent used herein is step a) of the above embodiment may include but are not limited to ethyl benzene, ethyl acetate, n-propyl acetate, isopropyl acetate, n-propanol, cyclopentylmethyl ether, 2-methyl tetrahydrofuran, dibutyl ether, methyl tert. butyl ether, methyl ethyl ketone, dichloromethane and the like and mixtures thereof, preferably ethylbenzene, n-propanol or mixture thereof.

The reaction may typically be carried out at a suitable temperature such as about 50°C to reflux temperature of the solvent, preferably about 60°C to about 150°C and stirred for a period of about 5 minutes to about 10 hours, preferably about 10 minutes to about 5 hours.

In another embodiment, the reaction mass containing cyantraniliprole in a suitable solvent of step b) may be subjected to azeotropic distillation.

Thereafter, the resultant reaction mass may be cooled to a temperature of about 10°C to about 60°C or less and stirred at the same temperature. Isolation of the product may be carried out by any of the conventional techniques such as filtration, centrifugation and the like.

The resultant product may optionally be further dried. Drying can be suitably carried out in a tray dryer, vacuum oven, air oven, fluidized bed drier, spin flash dryer, flash dryer and the like. The drying can be carried out at a temperature ranging from about 20°C to about 100°C.

Advantageously, the process of the present disclosure enables the production of highly pure crystalline Form A of Cyantraniliprole, for ex., having a purity of at least 99%, preferably 99.5%, more preferably 99.8%, most preferably 99.9%.

In another embodiment, the present invention provides a composition comprising Cyantraniliprole or crystalline form A of Cyantraniliprole, prepared by the process of the present invention and/or at least one excipient.

The present invention provides compound of Formula V or Cyantraniliprole, obtained by the above process, as analyzed using high performance liquid chromatography ("HPLC") with the conditions are tabulated below:

Column Zorbax RX C8
Mobile phase Buffer, water and Acetonitrile
Buffer potassium dihydrogen phosphate
Diluent water and Acetonitrile
Flow rate 1.0 to 1.5 mL/minute
Wavelength UV at 250 - 260 nm

EXAMPLES

The following non-limiting examples illustrate specific embodiments of the present invention. They are not intended to be limiting the scope of the present invention in any way.

Example 1: Preparation of compound of formula V

Compound of Formula I (100 gms) and acetic acid (20 mL) were added to methylene chloride (1500 mL) and the reaction mass was cooled to 0-10°C. Bromine (101.5 gms) was added in 3hrs at the same temperature and stirred for 1hr at 0-10°C. To the reaction mass was added triphosgene (117.8 gm) and sodium bicarbonate (277.8 gms) at 0-10°C. Reaction mass was heated to 25-35°C and stirred for 6 hrs at same temperature. After completion of the reaction, cooled the reaction mass to 0-10°C and added 40% aqueous monomethylamine (102.9 gm). Reaction mass was heated to 25-35°C and stir for 10 hrs at same temperature. After completion of the reaction, added water (1000 mL), product containing organic layer was separated and aqueous layer was extracted with methylene chloride (500 mL). The combined organic layer was concentrated under vacuum at below 50°C. O-xylene (750 mL) was added followed by sodium cyanide (42.1 gms), copper (I) iodide (18.9 gms) and N, N-dimethylethylene diamine (49.6 gms). Reaction mass was heated to 135-145°C and stirred for 6 hrs at same temperature. After completion of the reaction, the reaction mass was cool to 25-35°C, added water (1000 mL) and stirred at the same temperature for 4hrs. Filtered the solids, washed the wet cake with water (200 mL) followed by o-xylene (150 mL), and dried the wet material initially at 25-35°C for 1hr and then at 75-85°C for 8 hrs to obtain title compound. Yield: 102.7 gms; HPLC purity: 99.2%.

Example 2: Preparation of crystalline Form B of Cyantraniliprole

3-Bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylic acid (100 gms) and 2-amino-5-cyano-N, 3-dimethyl benzamide (compound V, 62.5 gms) were added to acetonitrile (300 ml) at room temperature and stirred for 10-15 min. 3-Picoline (80 gms) was added at 25-35°C, cooled to -5°C to 5°C and methanesulfonyl chloride (49.2 gms) was added. The temperature of the reaction mass was raised to 25-35°C and stirred for 2 hrs. The reaction mass was heated to 45-55°C and water (100 ml) was added. Stirred the mass at 45-55°C for 1 hr, cooled to 25-32°C and stirred for 1 hr. The reaction mass was filtered, washed with water (400 ml) and suck dried 15-30 min to get the title compound. Yield: 170 gms.

Example 3: Preparation of crystalline Form A of cyantraniliprole

The above obtained Cyantraniliprole (170 gms) was added to ethylbenzene (1000 ml) at room temperature. The reaction mass was heated to reflux and stirred for 3hrs at reflux while collecting water by azeotropic distillation. Cooled the temperature slowly to 25-35°C, stirred for 1 hr, filtered and washed with ethylbenzene (100 ml). Dried the material initially under vacuum at 25-35°C for 1 hr and then at 75-85°C under vacuum for 8 hrs to get the title compound. Yield= 130 gms. XRD as represented in figure 1.

Example 4: Preparation of crystalline Form A of cyantraniliprole

Wet Cyantraniliprole obtained in example 2 (170 gms) was added to n-propanol (2500 ml) at room temperature. The reaction mass was heated to 80-90°C and stirred for 15-30mins. Cooled the reaction mass temperature slowly to 25-35°C, stirred for 1 hr, filtered and washed with n-propanol (100 ml). Dried the material initially under vacuum at 25-35°C for 1 hr and then at 75-85°C under vacuum for 8 hrs to get the title compound. Yield= 129 gms. XRD as represented in figure 1.

It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the above description should not be constructed as limiting, but merely as exemplifications of preferred embodiments. For example, the functions described above and implemented as the best mode for operating the present invention are for illustration purposes only. Other arrangements and methods may be implemented by those skilled in the art without departing from the scope and spirit of this invention. Moreover, those skilled in the art will envision other modifications within the scope and spirit of the specification appended hereto.
,CLAIMS:WE CLAIM:

1. An improved process for preparation of compound of Formula V, comprising:

a) reacting a compound of Formula I with a source of bromide in a suitable solvent to obtain a compound of Formula II,

b) reacting the compound of Formula II with phosgene or its derivative and a suitable base to obtain a compound of Formula III,

c) reacting the compound of Formula III with a source of monomethyl amine to obtain a compound of Formula IV, and

d) reacting the compound of formula IV with cyanide sourceto obtain a compound of Formula V;
wherein the steps a) to d) are carried out in one-pot reaction.

2. The process as claimed in claim 1, wherein the source of bromine is selected from elemental bromine, sulfuryl bromide, N-bromosuccinimide, mixture of metal bromide-hydrogen peroxide in acid aqueous medium, mixture of hydrogen bromide-hydrogen peroxide, Metal bromide/metal periodate combination in acidic medium, m-chloroperbenzoic acid/ hydrogen bromide, acetyl bromide and 1,3-dibromo-5,5-dimethylhydantoin.

3. The process as claimed in claim 1, wherein the suitable solvent is selected from dimethylacetamide, dimethylformamide, N-methylpyrrolidone; ethyl acetate, methyl acetate; acetone, methyl isobutyl ketone, methyl ethyl ketone; acetonitrile, propionitrile; tetrahydrofuran, methyl tetrahydrofuran, dimethyl ether, diisopropyl ether, methyl tertiary butyl ether, 1,4-dioxane; methylene chloride, ethylene chloride, chloroform; toluene, xylene and mixture thereof.

4. The process as claimed in claim 1, wherein the phosgene or its derivative used in step b) is selected from the group consisting of phosgene, diphosgene, triphosgene and bromophosgene and wherein the suitable base is selected from lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium tert-butoxide, sodium carbonate, potassium carbonate, cesium carbonate, sodium bicarbonate, potassium bicarbonate, triethylamine, isopropyl ethylamine, diisopropyl amine, diisopropyl ethylamine, N-methyl morpholine, piperidine, 2-picoline, 3-picoline and mixtures thereof.

5. The process as claimed in claim 1, wherein the source of monomethyl amine is selected from aqueous methylamine, methylamine in solvent, methylamine gas.

6. The process as claimed in claim 1, wherein the cyanide source is selected from barium cyanide, calcium cyanide, copper cyanide, sodium cyanide, potassium cyanide, zinc cyanide, cesium cyanide, cobalt cyanide, ammonium cyanide, trimethylsilyl cyanide, potassium ferricyanide, sodium ferricyanide and mixtures thereof.

7. An improved process for preparation of compound of Formula V, comprising:
a) reacting a compound of Formula I with a source of bromide in a suitable solvent to obtain a reaction solution of compound of Formula II,
b) reacting the step a) solution of compound of Formula II with phosgene or its derivative and a suitable base to obtain a reaction solution of compound of Formula III,
c) reacting the step b) solution of compound of Formula III with a source of monomethyl amine,
d) optionally, removing the organic solvent,
e) optionally, adding an organic solvent to the step d) reaction mass,
f) treating step e) reaction mass with cyanide source to obtain a compound of Formula V, and
g) isolating the compound of Formula V.

8. The process as claimed in claim 7, wherein in the source of bromide is bromine; wherein in the phosgene or its derivative is triphosgene; wherein in the base is sodium bicarbonate; wherein in the source of monomethyl amine is aqueous methyl amine; wherein in the cyanide source is sodium cyanide; and wherein in the solvent is methylene chloride, xylene or mixtures thereof.

9. An improved process for preparation of crystalline Form A of cyantraniliprole, comprising:
a) providing cyantraniliprole in a suitable solvent or mixture of solvents,
b) heating the step a) reaction mixture to a temperature from about 50°C to reflux, and
c) isolating crystalline Form A of cyantraniliprole.

10. The process as claimed in claim 9, wherein in the suitable solvent is selected from ethyl benzene, methyl isobutyl ketone, methyl ethyl ketone, acetone, cyclopentylmethyl ether, 2-methyl tetrahydrofuran, dibutyl ether, methyl tert. butyl ether, 1,4-dioxane, acetonitrile, methanol, n-propanol, isopropanol, t-butanol, benzyl alcohol, ethyl acetate, n-propyl acetate, isopropyl acetate, cyclohexane, hexane, dichloromethane, dimethyl sulfoxide and mixtures thereof; and wherein step c) further comprises cooling the reaction mass to a temperature of about 35°C or less.