Claims:WE CLAIM:

1. A process for the preparation of Chlorantraniliprole of Formula-I,

by reacting a compound of Formula-II,

with a monomethylamine in the presence of iodine in a suitable solvent to obtain Chlorantraniliprole of Formula-I.
2. The process as claimed in claim 1, wherein the suitable solvent used in the reaction step is selected from alcohol, ketone and ether solvents or mixture thereof.
3. The process as claimed in claim 1, wherein the ether solvents is selected from dimethyl ether, diethyl ether, tetrahydrofuran (THF) and dioxane or mixtures thereof.
, Description:Field of the Invention
The present invention relates to a novel process for the preparation of Chlorantraniliprole of Formula-I.

Background of the Invention
Anthranilamide derivatives are a kind of novel insecticides with high efficacy and safety. 3-Bromo-N-(4-chloro-2-methyl-6-(methylcarbamoyl)phenyl)-1-(3-chloro-2-pyridyl)-1H-pyrazole-5-carboxamide is highly effective against insects, which is commercialized by DuPont, its generic common name is Chlorantraniliprole of formula-I.

There are a number of methods reported for preparing Chlorantraniliprole, for example:
WO03/015519 A1 and Bioorganic & Medicinal Chemistry Letters, 17 (2007), 6274-6279 disclose that 3-bromo-1-(3-chloro-2-pyridyl)-1H-pyrazole-5-carboxylic acid reacts with substituted anthranilic acid in the presence of methanesulfonyl chloride and pyridine to give the benzoxazinone in 86%-92% yield. Then the product reacts with the methylamine to yield the Chlorantraniliprole of Formula-I. Calculated by 3-bromo-1-(3-chloro-2-pyridyl)-1H-pyrazole-5-carboxylic acid, the overall yield of the two-steps is 58%-65%. The synthetic scheme is depicted in below Scheme-I.
Scheme-I
The disadvantageous of the above process are involving two step process from the two advanced intermediates. And the process involved usage of excess amount of expensive reagent methanesulfonyl chloride 3.0 to 5.2 mole equivalents and usage of expensive solvent like acetonitrile. The overall yield of the two-steps is 58%-65%. Therefore, this process is not suitable for commercial scale.

In another patent application, WO 2003016300 A1 first discloses a 3-Bromo-N-(4-chloro-2-methyl-6-(acetyl)phenyl)-1-(3-chloro-2-pyridyl)-1H-pyrazole-5-carboxamide of Formula-II. WO ‘300 also discloses a general process for the preparation of 3-Bromo-N-(4-chloro-2-methyl-6-(acetyl)phenyl)-1-(3-chloro-2-pyridyl)-1H-pyrazole-5-carboxamide of Formula-II by condensation of 2-amino-5-chloro-3-methylphenyl)-ethanone with 3-bromo-1-(3-chloro-2-pyridyl)-1H-pyrazole-5-carboxylic acid chloride in the presence of acid scavenger to give the compound of Formula-II. The synthetic scheme is depicted in below Scheme-II.

Scheme-II
WO ‘300 also discloses an alternate process for the preparation of Compound of Formula-II, According to the general process, 1-(2-Amino-5-chloro-3-methylphenyl)-ethanone is condensed with 3-bromo-1-(3-chloro-2-pyridyl)-1H-pyrazole-5-carboxylic acid in the presence of Dicyclohexylcarbodiimide (DCC) as dehydrating agent to give the compound of Formula-II. The synthetic scheme is depicted in below scheme-III.
Scheme-III
However, preparation of chlorantraniliprole using compound of Formula II is not reported in any literature.
In another patent application, WO2006/062978A1 discloses a process for the preparation of Chlorantraniliprole by reacting 3-bromo-1-(3-chloro-2-pyridyl)-1H-pyrazole-5-carboxylic with substituted aminobenzamide in the presence of methanesulfonyl chloride and 3-picoline. The yield of the product is 88.4% after purified by recrystallization. The synthetic scheme is depicted in below Scheme-IV.
Scheme-IV

The disadvantageous of the above process are usage of expensive reagent methanesulfonyl chloride and purity of compound is not mentioned.

Objective of the Invention

The main objective of the present invention is to provide a simple and cost effective process for the preparation of Chlorantraniliprole of Formula-I with high purity and good yield on a commercial scale.

Summary of the Invention
The present invention relates to a novel process for the preparation of Chlorantraniliprole of Formula-I,

by reacting a compound of Formula-II,

with a monomethylamine in the presence of iodine in a suitable solvent to obtain Chlorantraniliprole of Formula-I.

Detailed Description of the Invention
In one of the embodiment, the present invention provides a novel process for the preparation of Chlorantraniliprole of Formula-I by reacting compound of Formula-II with a monomethylamine in the presence of iodine in a suitable solvent to obtain Chlorantraniliprole of Formula-I.
The suitable solvent used in the above reaction step is selected from Alcohol such as methanol, ethanol, propanol, isopropanol and n-butanol, isobutanol and tert-butanol and/or mixture thereof; keto solvents such as acetone, diethyl ketone, ethyl methyl ketone and/or mixture thereof; and ether solvents such as dimethyl ether, diethyl ether and tetrahydrofuran (THF) and dioxane and/or mixture thereof, preferably tetrahydrofuran (THF).
The mole equivalents of monomethylamine used in above reaction step are 1.0 to 4.0, preferably 1.5 to 4 mole equivalents and more preferably 2 to 2.5 mole equivalents with respective compound of Formula-II.
The above reaction may be performed from 15°C to 100oC for 5 minutes to 2 hours, preferably 60-70°C for 1 hour.

Another embodiment of the present invention relates to a process for the preparation of compound of Formula-II from four steps, which is depicted in below Scheme-V.
Scheme-V
A compound of Formula-III undergoes acylation reaction in the presence of aluminium chloride, borontrichloride and acetonitrile to produce compound of Formula-IV, which is further reacted with maleic anhydride followed by esterification with methanol to produce compound of Formula-V. Further, compound of Formula-V is reacted with substituted pyridine compound to produce Compound of Formula-VI, which undergoes oxidation followed by bromination to produce Compound of Formula-II.
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.
EXAMPLES:

1) Preparation of compound of Formula-IV:
4-Chloro 2-methyl aniline (compound of Formula-IV, 5.0g, 1.0 mole equivalent) and toluene (30.0 ml) were charged into 500.0 ml 4NRBF under nitrogen atmosphere at 25-300C. Acetonitrile (0.74g, 0.51 mole equivalents) added to the mass (Clear solution observed). Reaction mass was cooled to 50C and BCl3 1M in methylene chloride (18.0 ml, 0.51 mole equivalents) was slowly added to the reaction mass through syringe. Reaction mass was allowed to room temperature and maintained for 1 h. Again reaction mass was cooled to 50C and AlCl3 (2.40 g, 0.51 mole equivalents) was added in two lots. Temperature was raised to reflux and maintained for 5 h for reaction completion.

Reaction mass was cooled to 50C, then 2N Aq.hydrochloric acid (35.0 ml) was added dropwise to the reaction mass. Then the resulting reaction mass was heated to reflux and maintained for 2.5 h. After completion of maintenance, reaction mass was cooled to 25-300C and extracted with ethyl acetate (3 x 50.0 ml). Layers were separated, combined organic layer was washed with water (2 x 50.0 ml) followed by saturated sodium chloride solution (50.0 ml). Organic layer was separated and dried over sodium sulphate. Solvent was distilled off under reduced pressure at 600C to obtain yellow coloured crystalline solid. Weight of the solid is 1.5 g (23.0% by theory).

2) Preparation of compound of Formula-V:
Compound of Formula-IV (2.0 g, 1.0 mole equivalent) and Toluene (20.0 ml) were charged into 100.0 ml 4NRB Flask under nitrogen atmosphere at 25-300C. To the reaction mass maleic anhydride (1.1g, 1.0 mole equivalent) was charged and the reaction mass was stirred for 10h at reflux temperature for reaction completion. Solvent was distilled off under reduced pressure to give crude acid compound.
The resulting crude was dissolved in methanol (50.0 ml) and was added conc. sulphuric acid (0.53g, 0.5 mole equivalents) and refluxed for 6h under stirring. After reaction completion, solvent was distilled off and the resulting crude was dissolved in ethyl acetate and washed with water (2x25 ml). Organic layer was dried over sodium sulphate and solvent was distilled off to afford compound of Formula-V.

3) Preparation of Chlorantraniliprole of Formula-I.
Compound of Formula-II (0.2 g, 1.0 mole equivalent) and tetrahydrofuran (10.0 ml) were charged into 100.0 ml 4NRB Flask under nitrogen atmosphere at 25-300C. After 5 min stirring, iodine (0.325g, 3.0 mole equivalents) and monomethylamine solution 2.0 M in tetrahydrofuran (2.13 ml, 0.132g, 10.0 mole equivalents) were charged to the reaction mass. Then the reaction mass was heated to 60-700C for 1h for reaction completion. Solvent was distilled off from the reaction mass to get crude. The resulting crude was subjected to recrystallization to obtain pure Chlorantraniliprole of Formula-I. Yield: 1.6 g (80%)

Alternatively, the chlorantraniliprole is made from using iodine, monomethylamine in tetrahydrofuran under pressure conditions in a sealed tube.