FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See Section 10; Rule 13)
1. TITLE OF THE INVENTION:
IMPROVEMENTS IN THE PROCESS FOR PREPARATION OF FENPYROXIMATE
2. APPLICANT(S)
(a) NAME: Excel Crop Care Limited
(b) NATIONALITY: An Indian Company
(c) ADDRESS:
184-87, Swami Vivekanand Road, Jogeshwari(West), Mumbai 400 102, Maharashtra, India.
3. PREAMBLE TO THE DESCRIPTION:
The following COMPLETE specification particularly describes the nature of this invention and the manner in which it is to be performed.

IMPROVEMENTS IN THE PROCESS FOR PREPARATION OF FENPYROXIMATE
FIELD OF INVENTION
This invention relates to a process for preparation of a pyrazole acaricide viz. Fenpyroximate. More specifically, present invention relates to the preparation of Fenpyroximate by reaction of 4-chloromethylbenzoic acid t-butyl ester with l,3-dimethyl-5-phenoxypyrazole-4-oxime in aqueous medium in presence of a catalyst.
BACKGROUND AND PRIOR ART
Fenpyroximate is a broad-spectrum phenoxypyrazole acaricide effective against phytophagous mites on a variety of crops.
Synthesis of fenpyroximate by reaction of 4-chloromethylbenzoic acid t-butyl ester with l,3-dimethyl-5-phenoxypyrazole-4-oxime is reported by Hyun-Ja Park et al. in the Korean Journal of Pesticide Science, Vol.9, No.3, pp 274-277. This process uses DMSO as a solvent and KOH. In this process, it is necessary to partition reaction mixture with ethyl acetate and water. The organic phase is washed with brine and water, dried over Na2S04 and evaporated under reduced pressure to give the product in 79% yield. This process has disadvantages. It uses high-boiling DMSO as solvent and KOH which is comparatively expensive.
A process for preparation of fenpyroximate from 4-chloromethylbenzoic acid t-butyl ester and l,3-dimethyl-5-phenoxypyrazole-4-oxime is also reported in KR2002-73763. This process also uses DMSO. The yield obtained is 73.2% when KOH is used. However, the yield drops to 66% when NaOH is used.
It is desirable to obtain high yield but eliminate high-boiling organic solvent and use NaOH which is cheaper than KOH. Inventors of present invention have developed an improved process for preparation of fenpyroximate from 4-

chloromethylbenzoic acid t-butyl ester and l,3-dimethyl-5-phenoxypyrazole-4-oxime in aqueous medium using a catalyst.
OBJECTS OF INVENTION
The main object of present invention is to provide a process for preparation of fenpyroximate by reaction of 4-chloromethylbenzoic acid t-butyl ester with 1,3-dimethyl-5-phenoxypyrazole-4-oxime which obviates the need of carrying out the reaction in an organic solvent.
Another object of invention is to provide a process for preparation of fenpyroximate by reaction of 4-chloromethylbenzoic acid t-butyl ester with 1,3-dimethyl-5-phenoxypyrazole-4-oxime, which is cost-effective and environmentally friendly compared to the process reported in the prior art.
DETAILED DESCRIPTION OF THE INVENTION
l,3-Dimethyl-5-phenoxypyrazoIe-4-oxime reacts with 4-halomethylbenzoic acid tert-butyl ester in presence of an alkali to produce fenpyroximate. Inventors of the present invention have found that the reaction of l,3-Dimethyl-5-phenoxypyrazole-4-oxime with 4-halomethylbenzoic acid tert-butyl ester can be carried out without organic solvent, in presence of a catalyst viz., triethylbenzylammonium chloride, and NaOH. After completion of the reaction, as the reaction mass is sticky, methanol is added for separation of the product from the reaction mass. The yield obtained is comparable with that of the prior art wherein DMSO is used as a solvent. Present invention obviates the need of using solvent such as DMSO.
The inventors of present invention carried out various experiments involving reaction of 4-halomethylbenzoic acid tert-butyl ester and l,3-Dimethyl-5-phenoxypyrazoIe-4-oxime (with as well as without catalyst and/or organic solvent) to synthesize fenpyroximate.

Best results were obtained when the reaction was carried out in presence of catalyst without using organic solvent during course of the reaction. After completion of the reaction, methanol was added to facilitate separation of the product.
EXAMPLE-1
[This is a comparative example wherein the reaction is carried out in presence of methanol but without using catalyst]
In a 250 ml round bottom flask equipped with mechanical stirrer, thermometer and reflux condenser, 50 ml methanol and 3.8 gm (0.095 mole) sodium hydroxide were taken. The mixture was stirred to dissolve sodium hydroxide. 20 gm (0.0865 mole) l,3-Dimethyl-5-phenoxypyrazole-4-oxime was added and the reaction mixture was heated to 60°C for 2 hr. followed by cooling to room temperature. A solution of 25.86 gm (0.95 mole) 4-bromomethylbenzoic acid tert-butyl ester in 40 ml methanol was added to the mixture over a period of 1 hr. at 25-30°C. The reaction mass was heated to 60-62°C with constant stirring and was maintained at 60-62°C for 4 hrs. The reaction mass was then cooled to 10°C and filtered to obtain wet cake. The wet cake was dissolved in 60 ml methanol. 0.25 gm activated carbon was added and the mixture was heated to 63-65°C for 30 min. The solution was then filtered followed by cooling to room temperature. The reaction mass was filtered and product obtained was dried to get white powder of fenpyroximate in 60% yield with 92% purity.
EXAMPLE-2
This is a comparative example wherein the reaction is carried out in presence of methanol as well as catalyst.
In a 250 ml round bottom flask equipped with mechanical stirrer, thermometer and reflux condenser, 50 ml methanol, 20 gm (0.0865 mole) l,3-Dimethyl-5-phenoxypyrazole-4-oxime, 21.6 gm (0.0955 mole) 4-chloromethylbenzoic acid

tert-butyl ester and (0.008 mole) triethylbenzylammonium chloride (catalyst) were taken. The reaction mixture was stirred at 50-55°C for 30 min. 21 gm (0.13 mole) aqueous solution of sodium hydroxide was added over 1 hr. at 52-54°C. The reaction mass was maintained at 52-54°C for 4 hrs at pH 9.5-10. After completion of the reaction, the reaction mass was cooled to 10°G and filtered to obtain wet cake which was washed with water and dried to get light yellow 26.64 gm (0.063 mole) fenpyroximate in 73% yield and 93% purity.
EXAMPLE-3
This is a comparative example wherein the reaction is carried out in presence of methanol but without catalyst.
In a 250 ml round bottom flask equipped with mechanical stirrer, thermometer and reflux condenser, 50 ml methanol, 20 gm (0.0865 mole) l,3-Dimethyl-5-phenoxypyrazole-4-oxime and 21.6 gm (0.0955 mole) 4-chloromethylbenzoic acid tert-butyl ester. The reaction mixture was stirred at 50-55°C for 30 min. 21 gm (0.13 mole) aqueous solution of sodium hydroxide was added over 1 hr. at 52-54°C. The reaction mass was maintained at 52-54°C for 4 hrs at pH 9.5-10. After completion of the reaction, the reaction mass was cooled to 10°C and filtered to obtain wet cake which was washed with water and dried to get light yellow 25.54 gm (0.060 mole) fenpyroximate in 70% yield and 93% purity.
EXAMPLE-4
In this example, the reaction is carried out in presence of catalyst, without methanol. Methanol is added after reaction, to facilitate separation of the product.
In a 250 ml round bottom flask equipped with mechanical stirrer, thermometer and reflux condenser, 20 gm (0.0865 mole) l,3-Dimethyl-5-phenoxypyrazole-4-oxime, 16 gm (0.103 mole) aqueous solution of sodium hydroxide and 0.008 mole triethylbenzylammonium chloride (catalyst) were taken. The reaction mixture was stirred at 50-55°C for 30 min. 20.6 gm (0.091 mole) 4-

chloromethylbenzoic acid tert-butyl ester was added over a period of 1 hr. The reaction mass was cooked for 1 hr. at 50-55°C, followed by adding 50 ml methanol and stirring. The reaction mass was cooled to 10°C, filtered, washed with methanol and dried to get 29.19 gm (0.069 mole) white powder of fenpyroximate with 79% yield and 98% purity.

CLAIMS:
1. A process for preparation of fenpyroimate by reaction of l,3-Dimethyl-5-
phenoxypyrazole-4-oxime with 4-chloromethylbenzoic acid tert-butyl
ester in presence of an alkali and triethylbenzylammonium chloride as a
catalyst.
2. A process for preparation of fenpyroimate as claimed in claim 1, wherein the alkali used is sodium hydroxide.
3. A process for preparation of fenpyroimate as claimed in claim 1 or 2, wherein the reaction is carried out in an aqueous medium.
4. A process for preparation of fenpyroimate as claimed in any of the claims 1-3, comprising steps of (1) taking l,3-Dimethyl-5-phenoxypyrazole-4-oxime, aqueous NaOH and triethylbenzylammonium chloride catalyst in molar ratio of about 0.087:0.1:0.008 respectively in the reactor; (2) stirring the reaction mass at 50-55°C for 30 min.; (3) adding 4-chloromethylbenzoic acid tert-butyl ester 0.09 moles (proportionate to reactants mentioned in step 1) over a period of 1 hr.; (4) adding methanol and stirring (5) cooling the reaction mass, filtration and drying to obtain fenpyroximate.
5. A process for preparation of fenpyroimate as claimed in claim 4, wherein the fenpyroximate obtained in step 5 is washed with methanol and then dried.