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: Preparation of Triclopyr-Butoxyethyl ester by trans-esterification from Triclopyr-alkyl esters
2. APPLICANT(S)
(a) NAME: Excel Crop Care Limited
(b) NATIONALITY: An Indian Company
(c) ADDRESS:
184-87, Swami Vivekanand Road, Jogeshwari, Mumbai 400 102, Maharashtra. India.
(a) NAME: C.C. Shroff Research Institute
(b) NATIONALITY:
(c) ADDRESS:
13/14 Aradhana Industrial Development Corporation Near Virwani Industrial Estate Goregaon (East), Mumbai 400 063, Maharashtra. India
(a) NAME: Aimco Pesticides Limited
(b) NATIONALITY: An Indian Company
(c) ADDRESS:
"Akhand Jyoti", 8th Road, Santa Cruz (East), Mumbai - 400005, 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.

Preparation of Triclopyr-Butoxyethyl ester by trans-esterification from Triclopyr-alky! esters
FIELD OF INVENTION
The present invention relates to a process for preparation of triclopyr-butoxyethyl ester by trans-esterification from triclopyr-C1-3 alkyl ester. More particularly, the present invention relates to a process for preparation of triclopyt-butoxyethyl ester by trans-esterification from triclopyr-C1-3 alkyl ester
BACKGROUND AND PRIOR ART
A method for preparation of triclopyr-butoxyethyl ester has been reported in an Indian patent 197707 wherein triclopyr-butoxyethyl ester is obtained in 82% yield and 92% purity by reacting sodium 3,5,6-trichloropyridinate with 2-butoxyethyl chloroacetate in a solvent medium in presence of a phase transfer catalyst, removing solvent by distillation and distilling triclopyr butoxyethyl ester under vacuum. The method requires distillation of not only solvent, but also the product to achieve the desired purity of the product.
The inventors of present invention have developed a process which overcomes abovementioned disadvantages of the prior art as the process of present invention does not require a solvent for carrying out the reaction and provides improved yield and purity.

OBJECTS OF INVENTION
The object of present invention is to provide an efficient process for preparation of triclopyr-butoxyethyl ester by trans-esterification from triclopyr-C1-3-alkyl ester.
Another object of invention is to provide a process for preparation of triclopyr-butoxyethyl ester which does not require solvent for carrying out the reaction.
Yet another object of invention is to provide a process for preparation of triclopyr-butoxyethyl ester with improved yield and purity.
DETAILED DESCRIPTION OF INVENTION
A process has been developed for preparation of triclopyr-butoxyethyl ester. As per said process, Triclopyr-butoxyethyl ester is prepared by transesterification from triclopyr-C1-3-alkyl ester by heating a mixture of triclopyr- C1-3-alkyl ester with 2-butoxyethanol in presence of a catalyst. Preparation by transesterification from ethyl- or methyl ester is preferable due to commercial reasons.
The catalysts used in the process include titanium n-butoxide, methane sulfonic acid, p-toluene sulfonic acid and sulfuric acid.
Preparation of Triclopyr-Butoxyethyl ester by transesterification from Triclopyr-Ethyl ester:

As per said process, Triclopyr-butoxyethyl ester is prepared by transesterification from triclopyr-ethyl ester by heating a mixture of triclopyr-ethyl ester with 2-butoxyethanol in presence of a catalyst. Ethanol fromed during the reaction is distilled out simultaneously. Excess of 2-butoxyethanol is also removed by distillation. The catalyst is removed by washing the reaction mass with water. Small fraction of the product dissolved during water-washing is recovered by back extraction with ethylene dichloride. Ethylene dichloride is then removed by distillation under vacuum to obtain triclopyr-butoxyethyl ester with 95-97% purity.
EXAMPLE-1
In a 250 ml 3-necked round bottom flask equipped with a magnetic stirrer and connected to a distillation set up, 0.253 moles of 2-butoxyethanol was taken. It was heated to 90°C. 0.168 moles of triclopyr-ethyl ester was added with stirring maintaining the temperature at 90°C to form a clear solution. The mixture was heated to 120°C and 1 ml of titanium butoxide catalyst was added. Ethanol formed during trans-esterification was distilled out under vacuum. The temperature of the reaction mass was increased to 150°C. After 7 hrs., the reaction mass was analyzed and 92% conversion was observed. Excess of 2-butoxyethanol was removed by distillation. The reaction mixture was poured in water to remove catalyst. Some product dissolved in water washings was recovered by back-extraction with 100 ml ethylene dichloride which was dried over anhydrous sodium sulfate and solvent was removed by

distillation to obtain Triclopyr-butoxyethyl ester with 85.35% recovery.
EXAMPLE-2
The process as described in Example-1 above was repeated except the catalyst used was 1-ml of methanesulfonic acid. Triciopyr-butoxyethyl ester obtained with 87.85% yield and 96% purity.
EXAMPLE-3
The process as described in Example-1 above was repeated except the catalyst used was 1 g of p-toluenesulfonic acid. Triciopyr-butoxyethyl ester obtained with 90.3% yield and 97% purity.
EXAMPLE-4
The process as described in Example-1 above was repeated except the catalyst used was 1-ml of sulfuric acid. Triciopyr-butoxyethyl ester obtained with 82.10% yield and 84.7% purity.
Preparation of Triclopyr-Butoxyethyl ester by transesterification from Triclopyr-Methyl ester:
EXAMPLE-5
In a 250 ml 3-necked round bottom flask equipped with a magnetic stirrer and connected to a distillation set up, 0.554 moles of 2-butoxyethanol was taken. It was heated to 90°C. 0.364 moles of

triclopyr-methyl ester was added with stirring maintaining the temperature at 90°C to form a clear solution. The mixture was heated to 120°C and 1 ml of titanium butoxide catalyst was added. Methanol formed during trans-esterification was distilled out under vacuum. The temperature of the reaction mass was increased to 150°C. After 7 hrs., the reaction mass was analyzed and 98% conversion was observed. Excess of 2-butoxyethanol was removed by distillation. The reaction mixture was poured in water to remove catalyst. Some product dissolved in water washings was recovered by back-extraction with 100 ml ethylene dichloride which was dried over anhydrous sodium sulfate and solvent was removed by distillation to obtain Triclopyr-butoxyethyl ester with 96% yield and 98.5% purity.
EXAMPLE-6
The process as described in Example-5 above was repeated except the catalyst used was 1-ml of methanesulfonic acid. Triclopyr-butoxyethyl ester obtained with 96.6% yield and 98.8% purity.
EXAMPLE-7
The process as described in Example-5 above was repeated except the catalyst used was 1 g of p-toluenesulfonic acid. Triclopyr-butoxyethyl ester obtained with 96.2% yield and 98.6% purity.

EXAMPLE-8
In a reactor equipped with a mechanical stirrer, thermometer pocket, dean & stark and reflux condenser, 0.554 moles of 2-butoxyethanol was taken. It was heated to 90°C. 0.364 moles of triclopyr-methyl ester was added with stirring maintaining the temperature at 90°C to form a clear solution. The mixture was heated to 125°C and 1 ml of titanium butoxide catalyst was added. Methanol formed during trans-esterification was distilled out under vacuum. The temperature of the reaction mass was increased to 145°C. After 7 hrs., the reaction mass was analyzed and 98.5% conversion was observed. Excess of 2-butoxyethanol was removed by distillation at higher vacuum. The crude product Triclopyr-butoxyethyl ester was distilled under vacuum to obtain 95% yield and 99.25% purity of the product.
EXAMPLE-9
The process as described in Example-8 above was repeated except the catalyst used was 1-ml of sulfuric acid. Triclopyr-butoxyethyl ester obtained with 81.84% yield and 84.25% purity.
EXAMPLE-10
The process as described in Example-8 above was repeated except the catalyst used was 1-ml of methanesulfonic acid. Triclopyr-butoxyethyl ester obtained with 94.5% yield and 99% purity.

EXAMPLE-11
The process as described in Example-8 above was repeated except the catalyst used was 1 g of p-toluenesulfonic acid. Triclopyr-butoxyethyl ester obtained with 95.5% yield and 99.3% purity.

CLAIMS:
1. A process for preparation of triclopyr-butoxyethyl ester by
transesterification from triclopyr-C1-3-alkyl ester by heating a mixture
of triclopyr-C1-3-alkyl ester with 2-butoxyethanol in presence of
titanium n-butoxide as a catalyst.
2. A process as claimed in claim 1, except that the catalyst used is methanesulfonic acid.
3. A process as claimed in claim 1, except that the catalyst used is p-toluenesulfonic acid.

4. A process as claimed in claim 1, except that the catalyst used is sulfuric acid.
5. A process as claimed in any of the claims 1-4, wherein the molar ratio of triclopyr-alkyl ester to 2-butoxyethanol is 1 : (1-2).
6. A process as claimed in claim 5, wherein the catalyst is used in the range of 0.5 - 5.0 mole% based on the moles of triclopyr alkyl ester.
7. A process as claimed in any of the claims 1-6, wherein triclopyr-
butoxyethyl ester is obtained by:
(i) heating 2-butoxyethanol to 85- 120°C; (ii) adding triclopyr-alkyl ester and stirring; (iii) adding catalyst and stirring at 120-160°C;

(iv) removing alkanol formed during reaction by simultaneous distillation under reduced pressure;
(v) removing unreacted/excess 2-butoxyethanol by distillation under reduced pressure;
(vi) washing reaction mass with water to remove catalyst and allowing aqueous and organic phases to separate; (vii) back-extracting the fraction of product dissolved in water-washing; (viii) removing the solvent by distillation under reduced pressure.