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: A process for preparation of Tri hydrolysis of Triclopyr-alkyl ester.
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.

A PROCESS FOR PREPARATION OF TRICLOPYR BY HYDROLYSIS OF TRICLOPYR-ALKYL ESTER
FIELD OF INVENTION
This invention relates to a process for preparation of triclopyr, by hydrolysis of triclopyr-alkyl ester.
BACKGROUND AND PRIOR ART
Triclopyr is a selective systemic herbicide which is used for control of broadleaf weeds and woody plants in grasslands, parklands, along rights-of-way, forests etc. It is used as ester or salt such as triclopyr butoxyethyi ester, triclopyr ethyl ester and triclopyr triethylammonium salt.
Cava et al. have reported preparation of triclopyr in only 17% yield by hydrolysis of its ethyl ester which was prepared from N2CHC02C2H5 and halogenated 2-pyridone [Journal of Organic Chemistry (1958), 23, 1614-16].
Dow Chemical Co. has reported in the patent US3862952, a process for preparation of triclopyr by treating 2,3,5,6-Tetrachloropyridine with paraformaldehyde in Me2SO containing KCN followed by hydrolysis to obtain triclopyr. Use of cyanide is a disadvantage of this method.

Oxidation of pyridine and quinoline bases and its use for the production of pyridinecarboxylic acids such as triclopyr has been reported in Chemicke Listy pro Vedu a Prumysl (1961), 55, 1199-209. This method involves an additional step involving oxidation of the pyridine base.
The inventors of present invention have developed a novel process for preparation of Triclopyr by hydrolysis of Triclopyr esters with improved yield and purity compared to the prior art processes.
OBJECTS OF INVENTION
It is an object of this invention to provide an efficient process for preparation of Triclopyr by hydrolysis of Triclopyr-alkyl esters.
Another object of invention is to provide a process for preparation of Triclopyr by hydrolysis of Triclopyr-alkyl ester with improved yield and purity compared to prior art process.
DETAILED DESCRIPTION OF INVENTION
As per an embodiment of the present invention, Triclopyr can be prepared by hydrolysis of its alkyl ester by heating the slurry of alkyl ester of Triclopyr with an alkali.
Though hydrolysis can be carried out in presence of any alkali, the preferred alkali is NaOH for convenience and economic reasons. Since it is inherent property of NaOH to absorb water and it has

tendency to partially convert into bicarbonate and carbonate when exposed to atmospheric C02, excess amount may be considered to compensate for the same.
The colour of the product is improved by adding an oxidizing agent such as NaOCl or H202. The oxidizing agent should be added after . cooling the reaction mass to room temperature.
Details of process for preparation of Triclopyr by hydrolysis of its alkyl esters is given hereunder.
Preparation of Triclopyr By Hydrolysis of Methyl Ester of Triclopyr:
Methyl ester of triclopyr was prepared by process disclosed in US3969360. Methyl ester was then hydrolyzed to Triclopyr by heating a slurry of said ester in water with an alkali, cooling the reaction mass to room temperature, adding NaOCl or H202 for oxidation of impurities and colour improvement, acidifying the mass with a mineral acid, e.g., sulfuric acid or an organic acid, e.g., acetic acid to pH 1-2 to obtain precipitate of the product, and filtration thereof.
As mentioned earlier, the color of the product is improved by adding a decolorising agent such as NaOCl or H202 (30%). The decolorising agent should be added after cooling the reaction mass to room temperature.

The product is finally precipitated by acidifying the reaction mass to pH 1-2 with a mineral acid like H2SO4 or an organic acid like acetic acid. The yield obtained is found to be better when a mineral acid is used.
The purity of the product obtained by this process is >98%.
EXAMPLE-1
In a reactor equipped with a mechanical stirrer, thermometer pocket and reflux condenser, 0.351 moles of triclopyr-methyl ester was taken. Water was added to make 10% aqueous slurry. 16.85 g (0.421 moles) of NaOH was added. The slurry was heated to 80-85°C for four hours. The reaction mass was then cooled to room temperature. 85 ml 4% NaOCl solution was added and mixture was stirred for 30 min. The reaction mass was then acidified to pH 1-2 with sulfuric acid to get white precipitate which was filtered and dried to obtain product in 94% yield.
EXAMPLES 2 8B 3
The process as described in Example-1 above was repeated except the molar ratio of triclopyr-methyl to NaOH was changed. The results are tabulated in the following Table.

Example No. Molar ratio (triclopyr-methyl ester:NaOH) Yield
1 1:1.2 94.00%
2 1:1.1 92.20%
3 1:1 89.90%
EXAMPLE-4
In a reactor equipped with a mechanical stirrer, thermometer pocket and reflux condenser, 0.351 moles of triclopyr-methyl ester was taken. Water was added to make 10% aqueous slurry. 16.85 g (0.421 moles) of NaOH was added. The slurry was heated to 80-85°C for four hours. The reaction mass was then cooled to room temperature. 70 ml H202 was added and mixture was stirred for 30 min. The reaction mass was then acidified to pH 1-2 with sulfuric acid to get white precipitate which was filtered and dried to obtain product in 94.2% yield.
EXAMPLES 5 & 6
The process as described in Example-4 above was repeated except the molar ratio of triclopyr to NaOH was changed. The results are tabulated in the following Table.

Example No. Molar ratio (triclopyr-methyl estenNaOH) Yield
4 1:1.2 94.20%
5 1:1.1 92.10%
6 1:1 89.78%

EXAMPLE-7
In a reactor equipped with a mechanical stirrer, thermometer pocket and reflux condenser, 0.351 moles of triclopyr-methyl ester was taken. Water was added to make 10% aqueous slurry. 16.85 g (0.421 moles) of NaOH was added. The slurry was heated to 80-85°C for four hours. The reaction mass was then cooled to room temperature. 85 ml 4% NaOCl solution was added and mixture was stirred for 30 min. The reaction mass was then acidified to pH 1-2 with acetic acid to get white precipitate which was filtered and dried to obtain product in 83% yield.
EXAMPLES 8 & 9
The process as described in Example-7 above was repeated except the molar ratio of triclopyr to NaOH was changed. The results are tabulated in the following Table.

Example No. Molar ratio
(triclopyr-methyl estenNaOH) Yield
7 1:1.2 83.00%
8 1:1.1 81.10%
9 1:1 79.90%
EXAMPLE-10
In a reactor equipped with a mechanical stirrer, thermometer pocket and reflux condenser, 0.351 moles of triclopyr-methyl ester was

taken. Water was added to make 10% aqueous slurry. 16.85 g (0.421 moles) of NaOH was added. The slurry was heated to 80-85°C for four hours. The reaction mass was then cooled to room temperature. 70 ml H202 was added and mixture was stirred for 30 min. The reaction mass was then acidified to pH 1-2 with acetic acid to get white precipitate which was filtered and dried to obtain product in 82.8% yield.
EXAMPLES 11 & 12
The process as described in Example-10 above was repeated except the molar ratio of triclopyr to NaOH was changed. The results are tabulated in the following Table.

Example No. Molar ratio
(triclopyr-methyl
ester:NaOH) Yield
10 1:1.2 82.8%
11 1:1.1 81.25%
12 1:1 79.75%
Preparation of Triclopyr By Hydrolysis of Ethyl Ester of Triclopyr:
Ethyl ester of triclopyr was prepared by process disclosed in US4701531. Ethyl ester was then hydrolyzed to Triclopyr by heating a slurry of said ester in water with an alkali, cooling the reaction mass to room temperature, adding NaOCl or H202 for oxidation of

impurities and colour improvement, acidifying the mass with a mineral acid e.g., sulfuric acid or an organic acid e.g., acetic acid to pH 1-2 to obtain precipitate of the product, and filtration thereof. The purity of the product obtained by this process is >98%.
EXAMPLE-13
In a reactor equipped with a mechanical stirrer, thermometer pocket and reflux condenser, 0.404 moles of triclopyr-ethyl ester was taken. Water was added to make 10% aqueous slurry. 19.42 g (0.485 moles) of NaOH was added. The slurry was heated to 80°C for 3.5 hours. The reaction mass was then cooled to room temperature. 115 ml 4% NaOCl solution was added and mixture was stirred for 30 min. The reaction mass was then acidified to pH 1-2 with sulfuric acid to get white precipitate which was filtered and dried to obtain product in 93% yield.
EXAMPLES 14 & 15
The process as described in Example-13 above was repeated except the molar ratio of triclopyr-ethyl to NaOH was changed. The results are tabulated in the following Table.

Example No. Molar ratio (triclopyr-ethyl estenNaOH) Yield
13 1:1.2 93.00%
14 1:1.1 91.20%
15 1:1 88.70%

EXAMPLE-16
In a reactor equipped with a mechanical stirrer, thermometer pocket and reflux condenser, 0.404 moles of triclopyr-ethyl ester was taken. Water was added to make 10% aqueous slurry. 19.42 g (0.485 moles) of NaOH was added. The slurry was heated to 80°C for 3.5 hours. The reaction mass was then cooled to room temperature. 95 ml H202 was added and mixture was stirred for 30 min. The reaction mass was then acidified to pH 1-2 with sulfuric acid to get white precipitate which was filtered and dried to obtain product in 92.5% yield.
EXAMPLES 17 & 18
The process as described in Example-16 above was repeated except the molar ratio of triclopyr-ethyl to NaOH was changed. The results are tabulated in the following Table.

Example No. Molar ratio (triclopyr-ethyl ester: NaOH) Yield
16 1:1.2 92.50%
17 1:1.1 91.00%
18 1:1 88.20%
EXAMPLE-19
In a reactor equipped with a mechanical stirrer, thermometer pocket and reflux condenser, 0.404 moles of triclopyr-ethyl ester was taken. Water was added to make 10% aqueous slurry. 19.42 g (0.485 moles) of NaOH was added. The slurry was heated to 80°C for 3.5

hours. The reaction mass was then cooled to room temperature. 115 ml 4% NaOCl solution was added and mixture was stirred for 30 min. The reaction mass was then acidified to pH 1-2 with acetic acid to get white precipitate which was filtered and dried to obtain product in 75% yield.
EXAMPLES 20 8B 21
The process as described in Example-19 above was repeated except the molar ratio of triclopyr-ethyl to NaOH was changed. The results are tabulated in the following Table.

Example No. Molar ratio (triclopyr-ethyi ester: NaOH) Yield
19 1:1.2 75.00%
20 1:1.1 72.50%
21 1:1 70.20%
EXAMPLE-22
In a reactor equipped with a mechanical stirrer, thermometer pocket and reflux condenser, 0.404 moles of triclopyr-ethyl ester was taken. Water was added to make 10% aqueous slurry. 19.42 g (0.485 moles) of NaOH was added. The slurry was heated to 80°C for 3.5 hours. The reaction mass was then cooled to room temperature. 95 ml H202 was added and mixture was stirred for 30 min. The reaction mass was then acidified to pH 1-2 with acetic acid to get white precipitate which was filtered and dried to obtain product in 74.45% yield.

EXAMPLES 23 & 24
The process as described in Example-22 above was repeated except the molar ratio of triclopyr-ethyl to NaOH was changed. The results are tabulated in the following Table.

Example No. Molar ratio (triclopyr-ethyl ester: NaOH) Yield
22 1:1.2 74.45%
23 1:1.1 72.10%
24 1:1 69.90%

CLAIMS:
1. A process for preparation of triclopyr by hydrolysis of triclopyr-
alkyl ester comprising steps including:
(i) heating an aqueous slurry of said ester with an alkali;
(ii) cooling the reaction mass to room temperature;
(iii) adding a decolorizing agent;
(iv) acidifying the reaction mass for precipitation of the product and
filtration thereof.
2. A process as claimed in claim-1, wherein the triclopyr-alkyl ester is C1-3 alkyl ester.
3. A process as claimed in any of the claims 1 or 2, wherein aqueous slurry of triclopyr-alkyl ester has a concentration in the range of 5-15 wt%.
4. A process as claimed in any of the claims 1-3, wherein the molar ratio of triclopyr-alkyl ester to alkali is 1 : (1-2).
5. A process as claimed in claim-1, wherein the decolorizing agent is NaOCl or H202.
6. A process as claimed in claim-1, wherein the reaction mass is
acidified to pH 1-2 for precipitation of the product.