Description:
FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)

“AN IMPROVED PROCESS FOR CHLORINATION OF METHYLPYRIDINES”
This patent application is an improvement over the invention filed in earlier Indian Patent Application No. IN201811010381, filed by the same applicant.

SRF LIMITED, AN INDIAN COMPANY,
SECTOR 45, BLOCK-C, UNICREST BUILDING,
GURGAON – 122003,
HARYANA (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 an improved process for producing trichloromethyl pyridines selectively by reacting methylpyridines with 1-chloropyrrolidine-2,5-dione in presence of radical initiator.

BACKGROUND OF THE INVENTION
Trichloromethyl pyridines are used as an intermediate for medicines, agricultural chemicals and dyes especially herbicides.
Ttrichloromethyl pyridines can be prepared by rapidly mixing in the vapor phase, chlorine, an appropriate methylpyridine compound in an inert diluent and subjecting the mixture to temperatures of about 400-490°C or 240-270°C. The desired products can then be distilled from the resulting product stream.
U.S. Patent no. 3,412,095 discloses a vapor phase chlorination of 4-picoline at a temperature in the range of 230-260ºC using steam as inert medium and with a contact time of 3.8 seconds to give 4-trichloromethylpyridine.
Indian Patent Application No. 201811010381 filed by the present applicant discloses a vapour phase chlorination of picolines to generate chlorinated trichloromethylpyridines. The vapour phase chlorination of methylpyridine initiates ring as well as side chain chlorination, resulting in mono and di-chlorinated trichloromethylpyridines, which are difficult to separate from the desired trichloropyridine.
It has been observed that methylpyridines can be selectively chlorinated using 1-chloropyrrolidine-2,5-dione in presence of a radical initiator to give trichloropyridines in good yield.

OBJECT OF THE INVENTION
The main object of the present invention is to provide a simple, cost effective and an industrially applicable and a selective process for preparation of trichloromethyl pyridines.

SUMMARY OF THE INVENTION
The present invention provides a process for preparation of trichloromethylpyridine, comprising the step of treating methylpyridine with 1-chloropyrrolidine-2,5-dione in presence of a radical initiator.

DETAILED DESCRIPTION OF THE INVENTION
As used herein, the methylpyridine includes substituted or unsubstituted methylpyridines selected from a group consisting of 2-methylpyridine; 3-methylpyridine and 4-methylpyridine or the like.
As used herein, the trichloromethylpyridines, includes substituted or unsubstituted trichloromethylpyridines selected from a group consisting of 2-trichloromethylpyridine; 3-trichloromethylpyridine and 4-trichloromethylpyridine or the like
In an embodiment, the present invention provides a process for preparation of trichloromethylpyridine, comprising the step of treating methylpyridine with 1-chloropyrrolidine-2,5-dione at a temperature in the range of 60 to 140oC.
In another embodiment, the present invention provides a process for preparation of trichloromethylpyridine, comprising the step of treating methylpyridine with 1-chloropyrrolidine-2,5-dione at a temperature in the range of 60 to 90oC.

In an embodiment of the present invention, 1-chloropyrrolidine-2,5-dione is used in the range of 3 to 6 mole equivalent with respect to the methylpyridine.
In an embodiment, the present invention provides a process for preparation of trichloromethylpyridine, comprising the step of treating methylpyridine with 1-chloropyrrolidine-2,5-dione in presence of a radical initiator selected from a group consisting of UV light, azobisisobutyronitrile, 4'-azobis(4-cyanopentanoic acid), di-tert-butyl peroxide, benzoyl peroxide and methyl ethyl ketone peroxide or the like.
In another embodiment, the process of present invention is carried out in a non-polar solvent selected from a group consisting of halogenated aliphatic and aromatic solvent such as bromodichloromethane, dibromochloromethane, trichlorofluoromethane, dichloromethane, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, trichloroethylene, tetrachloroethylene, 1,2-dichloropropane, trans-1,3-dichloropropylene, bis(chloro)methyl ether, bis(2-chloroethyl)ether, bis(2-chloroisopropyl)ether, 2-chloroethylvinyl ether, chlorobenzene, o-chlorobenzene, m-chlorobenzene, trichloroacetonitrile, chloroform, carbon tetrachloride, trichloroethane, 1,1,1,2-tetrachloroethane and 1,1,2,2-tetrachloroethane.
In another embodiment, the process of present invention selectively provides trichloromethylpyridine of purity 98-99.9%.
In another embodiment, the process of present invention selectively provides trichloromethylpyridines, substantially free of ring chlorinated impurities.
As used herein, the term substantially free of ring chlorinated impurities refers to less than 1% of ring chlorinated impurities, preferably ring chlorinated impurities in the range of 0.01-1%.
As used herein, the ring chlorinated impurities, includes chlorinated trichloromethylpyridines selected from a group consisting of 3-chloro-2-trichloromethylpyridine; 4-chloro-2-trichloromethylpyridine; 5-chloro-2-trichloromethylpyridine; 6-chloro-2-trichloromethylpyridine; 2-chloro-3-trichloromethylpyridine; 4-chloro-3-trichloromethylpyridine; 5-chloro-3-trichloromethylpyridine; 6-chloro-3-trichloromethylpyridine; 2-chloro-4-trichloromethylpyridine; 3-chloro-4-trichloromethylpyridine; 6-chloro-4-trichloromethylpyridine; 4,6-dichloro-2-trichloromethylpyridine; 2,6-dichloro-3-trichloromethylpyridine; 2,6-dichloro-4-trichloromethylpyridine; 4-chloromethlpyridie and 4-dichloromethyl pyridine or the like.
The trichloromethylpyridines may be isolated by using techniques known in the art for example distillation, extraction, evaporation, column chromatography and layer separation or a combination thereof.
Embodiments of the invention are not mutually exclusive but may be implemented in various combinations. The described embodiments of the invention and the disclosed examples are given for the purpose of illustration rather than limitation of the invention as set forth in the appended claims.
The completion of the reaction can be monitored by any one of chromatographic techniques such as thin layer chromatography (TLC), high pressure liquid chromatography (HPLC), ultra-pressure liquid chromatography (UPLC), Gas chromatography (GC) and alike.
The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention.

EXAMPLES
Example 1: Process for preparing 2-trichloromethylpyridine
1-Chloropyrrolidine-2,5-dione (857g; 6.42 mol) was added to a mixture of 2-methylpyridine (100g; 1.07 mol) and azobisisobutyronitrile (1.76g; 0.01 mol) in carbon tetrachloride in a reactor and the reaction mass was heated upto 80-85°C. The progress of reaction was monitored by GC analysis. After completion of the reaction, the reaction mass was cooled and filtered. The filtrate organic mass was washed with sodium bicarbonate solution (10%, 1000g), dried and distilled to obtain the titled product.
Analysis: Yield: 70%; Purity: 98% (by GC); chlorinated 2-trichloromethylpyridine: 0.01%
Example 2: Process for preparing 3-trichloromethylpyridine
The process of Example 1 was repeated by using 3-methylpyridine as reactant to obtain the following results:
Analysis: Yield: 75%; Purity (by GC): 99.1%; chlorinated 3-trichloromethylpyridine: 0.01%
Example 3: Process for preparing 4-trichloromethylpyridine
The process of Example 1 was repeated by using 4-methylpyridine as reactant to obtain the following results:
Analysis: Yield: 72%; Purity (by GC): 98.5%; chlorinated 4-trichloromethylpyridine: 0.02%
It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention and specific examples provided herein without departing from the spirit and scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention that come within the scope of any claims and their equivalents.
, C , Claims:
WE CLAIM:
1. A process for preparation of trichloromethylpyridine, comprising the step of treating methylpyridine with 1-chloropyrrolidine-2,5-dione in presence of a radical initiator.
2. The process as claimed in claim 1, wherein methylpyridine is treated with 1-chloropyrrolidine-2,5-dione at a temperature in the range of 60-140°C.
3. The process as claimed in claim 1, wherein 1-chloropyrrolidine-2,5-dione is used in the range of 3 to 6 mole equivalent with respect to the methylpyridine.
4. The process as claimed in claim 1, wherein the radical initiator is selected from a group consisting of UV light, azobisisobutyronitrile, 4'-azobis(4-cyanopentanoic acid), di-tert-butyl peroxide, benzoyl peroxide and methyl ethyl ketone peroxide.
5. The process as claimed in claim 1, wherein the process is carried out in a non-polar solvent selected from a group consisting of halogenated aliphatic and aromatic solvent, bromodichloromethane, dibromochloromethane, trichlorofluoromethane, dichloromethane, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, trichloroethylene, tetrachloroethylene, 1,2-dichloropropane, trans-1,3-dichloropropylene, bis(chloro)methyl ether, bis(2-chloroethyl)ether, bis(2-chloroisopropyl)ether, 2-chloroethylvinyl ether, chlorobenzene, o-chlorobenzene, m-chlorobenzene, trichloroacetonitrile, chloroform, carbon tetrachloride, trichloroethane, 1,1,1,2-tetrachloroethane and 1,1,2,2-tetrachloroethane.

6. The process as claimed in claim 1, wherein the trichloromethylpyridine is obtained with a purity in the range of 98-99.9%.
7. The process as claimed in claim 1, wherein the trichloromethylpyridine is obtained with ring chlorinated impurities in the range of 0.01-1%.

Dated this 31st day of October 2022.