Indian Patents. 263726:" A PROCESS FOR PREPARATION OF CHLORODIFLUROCETONITRILE"

Title of Invention	" A PROCESS FOR PREPARATION OF CHLORODIFLUROCETONITRILE"
Abstract	The invention relates to a process for preparation of chlorodifluoroacetonitrile. The process involves contacting chlorodifluoroacetamide with trifluoroacetic anhydride in presence of an organic base. The reaction is generally carried at atmospheric temperature and pressure conditions.

Full Text	Field of invention The present invention relates to a process used for preparation of chlorodifluoroacetonitrile by dehydration of chlorodifluoroacetamide in presence of a dehydrating agent like trifluoroacetic anhydride and triethyl amine, chlorodifluoroacetonitrile is a compound used in various synthesis of agrochemicals. One such use is the preparation of thiazole derivatives that are useful as fungicides and insecticide. Background of art:- Various methods for synthesis of chloro difluoro acetonirile are known in art. US 2745867 describes the process of synthesizing chloro difluoro acetonirile by vapour phase reaction of trichloro acetonitrile with anhydrous hydrogen fluoride over chromia catalyst. The process is conducted at high temperature of 450 degree C and calls for exotic material of construction of equipment in addition to capital cost involved in the pheripherialia. In addition the process has a drawback of generating mixture of acetonitriles which needs to be separated from low boiling hydrogen chloride. The catalyst chromia has a definite life and has to be disposed in an environmental friendly manner which adds cost to the overall process. US patent number 2939878 describes a process for preparation of fluoronitriles, especially chlorodifluoroacetomtriles by reacting cyanogen chloride with difluoromethane or chloro difluoro methane. The process suffers from the drawback that cyanogen chloride is not freely available and the reaction calls for very harsh temperature condition of 650-750 degree C. Further the yield of the process is only 51.5 mole percent which makes the process commercially unattractive. In general, the preparation of nitrile by dehydration of carboxamides is very well documented. Amides have been converted to nitriles with basic reagents, however such conversion needs harsh & drastic condition for the carrying the transformation. On the other hand acidic reagents appears to offer milder conditions and better yields. Some of the common acidic reagents used are trichloroacetyl chloride, thionyl chloride, phoshoryl chloride/ pyridine, trifluoroacetic anhydride/pyridine, triphenyl phosphine ditriflate, aluminum chloride and vilsmerier reagent Although there are number of dehydrating agent which could be used for transforming chlorodifluoroacetamides to chloro fluoro acetonitrile, generally they have drawbacks such as unsatisfactory yield, harsh and vigorous reaction conditions or difficult work up process, environmental concerns etc. In some cases the reagent used is so specific that it is difficult to employ them on a commercial scale. This invention relates to an operationally simple and high yielding procedure for conversion of chlorodifluoroacetamide to corresponding nitrile using trifluoroacetic anhydride in presence of trithylamine or pyridine. Moreover, the by product of the process is trifluoroacetic acid. TFA is a reagent used frequently in organic synthesis because of a combination of convenient properties: volatility, solubility in organic solvents, and its strength. It is also less oxidizing than sulfuric acid but more readily available in anhydrous form than hydrochloric acid. One complication to its use is that TFA forms an azeotrope with water with a boiling point of 105 °C. It is also used as a ion pairing agent in liquid chromatography for separation of organic compounds, particularly peptides and small proteins. It is a versatile solvent for NMR spectroscopy (for materials stable in acid). The derived acid anhydride, trifluoroacetic anhydride (TFAA), [CF3C(0)]20, is a common reagent for introducing the trifluoracetyl group. Therefore, there exists a need for a process which is free of the above drawbacks and could be scaled up on a commercial level. The objective of the present invention is to provide a process for preparation of chloro difluoro acetaonitrile without the use of catalyst, which could operate at atmospheric condition thereby bringing huge saving on the energy cost. Another objective of the present invention is to provide a process where both trifluoroacetic acid and triethyl amine can be recovered and reused and as such no waste is generated in the process. SUMMARY OF THE INVENTION: The process of current invention involves contacting chlorodifluoroacetamide with trifluoroacetic anhydride in presence of an organic base selected from triethylamine and pyridine. The reaction is generally carried at atmospheric temperature and pressure conditions. More particularly the reaction is carried between the temperature -15 degree C to + 50 degree C. STATEMENT OF INVENTION: The present invention provides a process for preparation of chlorodifluoroacetonitnle comprising reacting chlorodifluoroacetamide with a dehydrating agent in presence of an organic base. The present invention also provides a process wherein trifluoroacetic acid obtained after the dehydration reaction is recycled back to reactor. DESCRIPTION: The present invention discloses a process for conversion of chlorodifluoroacetamide into chlorodifluoroacetonitnle by reaction with a dehydrating agent in presence of an organic base. The dehydrating agent can be for example an anhydride of the kind of trifluoroacetic anhydride and acetic anhydride, preferably trifluoroacetic anhydride.The process of current invention involves contacting chlorodifluoroacetamide with trifluoroacetic anhydride in presence of an organic base selected from triethylamine and pyridine. The reaction is generally carried at atmospheric temperature and pressure conditions. More particularly the reaction is carried between the temperature -15 degree C to + 50 degree C. An organic base is typically a tertiary amine, in particular a trialkylamine, e.g. triethylamine, tributylamine or ethyl diisopropylamine; or a heterocyclic amine such as pyridine and its methyl derivatives like lutidine or collidine; preferably triethylamine. The stoichiometric ratio of chlorodifluoroacetamide to dehydrating agent may vary 1:1 to 1:4. However it is preferred to carry the reaction in a molar ratio between 1:1 to 1: 1.5. The molar ratio of chlorodifluoroacetamide to trifluoroacetic anhydride may vary 1:1 to 1:4. However it is preferred to carry the reaction in a molar ratio between 1:1 to 1: 1.5. The stoichiometric ratio of dehydrating agent to organic base for the process is between 1:1.2 to 1:5. More favorably, the preferred molar ratio of trifluoroacetic anhydride to triethyl amine or pyridine is between 1:1. 2 to 1: 2.5. The reaction is conducted at -15 degree C to +50 degree C at normal atmospheric pressure conditions, preferably at 5 to 15 degree C. After the reaction, reaction mass is allowed to warm to the atmospheric condition and is stirred to assure the completion of the reaction. The gaseous chlorodifluoroacetonitrile is trapped in a cold trap. In a preferred embodiment the byproduct i.e. trifluoroacetic acid can be recycled back to the reactor, in which dehydration takes place, for better efficiency. The excellent yield and the very mild reaction conditions, demonstrates the usefulness and the versatility of this novel process for synthesizing chlorodifluoroacetonitrile. The present invention may be further illustrated, but is not to be construed as limited by the following examples : Example 1 Pyridine 137 gram was added drop wise to stirred ice cooled solution suspension of 70 grams chlorodifluoroacetamide in 165 grams of trifluoroacetic anhydride. The rate of addition was controlled such that the reaction mass temperature remained below 5- 10 degree C. The reaction mass was allowed to warm to the atmospheric condition and was stirred for a period of 2 hours. The gaseous chlorodifluoroacetonitrile was trapped in a cold trap maintained at -70 degree C. Quantity of material collected in the trap was 47.94 amounting to 79.59 % yield. The purity of the chlorodifluoroacetonitrile was checked by gas chromatograph and was seen at 98 %. The pyridine & trifluoroacetic acid from the reaction pot was recovered and recycled by a process known in the art. Example -2. Using the methodology similar to the example -1, 65.3 grams of chlorodifluoroacetamide was added to 152.3 grams of Trifluoroacetic anhydride. Pyridine 103 grams was added slowly to the reaction pot maintaining a temperature of 15 degree C. The reaction mass was allowed to warm to the atmospheric condition and was stirred for a period of 2 hours. From the reaction pot, 44.14 grams of chloro difluoro acetontrile was collected into a pressure cylinder maintained at -70 degree C. The yield based on the quantity collected is 78.55 %. The purity of the chlorodifluoroacetonitrile was analyzed by gas chromatograph to be 98.9 %. Example 3. 65.1 gram of chlorodifluoroacetamide was mixed with 155 grams of trifluoroacetic anhydride and the reaction mass was cooled to 10-15 degree C. Triethyl amine was added drop by drop to the reaction mass maintaining the requisite temperature. After addition is over the mass was stirred for further a period of 3 hrs. The gaseous chlorodifluoroacetonitrile leaving the reactor was condensed and collected in pressure cylinder. The quantity of material collected is 45.2 grams resulting in a yield of 80.22 %. The triethyl amine and trifluoroacetic acid from the reaction pot was recovered and recycled for further batches. We Claim: 1. A process for preparation of chlorodifluoroacetonitrile comprising reacting chlorodifluoroacetamide with a dehydrating agent in presence of an organic base. 2. A process as claimed in claim 1, wherein the dehydrating agent is selected from trifluoroacetic anhydride and acetic anhydride. 3. A process as claimed in any of the preceding claims, wherein the dehydrating agent is trifluroacetic anhydride. 4. A process as claimed in any of the preceding claims, wherein the organic base is selected from a group consisting of a tertiary amine of the kind of triethylamine, tributylamine, ethyl diisopropylamine and a heterocyclic amine such as pyridine and its methyl derivatives like lutidine or collidine. 5. A process as claimed in any of the preceding claims, wherein the organic base is preferably triethylamine. 6. A process as claimed in any of the preceding claims, wherein the stoichiometric ratio of chlorodifluoroacetamide to dehydrating agent is from 1:1 to 1:4. 7. A process as claimed in any of the preceding claims, wherein the stoichiometric ratio of chlorodifluoroacetamide to dehydrating agent is from 1:1 to 1: 1.5. 8. A process as claimed in any of the preceding claims, wherein the stoichiometric ratio of dehydrating agent to organic base for the process is between 1:1.2 to 1:5. 9. A process as claimed in any of the preceding claims, wherein the stoichiometric ratio of dehydrating agent to organic base for the process is between 1:1.2 to 1: 1.25. 10. A process as claimed in any of the preceding claims, wherein the reaction is carried out at a temperature of -15 degree C to +50 degree C at normal atmospheric pressure conditions. 11. A process as claimed in any of the preceding claims, wherein the reaction is carried out at a temperature of 5 degree C to 15 degree C at normal atmospheric pressure. 12. A process as claimed in any of the preceding claims, wherein the reaction of chlorodifluoroacetonitrile with a dehydrating agent in presence of an organic base produces trifluoroacetic acid as a by product, which is recycled back into the reaction mixture. 13. A process for preparation of chlorodifluoroacetonitrile substantially hereinbefore described with reference to foregoing examples.

Full Text

Field of invention
The present invention relates to a process used for preparation of chlorodifluoroacetonitrile by dehydration of chlorodifluoroacetamide in presence of a dehydrating agent like trifluoroacetic anhydride and triethyl amine, chlorodifluoroacetonitrile is a compound used in various synthesis of agrochemicals. One such use is the preparation of thiazole derivatives that are useful as fungicides and insecticide.
Background of art:-
Various methods for synthesis of chloro difluoro acetonirile are known in art.
US 2745867 describes the process of synthesizing chloro difluoro acetonirile by vapour phase reaction
of trichloro acetonitrile with anhydrous hydrogen fluoride over chromia catalyst. The process is
conducted at high temperature of 450 degree C and calls for exotic material of construction of
equipment in addition to capital cost involved in the pheripherialia. In addition the process has a
drawback of generating mixture of acetonitriles which needs to be separated from low boiling
hydrogen chloride.
The catalyst chromia has a definite life and has to be disposed in an environmental friendly manner
which adds cost to the overall process.
US patent number 2939878 describes a process for preparation of fluoronitriles, especially chlorodifluoroacetomtriles by reacting cyanogen chloride with difluoromethane or chloro difluoro methane. The process suffers from the drawback that cyanogen chloride is not freely available and the reaction calls for very harsh temperature condition of 650-750 degree C. Further the yield of the process is only 51.5 mole percent which makes the process commercially unattractive.
In general, the preparation of nitrile by dehydration of carboxamides is very well documented. Amides have been converted to nitriles with basic reagents, however such conversion needs harsh & drastic condition for the carrying the transformation. On the other hand acidic reagents appears to offer milder conditions and better yields. Some of the common acidic reagents used are trichloroacetyl chloride, thionyl chloride, phoshoryl chloride/ pyridine, trifluoroacetic anhydride/pyridine, triphenyl phosphine ditriflate, aluminum chloride and vilsmerier reagent
Although there are number of dehydrating agent which could be used for transforming
chlorodifluoroacetamides to chloro fluoro acetonitrile, generally they have drawbacks such as
unsatisfactory yield, harsh and vigorous reaction conditions or difficult work up process,
environmental concerns etc. In some cases the reagent used is so specific that it is difficult to employ
them on a commercial scale.
This invention relates to an operationally simple and high yielding procedure for conversion of
chlorodifluoroacetamide to corresponding nitrile using trifluoroacetic anhydride in presence of
trithylamine or pyridine.
Moreover, the by product of the process is trifluoroacetic acid. TFA is a reagent used frequently in
organic synthesis because of a combination of convenient properties: volatility, solubility in organic
solvents, and its strength. It is also less oxidizing than sulfuric acid but more readily available in
anhydrous form than hydrochloric acid. One complication to its use is that TFA forms an azeotrope
with water with a boiling point of 105 °C.
It is also used as a ion pairing agent in liquid chromatography for separation of organic compounds, particularly peptides and small proteins. It is a versatile solvent for NMR spectroscopy (for materials stable in acid).
The derived acid anhydride, trifluoroacetic anhydride (TFAA), [CF3C(0)]20, is a common reagent for
introducing the trifluoracetyl group.
Therefore, there exists a need for a process which is free of the above drawbacks and could be scaled
up on a commercial level.
The objective of the present invention is to provide a process for preparation of chloro difluoro acetaonitrile without the use of catalyst, which could operate at atmospheric condition thereby bringing huge saving on the energy cost.
Another objective of the present invention is to provide a process where both trifluoroacetic acid and triethyl amine can be recovered and reused and as such no waste is generated in the process.
SUMMARY OF THE INVENTION:
The process of current invention involves contacting chlorodifluoroacetamide with trifluoroacetic anhydride in presence of an organic base selected from triethylamine and pyridine. The reaction is generally carried at atmospheric temperature and pressure conditions. More particularly the reaction is carried between the temperature -15 degree C to + 50 degree C.
STATEMENT OF INVENTION:
The present invention provides a process for preparation of chlorodifluoroacetonitnle comprising reacting chlorodifluoroacetamide with a dehydrating agent in presence of an organic base.
The present invention also provides a process wherein trifluoroacetic acid obtained after the dehydration reaction is recycled back to reactor.
DESCRIPTION:
The present invention discloses a process for conversion of chlorodifluoroacetamide into
chlorodifluoroacetonitnle by reaction with a dehydrating agent in presence of an organic base.
The dehydrating agent can be for example an anhydride of the kind of trifluoroacetic anhydride and
acetic anhydride, preferably trifluoroacetic anhydride.The process of current invention involves
contacting chlorodifluoroacetamide with trifluoroacetic anhydride in presence of an organic base
selected from triethylamine and pyridine. The reaction is generally carried at atmospheric temperature
and pressure conditions. More particularly the reaction is carried between the temperature -15 degree C
to + 50 degree C.
An organic base is typically a tertiary amine, in particular a trialkylamine, e.g. triethylamine,
tributylamine or ethyl diisopropylamine; or a heterocyclic amine such as pyridine and its methyl
derivatives like lutidine or collidine; preferably triethylamine.
The stoichiometric ratio of chlorodifluoroacetamide to dehydrating agent may vary 1:1 to 1:4.
However it is preferred to carry the reaction in a molar ratio between 1:1 to 1: 1.5. The molar ratio of
chlorodifluoroacetamide to trifluoroacetic anhydride may vary 1:1 to 1:4. However it is preferred to
carry the reaction in a molar ratio between 1:1 to 1: 1.5.
The stoichiometric ratio of dehydrating agent to organic base for the process is between 1:1.2 to 1:5.
More favorably, the preferred molar ratio of trifluoroacetic anhydride to triethyl amine or pyridine is
between 1:1. 2 to 1: 2.5.
The reaction is conducted at -15 degree C to +50 degree C at normal atmospheric pressure conditions,
preferably at 5 to 15 degree C. After the reaction, reaction mass is allowed to warm to the atmospheric
condition and is stirred to assure the completion of the reaction. The gaseous chlorodifluoroacetonitrile
is trapped in a cold trap.
In a preferred embodiment the byproduct i.e. trifluoroacetic acid can be recycled back to the reactor, in
which dehydration takes place, for better efficiency.
The excellent yield and the very mild reaction conditions, demonstrates the usefulness and the
versatility of this novel process for synthesizing chlorodifluoroacetonitrile.
The present invention may be further illustrated, but is not to be construed as limited by the following
examples :
Example 1
Pyridine 137 gram was added drop wise to stirred ice cooled solution suspension of 70 grams
chlorodifluoroacetamide in 165 grams of trifluoroacetic anhydride. The rate of addition was controlled
such that the reaction mass temperature remained below 5- 10 degree C.
The reaction mass was allowed to warm to the atmospheric condition and was stirred for a period of 2
hours. The gaseous chlorodifluoroacetonitrile was trapped in a cold trap maintained at -70 degree C.
Quantity of material collected in the trap was 47.94 amounting to 79.59 % yield. The purity of the
chlorodifluoroacetonitrile was checked by gas chromatograph and was seen at 98 %.
The pyridine & trifluoroacetic acid from the reaction pot was recovered and recycled by a process
known in the art.
Example -2.
Using the methodology similar to the example -1, 65.3 grams of chlorodifluoroacetamide was added to
152.3 grams of Trifluoroacetic anhydride. Pyridine 103 grams was added slowly to the reaction pot
maintaining a temperature of 15 degree C. The reaction mass was allowed to warm to the atmospheric
condition and was stirred for a period of 2 hours.
From the reaction pot, 44.14 grams of chloro difluoro acetontrile was collected into a pressure cylinder
maintained at -70 degree C. The yield based on the quantity collected is 78.55 %. The purity of the
chlorodifluoroacetonitrile was analyzed by gas chromatograph to be 98.9 %.
Example 3.
65.1 gram of chlorodifluoroacetamide was mixed with 155 grams of trifluoroacetic anhydride and the
reaction mass was cooled to 10-15 degree C. Triethyl amine was added drop by drop to the reaction mass maintaining the requisite temperature. After addition is over the mass was stirred for further a period of 3 hrs. The gaseous chlorodifluoroacetonitrile leaving the reactor was condensed and collected in pressure cylinder.
The quantity of material collected is 45.2 grams resulting in a yield of 80.22 %. The triethyl amine and trifluoroacetic acid from the reaction pot was recovered and recycled for further batches.

We Claim:
1. A process for preparation of chlorodifluoroacetonitrile comprising reacting chlorodifluoroacetamide with a dehydrating agent in presence of an organic base.
2. A process as claimed in claim 1, wherein the dehydrating agent is selected from trifluoroacetic anhydride and acetic anhydride.
3. A process as claimed in any of the preceding claims, wherein the dehydrating agent is
trifluroacetic anhydride.
4. A process as claimed in any of the preceding claims, wherein the organic base is selected from a group consisting of a tertiary amine of the kind of triethylamine, tributylamine, ethyl diisopropylamine and a heterocyclic amine such as pyridine and its methyl derivatives like lutidine or collidine.
5. A process as claimed in any of the preceding claims, wherein the organic base is preferably triethylamine.
6. A process as claimed in any of the preceding claims, wherein the stoichiometric ratio of chlorodifluoroacetamide to dehydrating agent is from 1:1 to 1:4.
7. A process as claimed in any of the preceding claims, wherein the stoichiometric ratio of chlorodifluoroacetamide to dehydrating agent is from 1:1 to 1: 1.5.
8. A process as claimed in any of the preceding claims, wherein the stoichiometric ratio of
dehydrating agent to organic base for the process is between 1:1.2 to 1:5.
9. A process as claimed in any of the preceding claims, wherein the stoichiometric ratio of dehydrating agent to organic base for the process is between 1:1.2 to 1: 1.25.
10. A process as claimed in any of the preceding claims, wherein the reaction is carried out at a temperature of -15 degree C to +50 degree C at normal atmospheric pressure conditions.
11. A process as claimed in any of the preceding claims, wherein the reaction is carried out at a temperature of 5 degree C to 15 degree C at normal atmospheric pressure.
12. A process as claimed in any of the preceding claims, wherein the reaction of chlorodifluoroacetonitrile with a dehydrating agent in presence of an organic base produces trifluoroacetic acid as a by product, which is recycled back into the reaction mixture.
13. A process for preparation of chlorodifluoroacetonitrile substantially hereinbefore described with reference to foregoing examples.

Documents:

23-del-2009-Abstract-(18-11-2013).pdf

23-del-2009-abstract.pdf

23-del-2009-Claims-(12-05-2014).pdf

23-del-2009-Claims-(18-11-2013).pdf

23-del-2009-claims.pdf

23-del-2009-Correspondence Others-(12-05-2014).pdf

23-del-2009-Correspondence Others-(18-11-2013).pdf

23-del-2009-Correspondence Others-(26-06-2013).pdf

23-del-2009-correspondence-others.pdf

23-del-2009-Description (Complete)-(18-11-2013).pdf

23-del-2009-description (complete).pdf

23-del-2009-form-1.pdf

23-del-2009-form-2.pdf

23-del-2009-form-3.pdf

23-del-2009-form-5.pdf

23-del-2009-form-9.pdf

23-del-2009-GPA-(12-05-2014).pdf

23-del-2009-GPA-(18-11-2013).pdf

23-del-2009-GPA-(26-06-2013).pdf

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Patent Number

263726

Indian Patent Application Number

23/DEL/2009

PG Journal Number

47/2014

Publication Date

21-Nov-2014

Grant Date

17-Nov-2014

Date of Filing

07-Jan-2009

Name of Patentee

SRF LIMITED

Applicant Address

BOCK-C,SECTOR 45, UNICREST BUILDING,GURGAON,HARYANA,INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	IYENGAR,SARATHY	SRF LIMITED,BOCK-C,SECTOR 45, UNICREST BUILDING,GURGAON,HARYANA,INDIA
2	SAXENA,RAHUL	SRF LIMITED,BOCK-C,SECTOR 45, UNICREST BUILDING,GURGAON,HARYANA,INDIA
3	BALAJI,PRABU	SRF LIMITED,BOCK-C,SECTOR 45, UNICREST BUILDING,GURGAON,HARYANA,INDIA
4	ANAND,RAJDEEP	SRF LIMITED,BOCK-C,SECTOR 45, UNICREST BUILDING,GURGAON,HARYANA,INDIA

PCT International Classification Number

C07C51/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA