Title of Invention

"A PROCESS FOR PREPARATION OF DIFLUOROACETYL FLUORIDE AND ITS DERIVATIVES"

Abstract

The present invention relates to a novel process of preparation of difluoroacetyl fluoride and its derivatives from 1- alkoxy 1,1,2,2 tetrafluoroethane of the formula CHF2-CF2-O-R, wherein R is C1-4. In this process difluoroacetyl fluoride is obtained from 1- alkoxy, 1,1,2,2-tetrafluoroethane by vapour phase reaction over metal halide impregnated on carbon surface. The reaction requires less amount of catalyst. The process is cost effective and environment friendly. The present invention also relates to a method for conversion of difluoroacetyl fluoride into corresponding esters and amides, with subsequent treatment with alcohol and amine respectively.

Full Text

FIELD OF INVENTION; The present invention relates to the process of preparation of difluoroacetyi fluoride and its derivatives from 1- alkoxy 1,1,2,2 tetrafluoroethane of the formula CHF2-CF2-O-R, BACKGROUND OF INVENTION: Ditiuoroacetic acid derivatives like amides and esters are compounds which find applications as intermediates in pharamceutical and agrochemical industry. Various methods for the synthesis of these compounds have been described. Difluoroacetyi fluoride is synthesized by reacting 1 -alkoxy-1,1,2,2 tetrafluoroethane with sulfur trioxide and fluorosuifonic acid. (!Zh.Org.Chim,1971, 7,710-13). Although the process yields desired product, handling of hazardous and toxic by product & handling equally hazardous raw materials like fluorosuifonic acid and sulfur trioxide on a commercial scale and the waste effluent generated make the process problematic. US 4357282 refers to a process of synthesis of difluoroacetyi fluoride starting with 1-alkoxy-1,1,2,2-tetrafluoroethane in presence of antimony halide or titanium halide as a catalyst The catalyst required per mole of reactant is also Mgh i.e., 7-8 gram per mole of reactant. The preparation and handling of corrosive antimony halide catalyst makes the process difficult for the scale up. US 5710317 describes the process of synthesizing difluoroacetyi fluoride and its derivatives starting with 1 -alkoxy-1,1,2,2 tetrafluoroethane. The reaction is done in vapor phase over metal oxide catalyst. The process does not describe the physical texture & chemical nature of the catalyst which may have direct bearing on the performance of the catalyst. Further Catalyst is activated using chlorofluorocarbons which are ozone depleting materials. Esters of chlorodifluoroacetic acid is reduced with zinc to produce ditiuoroacetic acid ester (WO2005/085173). It is further known that the esters of difluoroacetic acid can also be prepared by treating difluoroacetic acid with alcohol in presence of mineral acids such as sulphuric acid or phosphoric acid. Both the above processes suffer from the drawback that the starting material chlorodifluoroacetic acid ester as well as difluoroacetic acid are readily not available. Further-, in case of reduction of chlorodifluoroacetic acid ester, the reaction generates zinc waste which needs to be addressed. Synthesis of esters of diffuoroacetic acid involving a reaction of l-alkoxy-1,1,2,2 tetrafluoroethane with sulfuric acid and silica is known (J.Am. Chem. Soc. 72, 1860 (1950). The drawback with the process is that the reaction needs to be carried out in a reactor out of exotic material of construction such as hastalloy or inconel which adds cost to the process. Now we have a process which overcomes the above drawbacks of the prior art. In this process difiuoroacetyi fluoride is obtained from 1- alkoxy,l.l,2,2-tetrafluoroethane by vapour phase reaction over metal halide impregnated on carbon surface. None of the method in the prior art discloses a process for preparation of difiuoroacetyi fluoride and its derivatives by the vapor phase reaction of l-alkoxy-1,1,2,2- tetrafluoroethane, in presence of a metal chloride catalyst impregnated on carbon surface. OBJECTIVES: It is an object of the present invention to provide a method for preparation of difiuoroacetyi fluoride and its derivatives by contacting l-alkoxy-1,1,2,2- tetrafluoroethane of the formula CHF2-CF2-O-R wherein R is C1-4, with a catalyst, wherein the catalyst is ferric chloride impregnated on carbon, in vapour phase. Further objective of the invention is to provide a method for conversion of difiuoroacetyi fluoride into corresponding esters and amides, with subsequent treatment with alcohol, and amine respectively. Yet another object of the present invention is to provide a process which is more environment friendly and requires less amount of catalyst when compared to those cited in the art,. Another object of the invention is to provide a cheaper catalyst amongst the various catalyst used in the vapor phase reaction which is commercially available. DETAILED DESCRIPTION OF THE INVENTION: 'The present invention relates to a process of preparing difuoroacetyl fluoride and its derivatives by catalytic vapor phase reaction of 1-alkoxy 1,1,2,2 tetrafluoroethane of the formula CHF2-CF2-O-R, wherein R is C1-4 with a catalyst, wherein the catalyst is ferric chloride impregnated on carbon, in vapour phase. In the present invention 1-alkoxy 1,1,2,2 tetrafluoroethane is subjected to vapor phase reaction in a reactor in presence of active Ferric chloride supported on carbon catalyst. The reaction is represented by the formula: CHF2-CF2-O-R —> HCF2COF + RF wherein R is C1-4. The catalyst employed in the catalytic vapor phase reaction is a metal chloride catalyst impregnated on the surface of carbon. The carbon for the catalyst is activated carbon from industrially applicable carbon source , The weight % of the ferric chloride impregnated on carbon is 2 to 40% of weight of said catalyst. The catalyst is in the form of pellets/granules. The catalyst required for the present invention is 0.5-2 gram per mole of the reactant, which is less than the catalyst required in the process in prior art. There is no pretreatment required for the catalyst except perhaps for moisture removal by passing an inert gas such as N2 at 100 to 250 degree C. for 24 hrs. The reaction is carried out in a reactor operated at a single temperature. Diethyl ether is preheated and passed as vapours onto the catalyst which is kept in a metal reactor tube. Reactor does not have zones with different temperatures. The material of construction of metal reactor tube can be stainless steel which is compatible with the catalyst. The catalyst is heated at a temperature of 80 to 250 degree C, preferably at 100 to 230 degree C, by an oil bath or heating tape with a temperature fluctuation of +/- 5 degree C. The reaction is carried out at a pressure of 1-5 bar . The contact time for the reactant on the said catalyst is in the range-of 3 to 20 seconds. The products formed are Difluoroacetyi fluoride and alkyl fluoride is a by-product. The yield of difluoroacetyi fluoride is 95 to 99%. The process is highly cost effective as the catalyst as FeCl3 is a cheap catalyst and is available commercially. The reaction of 1-alkoxy-1,1,2,2-tetrafluoroethane with the ferric chloride catalyst impregnated on the surface of carbon gives high yield and the output per se is higher. It is well known that the acid fluoride so formed can be converted into ester or amide in the solution phase or gas phase depending on the type of alcohol or amine used. Esters of Difluoroacetic acid are prepared by reacting difluoroacetyl fluoride obtained in the above process with alcohols, wherein the alcohol is selected from a group consisting of primary, secondary and tertiary alcohols with 1-4 carbon atoms. Amides of difluoroacetic acid can be prepared by reacting difluoroacetyl fiouride , with amine wherein the amine is selected from a group consisting of primary and secondary amines with 1-6 carbon atoms. The reaction for preparation of these derivatives is carried out at temperature ranging from -10 to 30 degree C at atmospheric, sub-atmospheric or high pressure. A tertiary amine or heterocyclic amine such as pyridine is added during the reaction, the product separates out as a bottom layer in case of ester, which can be washed with water and further purified by distillation. Amide can be obtained in similar manner. The whole process is cost effective and environment friendly. Now, the present invention will be described in further details with reference to Examples. However, it should be understood that the present invention is by no means restricted by such specific Examples. Example-1 Preparation of difluoro acetyl fluoride from 1-ethoxy 1,1,2,2 tetrafluoro ethane: A metal tube of diameter 1 cm was packed with 25 g FeC13 catalyst impregnated on carbon.33% fecl3 on carbon) This was connected to a steam of nitrogen and the tube heated to 230 degree C by means of a heating tape. After 2hrs, vapours of 1-alkoxy 1,1,2,2-tetrafiuoro ethane was passed alongwith inert gas such as nitrogen.. 100 g of the diethyl ether was passed over a period of 6 hrs. The effluent was connected to two traps immersed in acetone dry ice bath maintained at -30 degree C. The product collected in the trap weighed 65 grams which was analyzed by NMR as difluoroacetyl fluoride. The by product ethyl fluoride was collected and analyzed separate!}/. Example-2 Without change of catalyst and the condition of the reaction 500 grams of said ether was passed over the catalyst bed. The product formed was collected as in example-1. This was identified as Difluoroacetyl fluoride. The % yield was seen similar to example one. Example-3 Preparation of ethyl difluoroacetate in the absence of an amine: The acid fluoride which was obtained from Example-1 was passed into two ice cooled traps containing 31.5 grams of ethanol in each trap. After the reaction was over, the content of first trap was distilled to separate HF from ester. Contents of second trap were eventually transferred to the first trap. The product ester was confirmed as ethyl difluoroacetate. Example-4 Preparation of ethyl difluoroacetate in the presence of an amine: The same experiment as shown in Example-3 was repeated with two traps each containing 31.5 grams of ethanol and 54.10 grams of pyridine. After the reaction was over, the reaction mass in the first trap was washed with water and the organic layer separated. The product was finally distilled. This was analyzed and confirm as ethyl difluoroacetate. ExampIe-5 Preparation of Diethyl difluoroacetamide: The acid fluoride was obtained from Example-1 was passed into two ice cooled traps each containing 50 grams of diethyl amine and 54.10 grams of pyridine in a suitable solvent. The reaction mixture in the first trap was washed with water and the organic layer separated. The product was finally purified by distillation. It was confirmed as Diethyl difluoroacetamide. We Claim: 1. A process for preparation of difluoroacetyl fluoride and its derivatives which comprises contacting 1-alkoxy-1,1,2,2- tetrafluoroethane of the formula CHF2-CF2-O-R wherein R is C1-4, with a catalyst, wherein the catalyst is ferric chloride impregnated on carbon, in vapour phase. 2. A process for preparation of difluoroacetyl fluoride as claimed in claim 1, wherein the weight % of the ferric chloride impregnated on carbon is 2 to 40% of weight of said catalyst, 3. A process for preparation of difluoroacetyl fluoride as claimed in claim L wherein the carbon for the catalyst is selected from a group of graphite, activated carbon and carbon carrier. 4. A process for preparation of difluoroacetyl fluoride as claimed in claim 1, wherein the said catalyst is preheated at a temperature of 80 to 250 degree C; and pretreated by passing N2 at a temperature followed by fluorination at a temperature ranging from 150 to 250 degree C. 5. A process for preparation of difluoroacetyl fluoride as claimed in claim 1, wherein 1-alkoxy-1,1,2,2 tetrafluoroethane is contacted on the said catalyst for 3-20 second to produce difluoroacetyl fluoride, 6. A process for preparation of difluoroacetyl fluoride as claimed in claim 1, wherein the catalyst is 0.5-2 g per mole of the reactant. 7. A process for preparation of difluoroacetyl fluoride as claimed in claim I, wherein 1-alkoxy-1,1,2,2 tetrafluoroethane is contacted with; the said catalyst at a temperature ranging from 80 to 250 degree centigrade, preferably at 100 to 230 degree C. 8. A process for preparation of difluoroacetyl fluoride as claimed in claim. 1, wherein the reaction is carried out at a pressure range of 1-5 bar. 9. A process for preparation of difluoroacetic acid esters comprising of reacting difluoroacetyl fiouride of claim 1, with alcohols, wherein the alcohol is selected from a group consisting of primary, secondary and tertiary alcohols with 1-4 carbon atoms. 10. A process for preparation of difluoroacetic acid amides comprising; of reacting difluoroacetyl fiouride of claim 1, with amine wherein the amine is selected from a group consisting of primary and secondary amines with 1-6 carbon atoms. 11. A process for preparation of difluoroacetyl fluoride amides and alcohols comprising of reacting difluoroacetyl fiouride of claim. 1, with amine and alcohol, wherein the amine is selected from a group consisting of primary and secondary amines with 1-6 carbon atoms; and wherein the alcohol is selected from a group consisting of primary, secondary and tertiary alcohols with 1-4 carbon atoms. 12. A process for preparation of difluoroacetyl fluoride esters and amides as claimed in claim 10 and 11, wherein the reaction is carried out in presence of tertiary amine or heterocyclic amine like pyridine. 13. A process for preparation of difluoroacetyl fluoride esters and/or amides as claimed in claim 9 to 11, wherein reaction is carried out in a temperature range of -10 to 30 degree C at atmospheric, sub-atmospheric or high pressure. 14. A process for preparation of difluoroacetyl fluoride substantially as hereinbefore described with reference to the foregoing examples. 15. A process for preparation of difluoroacetyl fluoride esters substantially as hereinbefore described with reference to the foregoing examples. 16. A process for preparation of difluoroacetyl fluoride amides substantially as hereinbefore described with reference to the foregoing examples.

Documents:

1161-del-2008-abstract.pdf

1161-del-2008-Claims-(05-09-2014).pdf

1161-del-2008-Claims-(08-05-2013).pdf

1161-del-2008-Claims-(31-03-2014).pdf

1161-del-2008-claims.pdf

1161-del-2008-Correspondence Others-(02-09-2014).pdf

1161-del-2008-Correspondence Others-(03-07-2014).pdf

1161-del-2008-Correspondence Others-(05-09-2014).pdf

1161-del-2008-Correspondence Others-(07-01-2014).pdf

1161-del-2008-Correspondence Others-(31-03-2014).pdf

1161-del-2008-Correspondence-Others-(08-05-2013).pdf

1161-del-2008-correspondence-others.pdf

1161-del-2008-description (complete).pdf

1161-del-2008-form-1.pdf

1161-del-2008-form-2.pdf

1161-del-2008-form-3.pdf

1161-del-2008-form-5.pdf

1161-del-2008-GPA-(05-09-2014).pdf

1161-del-2008-GPA-(31-03-2014).pdf