Method for producing 2-cyanoacetic acid anhydride and further reaction products thereof

1. A process for producing 2-cyanoacetic acid anhydride, comprising the steps of:

a) preparing a reaction mixture, containing as reactants 2-cyanoacetic acid, and at least one C 4-20 carboxylic acid anhydride in at least one organic solvent, wherein the molar ratio of 2-cyanoacetic acid to C 4-20 carboxylic acid anhydride in said reaction mixture is greater than 1.5:1; and

b) subjecting the reaction mixture to a temperature of 0° C. to 100° C. to form 2-cyanoacetic acid anhydride.

2. The process of claim 1 , wherein the molar ratio of 2-cyanoacetic acid to C 4-20 carboxylic acid anhydride in said reaction mixture is from 2:1 to 3:1.

3. The process of claim 1 , wherein the C 4-20 carboxylic acid anhydride is a symmetrical C 4-20 carboxylic acid anhydride.

4. The process of claim 1 , wherein the C 4-20 carboxylic acid anhydride is selected from symmetrical carboxylic acid anhydrides of formula (I),

wherein R 1 represents C 1-9 -halogenoalkyl, or represents phenyl which is substituted by at least one substituent selected from fluorine, chlorine, bromine, cyano and/or nitro.

5. The process of claim 1 , wherein the C 4-20 carboxylic acid anhydride is selected from compounds of formula (III),

wherein each n, independently, is an integer from 1 to 5.

6. The process according to claim 1 , wherein the C 4-20 carboxylic acid anhydride is trifluoroacetic acid anhydride.

7. The process according to claim 1 , wherein the temperature in step b) is from 10° C. to 40° C.

8. The process of claim 1 , comprising the additional step c) of concentrating 2-cyanoacetic acid anhydride by removing at least a part of the organic solvent.

9. A process for producing 2-cyanoacetic acid esters, 2-cyanoacetic acid amides and/or 2-cyanoacetic acid thioesters, comprising the steps of:

i) carrying out a process of claim 1 to prepare a reaction mixture containing 2-cyanoacetic acid anhydride in an organic solvent;

ii) adding at least one reagent to the reaction mixture, wherein said reagent is selected from the group consisting of hydroxyl-containing compounds, amine-containing compounds, and thiol-containing compounds; and

iii) subjecting said mixture to a temperature of −20° C. to 80° C. to form 2-cyanoacetic acid esters, 2-cyanoacetic acid amides and/or 2-cyanoacetic acid thioesters.

10. The process of claim 9 , wherein the reagent is a monohydric or dihydric primary alcohol.

11. The process of claim 10 , wherein the monohydric or dihydric primary alcohol has general formula (II),

[HO—] n R 2   formula (II)

wherein n is 1 or 2 and R 2 stands for C 1-40 alkyl (for n=1), C 3-40 alkenyl (for n=1), C 3-40 cycloalkyl (for n=1), C 6-40 aryl (for n=1),

C 7-40 aralkyl (for n=1), C 2-40 alkoxyalkyl (for n=1), C 1-40 alkylene (for n=2), C 3-40 cycloalkylene (for n=2), or C 6-40 arylene (for n=2).

12. The process according to claim 9 , wherein the molar ratio of reagent to 2-cyanoacetic acid anhydride in step ii) is from 0.4:1 to 1.8:1.

13. The process according to claim 9 , wherein the at least one reagent is added in step ii) in the presence of at least one catalyst, wherein the catalyst is capable of catalyzing the formation of 2-cyanoacetic acid esters, 2-cyanoacetic acid amides and/or 2-cyanoacetic acid thioesters.

14. The process according to claim 9 , wherein the temperature in step iii) is from 0° C. to 40° C.

15. The process according to claim 1 , wherein the organic solvent is selected from ketones, esters, hydrocarbons, halogenated hydrocarbons, nitriles, amides and ethers.