Process for the preparation of acyl cyanide compounds

This invention relates to a new process for the preparation of acyl cyanides of the general formula R1-CO-CN (I) wherein R1 is an optionally substituted alkyl radical up to 18 carbon atoms, an optionally substituted cycloalkyl radical with 3 to 12 carbon atoms, an optionally substituted aryl radical or an optionally substituted 5- or 6-membered heterocyclic radical, which can additionally also be fused with a benzene ring, which process comprises reacting a carboxylic acid anhydride of the formula R1-CO-O-CO-R1 (II) with an alpha-hydroxynitrile of the formula (III) in which R2 and R3 are identical or different and represent a hydrogen atom, an optionally substituted alkyl radical with 1 to 18 carbon atoms, an optionally substituted cycloalkyl radical with 3 to 12 carbon atoms, an optionally substituted aryl radical or an optionally substituted 5- or 6-membered heterocyclic radical, which can additionally also be fused with a benzene ring. The acyl cyanides (I) are known compounds and can be used as starting material for the synthesis of herbicides.