| abstract |
The invention relates to a process for the preparation of a compound of formula (I) wherein the substituents are defined as in claim 1, which process comprises adding a compound of formula (II), wherein R 1 , R 2 and R 3 have the meanings as described under formula (I), in the presence of an inert organic solvent, to a mixture comprising an organic nitrite of formula (III) R4—O—N═O, wherein R 4 is C 1 -C 8 alkyl, a compound of formula (IV), and an inert organic solvent. |