The present invention relates to a process for the preparation of compounds of formula I
1
wherein the substituents are as defined in claim 1, by conversion of a compound of formula II
2
reaction of that compound with a compound of formula IV
X—C(O)—Q (IV)
wherein X is a leaving group, to form a compound of formula V
3
and treatment of that compound in the presence of a base with catalytic amounts of cyanide ions.