A process for the preparation of a compound according to claim 1 of formula I, or one of the E/Z isomers or tautomers thereof, in free form or in salt form, which process comprises:a) for the preparation of a compound of formula I wherein Y is OR1 and Z is O, either reacting a compound of formula ##STR28## wherein X, R1, R3, R4 and R9 are as defined for formula I, and X1 is a leaving group, option