Patent ID: 6911547

Claim:
A process for the preparation of a compound of formula I wherein R 1 , R 2 , R 3 and R 4 are each independently of the others hydrogen, C 1 -C 4 alkyl, halogen, hydroxy, C 1 -C 4 alkoxy, C 1 -C 4 alkoxycarbonyl, hydroxycarbonyl or cyano; A and E are each independently of the other C 1 -C 2 alkylene, which may be substituted once or up to four times by a C 1 -C 4 alkyl group or by halogen, hydroxy, C 1 -C 4 alkoxy, C 1 -C 4 alkoxy-carbonyl or cyano, and M+ is an alkali metal ion, alkaline earth metal ion or ammonium ion, which comprises a) reacting a compound of formula II wherein R 1 , R 2 , R 3 , R 4 , A and E are as defined for formula I, in the presence of an oxidising agent, to form a compound of formula III wherein R 1 , R 2 , R 3 , R 4 , A and E are as defined for formula I, and b) then converting that compound to a salt of formula I either in the presence of a base and a catalytic amount of a cyanide or in the presence of an alkali metal alcoholate or alkaline earth metal alcoholate or a hydroxide.