Patent ID: 7893270

Claim:
A process for the preparation of a compound of formula I wherein Y is an organic substituent which is so selected that the compound of formula I has a pK value of from 1 to 5; A 1 is CR 1 R 2 ; A 2 is oxygen, C(O), SO 2 or (CR 3 R 4 ) n ; n is 1 or 2; A 3 is CR 5 R 6 ; R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are each independently of the others C 1 -C 4 alkyl which may be mono-, di- or tri-substituted by C 1 -C 4 alkoxy, halogen, hydroxy, cyano, hydroxycarbonyl, C 1 -C 4 alkoxycarbonyl, C 1 -C 4 alkylthio, C 1 -C 4 alkylsulfinyl, C 1 -C 4 alkylsulfonyl, C 1 -C 4 alkylcarbonyl, phenyl or by heteroaryl, it being possible for the phenyl and heteroaryl groups in turn to be mono-, di- or tri-substituted by C 1 -C 4 alkoxy, halogen, hydroxy, cyano, hydroxycarbonyl, C 1 -C 4 alkoxycarbonyl, C 1 -C 4 alkylsulfonyl or by C 1 -C 4 haloalkyl, the substituents on the nitrogen in the heterocyclic ring being other than halogen; and/or R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are each independently of the others hydrogen, C 1 -C 4 alkoxy, halogen, hydroxy, cyano, hydroxycarbonyl, C 1 -C 4 alkoxycarbonyl, C 1 -C 4 alkylthio, C 1 -C 4 alkylsulfinyl, C 1 -C 4 alkylsulfonyl, C 1 -C 4 alkylcarbonyl, phenyl or heteroaryl, it being possible for the phenyl and heteroaryl groups in turn to be mono-, di- or tri-substituted by C 1 -C 4 alkoxy, halogen, hydroxy, cyano, hydroxycarbonyl, C 1 -C 4 alkoxycarbonyl, C 1 -C 4 alkylsulfonyl or by C 1 -C 4 haloalkyl, the substituents on the nitrogen in the heterocyclic ring being other than halogen; and/or R 1 and R 2 together form a 3- to 5-membered carbocyclic ring which may be substituted by C 1 -C 4 alkyl and/or interrupted by oxygen, sulfur, S(O), SO 2 , OC(O), NR 7 or by C(O); and/or R 2 and R 4 together or R 2 and R 5 together form a C 1 -C 3 alkylene chain which may be interrupted by oxygen, sulfur, SO, SO 2 , OC(O), NR 8 or by C(O); it being possible for that C 1 -C 3 alkylene chain in turn to be substituted by C 1 -C 4 alkyl; and R 7 and R 8 are each independently of the other C 1 -C 4 alkyl, C 1 -C 4 haloalkyl, C 1 -C 4 alkylsulfonyl, C 1 -C 4 alkylcarbonyl or C 1 -C 4 alkoxycarbonyl; in which process a) a compound of formula II wherein A 1 , A 2 and A 3 are as defined for formula I, is reacted with a bromine or chlorine source to form a compound of formula III wherein A 1 , A 2 and A 3 are as defined for formula I and X is chlorine or bromine; b) that compound is reacted with water to form the compound of formula IV wherein A 1 , A 2 and A 3 are as defined for formula I and X is chlorine or bromine; c) that compound is converted, using a compound of formula V M + -O − —C(O)—Y, (V) wherein Y is as defined hereinbefore and M + is the hydrogen cation or an alkali metal ion, alkaline earth metal ion or ammonium ion, into the compound of formula VI wherein A 1 , A 2 , A 3 and Y are as defined for formula I, and d) then that compound is treated with a cyanide source in the presence of a base.