Patent ID: 8106224

Claim:
A method for the preparation of a compound of formula (I): wherein Z represents a C 1-6 -alkyl, C 2-6 -alkenyl, C 3-8 -cycloalkyl, aryl, heteroaryl, aryl C 1-6 -alkyl, or heteroaryl-C 1-6 -alkyl group, optionally substituted by one to three groups independently chosen from the group consisting of halogen, C 1-6 -alkyl and C 1-6 -alkylthio, comprising the following steps: (a) reacting a compound of formula (II): with a sulfonic derivative of formula (III) wherein R is chosen from the group consisting of C 1-3 -alkyl, C 1-3 -alkyl substituted with 1 to 3 halogen atoms, phenyl, C 1-3 -alkyl-phenyl and C 1-3 -alkyl-phenyl; wherein the alkyl is substituted with 1 to 3 halogen atoms and G is a halogen atom or —O—SO 2 —R; wherein R is as hereinabove defined, to yield a compound of formula (IV) wherein R has the meaning defined for formula (III); (b) treating compound (IV) with a thiocarboxylic acid of formula (V) or a salt thereof: wherein Z is as defined for formula (I), to yield compound (VI); wherein Z is as defined for formula (I) and R is as defined for formula (III); and (c) treating compound (VI) with tetrabutylammonium nitrate to yield a compound of formula (I).