Patent ID: 7977509

Claim:
A process for the preparation of a compound of formula I: wherein: R 1 is selected from the group consisting of: (1) hydrogen, (2) C 1 -C 8 alkyl, which is unsubstituted or substituted by one or more substituents selected from the group consisting of C 1 -C 8 alkoxy and C 3 -C 8 cycloalkyl, and (3) C 2 -C 8 alkenyl which is unsubstituted or substituted by one or more substituents selected from the group consisting of C 1 -C 8 alkoxy and C 3 -C 8 cycloalkyl; and R 2 and R 3 are combined with the carbon atom to which they are attached to form C 3 -C 7 cycloalkyl or C 5 -C 8 cycloalkenyl; comprising reacting a compound of formula II: wherein R 1 , R 2 and R 3 have the above meanings; with thionylchloride in the presence of tributylamine and an aliphatic hydrocarbon solvent.