Patent ID: 7351836

Claim:
A process for the preparation of a compound of formula I, wherein: R 1 represents aryl or heteroaryl optionally substituted with one or more groups independently selected from halogen, C 1-8 alkyl, C 1-8 haloalkyl, R 2 OC 0-8 alkyl, R 2 SC 0-8 alkyl, cyano, nitro, —NR 2 R 4 , —NR 2 SO 2 R 3 , —SOR 3 , —SO 2 R 3 , —SO 2 NR 2 R 4 or —CONR 2 R 4 ; R 2 represents hydrogen, C 1-8 alkyl or arylC 0-8 alkyl (wherein the aryl group can be optionally substituted with one or more groups selected from C 1-8 alkyl, halogen, C 1-8 haloalkyl, cyano, nitro, R 5 OC 0-8 alkyl, R 5 SC 0-8 alkyl, —NR 5 R 6 , —NR 5 COR 3 , —COR 5 or —COOR 5 ); R 3 represents C 1-8 alkyl or C 1-8 haloalkyl; R 4 represents hydrogen, C 1-8 alkyl, arylC 1-8 alkyl (wherein the aryl group can be optionally substituted with one or more groups selected from C 1-8 alkyl, halogen, C 1-8 haloalkyl, cyano, nitro, R 5 OC 0-8 alkyl, R 5 SC 0-8 alkyl, —NR 5 R 6 , —NR 5 COR 3 , —COR 5 , or —COOR 5 ), —COR 6 or —COOR 6 ; R 5 represents hydrogen, C 1-8 alkyl or benzyl; R 6 represents C 1-8 alkyl or C 1-8 haloalkyl; aryl represents phenyl or naphthyl; and heteroaryl represents pyridine, pyrazine, pyrimidine or pyridazine, which can be optionally fused to a benzene ring; which comprises treating a compound of formula II wherein R 1 has the meaning defined above in relation to the formula I and Bu t represents tert-butyl, with an acid.