Patent ID: 7521565

Claim:
A process for preparing a compound of formula 1, which comprises: allowing a compound of formula 2 to react with a compound of formula 3A or 3B and a compound of formula 4 in the presence of an acid, an alkylsilylhalide compound or an acylhalide compound, in a solvent: wherein R 1 , R 2 , R 3 and R 4 are each independently C 1-6 alkyl or phenyl; or R 1 and R 3 , and R 2 and R 4 are fused together with the nitrogen atoms to which they are attached to form a 6-membered heterocycloalkyl group optionally containing O; and R 1′ , R 2′ and R 5 are each independently C 1-6 alkyl or aryl.