Catalytic enantioselective synthesis of chiral phthalides by SmI2-mediated reductive cyclization of 2-acylarylcarboxylates.

A significant new and efficient catalytic asymmetric approach for the highly enantioselective synthesis of chiral phthalides by SmI2-induced reductive cyclization of 2-acylarylcarbonylates was developed. The combination of (4S,5R)-4,5-diphenyloxazolidin-2-one and 2,2,6,6-tetramethylpiperidine was found to be a very effective catalyst system in the reaction. This method provides a ready access to a broad range of enantiomerically enriched phthalides (up to 99% ee).