Catalytic enantioselective synthesis of chiral phthalides by efficient reductive cyclization of 2-acylarylcarboxylates under aqueous transfer hydrogenation conditions.

A new diamine ligand for asymmetric transfer hydrogenation (ATH) was discovered. The reductive cyclization of 2-acylarylcarboxylates was found to proceed highly stereoselectively by the new Ru complex-catalyzed ATH and subsequent in situ lactonization under aqueous conditions. It enables efficient access to a wide variety of 3-substituted phthalides in enantiomerically pure form.