Iridium-catalyzed asymmetric hydrogenation of racemic α-substituted lactones to chiral diols.

We report a protocol for the highly efficient iridium-catalyzed asymmetric hydrogenation of racemic α-substituted lactones via dynamic kinetic resolution. Using Ir-SpiroPAP ( R )- 1d as a catalyst, a wide range of chiral diols were prepared in a high yield (80-95%) with a high enantioselectivity (up to 95% ee) under mild reaction conditions. This protocol was used for enantioselective syntheses of (-)-preclamol and a chiral 2,5-disubstituted tetrahydropyran.