Asymmetric Mannich reaction of N-Boc aminosulfones with 3-methylbenzofuran-2 (3H) - Ones catalyzed by a chiral phase-transfer catalyst

An enantioselective Mannich reaction of N-Boc aminosulfones with 3-methylbenzofuran-2 (3H)-ones catalyzed by a quinine-derived bifunctional phase transfer catalyst was developed, by which a series of chiral benzofuranones bearing adjacent quaternary and tertiary carbon centers were obtained in high yields (up to 96%) with good diastereoselectivities (up to >99:1) and enantioselectivities (up to 98%).