Catalytic asymmetric synthesis of 2,2-disubstituted terminal epoxides via dimethyloxosulfonium methylide addition to ketones

Catalytic asymmetric Corey-Chaykovsky epoxidation of ketones with dimethyloxosulfonium methylide 2 using an LLB 1a + Ar3P = O complex proceeded smoothly at room temperature, and 2,2-disubstituted termimal epoxides were obtained in high enantioselectivity (91-97%) and yield (> 88-99%) from a broad range of methyl ketones with 1-5 mol % catalyst loading. The use of achiral addictive Ar3P = O 5i was important to achieve high enantioselectivity.