Catalytic Asymmetric α-Alkylsulfenylation with a Disulfide Reagent.

The use of alkylthio electrophiles in synthesis has remained elusive because of the lack of a suitable reagent that is practical and of excellent enantioselectivity and appropriate reactivity. In this work we introduce a novel alkylthio reagent based on the 2-mercapto-5-methyl-1,3,4-thiadiazole (MMTD) fragment for direct alkylsulfenylation of ketones and aldehydes. It can be readily prepared by the oxidative coupling between thiadiazole and other alkylthio reagents and be combined with chiral primary aminocatalysis. This protocol provides facile access to diverse α-alkylthio quaternary carbon centers with good stereoselectivities.