2-Carboxythioester-1,3-dithiane: a functionalized masked carbonyl nucleophile for the organocatalytic enantioselective Michael addition to enones

An S-(2,2,2-trifluoroethyl) 1,3-dithiane-2-carbothioate has been successfully employed as acyl anion synthon in the organocatalytic enantioselective addition to enones promoted by quinine- and quinidine-derived tertiary/primary diamines. By proper selection of a co-catalyst and by optimization of the reaction parameters, convenient experimental conditions were found that allowed to obtain the highly functionalized products in up to 90% yield and 98% ee in short reaction times. These compounds, featuring selectively removable functionalities, proved to be versatile synthetic intermediates, which could be transformed into different derivatives without any erosion of the stereochemical integrity of the molecules.