Catalyst-free chemoselective α-sulfenylation/β-thiolation for α,β-unsaturated carbonyl compounds

A novel, efficient, catalyst-free and product-controllable strategy has been developed for the chemoselective alpha-sulfenylation/beta-thiolation of alpha,beta-unsaturated carbonyl compounds. An aromatic sulfur group could be chemoselectively introduced at alpha- or beta-position of carbonyls with different sulfur reagents under slightly changed reaction conditions. A series of desired products were obtained in moderate to excellent yields. Mechanistic studies revealed that B(2)pin(2) played the key role in activating the transformation towards the beta-thiolation of alpha,beta-unsaturated carbonyl compounds. This transition-metal-catalyst-free method provides a convenient and efficient tool for the highly chemoselective preparation of alpha-thiolation or beta-sulfenylation products of alpha,beta-unsaturated carbonyl compounds.