A general copper-catalysed enantioconvergent C(sp3)–S cross-coupling via biomimetic radical homolytic substitution

Although α-chiral C(sp3)–S bonds are of enormous importance in organic synthesis and related areas, the transition-metal-catalysed enantioselective C(sp3)–S bond construction still represents an underdeveloped domain probably due to the difficult heterolytic metal–sulfur bond cleavage and notorious catalyst-poisoning capability of sulfur nucleophiles. Here we demonstrate the use of chiral tridentate anionic ligands in combination with Cu(I) catalysts to enable a biomimetic enantioconvergent radical C(sp3)–S cross-coupling reaction of both racemic secondary and tertiary alkyl halides with highly transformable sulfur nucleophiles. This protocol not only exhibits a broad substrate scope with high enantioselectivity but also provides universal access to a range of useful α-chiral alkyl organosulfur compounds with different sulfur oxidation states, thus providing a complementary approach to known asymmetric C(sp3)–S bond formation methods. Mechanistic results support a biomimetic radical homolytic substitution pathway for the critical C(sp3)–S bond formation step.