α-C-H Difluoroalkylation of Alkyl Sulfoxides via Intermolecular Pummerer Reaction

Pummerer reaction is a well-known protocol for α-functionalization of alkyl sulfoxides. However, in contrast to the progress in developing intramolecular variants, the development of intermolecular Pummerer-type C–C coupling reactions has lagged with limited success, which relies heavily on the use of bases and/or Lewis acids. Herein, we demonstrate that difluoroenol silyl ether is an effective C-nucleophile to perform intermolecular Pummerer reaction without any additives, leading to highly selective α-C–H difluoroalkylation of a wide variety of alkyl sulfoxides including drug analogues and natural product derivatives. Mechanistic studies reveal that the success of the reaction originates from the electron withdrawing effect of fluorine in difluoroenol silyl ether which gives it the ability to distinguish different S(IV) species.