Palladium-Catalyzed Stereospecific C-Glycosylation of Glycals with Vinylogous Acceptors

A palladium-catalyzed vinylogous C-glycosylation of α,β-unsaturated lactones (including coumarins) is achieved in high yields with exclusive regio- and stereoselectivity. This efficient protocol is carried out under mild conditions and has an expanded substrate scope (51 examples) as well as high functional-group tolerance. A gram-scale preparation of 2,3-unsaturated C-glycosides illustrates the practicality of this stereoselective vinylogous glycosylation approach. The structural feature of C-glycoside products enables subsequent transformations and provides a wide range of multifunctional and diverse compounds.