Distal Allylic/Benzylic C−H Functionalization of Silyl Ethers Using Donor/Acceptor Rhodium(II) Carbenes
Janakiram Vaitla, Yannick T. Boni, Huw M. L. Davies
Abstract
Abstract Regio‐ and stereoselective distal allylic/benzylic C−H functionalization of allyl and benzyl silyl ethers was achieved using rhodium(II) carbenes derived from N‐sulfonyltriazoles and aryldiazoacetates as carbene precursors. The bulky rhodium carbenes led to highly site‐selective functionalization of less activated allylic and benzylic C−H bonds even in the presence of electronically preferred C−H bonds located α to oxygen. The dirhodium catalyst Rh 2 (S‐NTTL) 4 is the most effective chiral catalyst for triazole‐derived carbene transformations, whereas Rh 2 (S‐TPPTTL) 4 works best for carbenes derived from aryldiazoacetates. The reactions afford a variety of δ‐functionalized allyl silyl ethers with high diastereo‐ and enantioselectivity. The utility of the present method was demonstrated by its application to the synthesis of a 3,4‐disubstituted l ‐proline scaffold.