Rhodium(I)/Zn(OTf)2 -Catalyzed Asymmetric Ring Opening/Cyclopropanation of Oxabenzonorbornadienes with Phosphorus Ylides.

Abstract

The strong binding ability of P-ylides with transition metals limits the utilization of stabilized P-ylide as nucleophiles in asymmetric organometallic catalysis. Herein we describe the first rhodium-catalyzed asymmetric ring-opening reaction of P-ylides utilizing oxabicyclic alkenes as the electrophilic partner. Various P-ylides including ester-, ketone- and amide-style P-ylides are all applicable. This asymmetric reaction occurs through the cleavage of two bridgehead C-O bonds and the formation of two C-C bonds, and oxabenzonorbornadienes are used as 1,4-biselectrophiles, thus providing access to benzonorcaradienes in good yields with high enantioselectivity and perfect diastereoselectivity. The present protocol also constitutes the first highly enantioselective direct catalytic asymmetric cyclopropanation of stabilized P-ylide nucleophiles.