Fulvenes as Effective Dipolarophiles in Copper(I)-Catalyzed [6+3] Cycloaddition of Azomethine Ylides: Asymmetric Construction of Piperidine Derivatives

摘要

Catalytic asymmetric [3+2] cycloaddition of azomethine ylides is one of the best methods for constructing enantio-enriched heterocyclic pyrrolidines, and extensive studies have been conducted on the use of various electron-deficient alkenes as the 2π synthons over the past decade. However, although there are elegant and creative azomethine-ylide-involved cycloaddition reactions toward the construction of five-membered pyrrolidine architectures, the direct catalytic asymmetric approach to enantioenriched six-membered heterocyclic piperidines, which are prevalent scaffolds that serve as the core structures of natural alkaloids and bioactive molecules, has met with little success, and we believe this represents a considerable challenge.