A Cooperative N-Heterocyclic Carbene/Chiral Phosphate Catalysis System for Allenolate Annulations

摘要

The highly enantioselective NHC-catalyzed [3+2] annulation reaction with α,β-alkynals and α-ketoesters has been developed. A new mode of cooperative catalysis involving the combination of a chiral Bronsted acid and a C1-symmetric biaryl saturated-imidazolium precatalyst was required to generate the desired γ-crotonolactones in high yields and levels of enantioselectivity.