Rhodium(I)-Cataryzed [4+1] Cycloaddition Reactions of α,β-Unsaturated Imines with Terminal Alkynes for the Preparation of Pyrrole Derivatives

摘要

Vinylidene complexes have attracted much attention for being unique reactive intermediate and synthetically useful, and characteristic reactions have been developed using various kinds of transition-metal complexes. One of the main reactions involves the addition of heteroatom nucleo-philes such as alcohols, carboxylates, and carbamates to give anti-Markovnikov addition products. However, the addition of the heteroatom of C=X bonds to the vinylidene carbon atom has rarely been achieved in spite of the high synthetic potential of the zwitterionic intermediates that are produced. Herein, we report a rhodium(I)-catalyzed [4+1] cycloaddition reaction between α,β-unsaturated imines and terminal alkynes for the preparation of synthetically useful, substituted pyrrole derivatives through the addition of the imine nitrogen atom to rhodium vinylidene intermediates.