A Highly Enantioselective Approach to Hydrocarbazole Derivatives Catalyzed by Diphenylmethylidene Bis(oxazoline)-Ni(II) Complexes

摘要

The first Ni(II)-catalyzed asymmetric [4+2] cycloaddition of silyloxyvinylindoles with 2-enoyl pyridines was successfully accomplished by using a diphenylmethylidene-tethered bis(oxazoline). A series of optically active hydrocarbazole derivatives with three contiguous stereocenters were achieved in good yield with both high diastereo-(>20 : 1) and enantioeselectivities (up to 97 % ee) under mild conditions. Moreover, various 2-enoyl azaarenes were compatible with the reaction. A proposed mechanism was deducted.