The novel benzosultam-fused 4-imidazolidinone scaffold was constructed by a concise [3 + 2] annulation reaction of αhalogenated hydroxamates and N-sulfonyl ketimine for the first time. The transformation proceeded smoothly under mild and transition-metal-free conditions in moderate to excellent yields (up to 95 %). Moreover the annulation products are potentially useful and promising for medicinal research.

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.