Catalytic asymmetric synthesis of 3,2′-pyrrolinyl spirooxindoles <i>via</i> conjugate addition/Schmidt-type rearrangement of vinyl azides and (<i>E</i>)-alkenyloxindoles

Abstract

A catalytic asymmetric conjugate addition/Schmidt-type rearrangement of vinyl azides and (<i>E</i>)-alkenyloxindoles was realized. It afforded a variety of optically active 3,2'-pyrrolinyl spirooxindoles with high yields (up to 98%), and excellent diastereo- and enantioselectivities (up to 98% ee, >19 : 1 dr), even at the gram-scale in the presence of a chiral <i>N</i>,<i>N</i>'-dioxide-nickel(ii) complex. In addition, a possible catalytic cycle and transition state model were proposed to rationalize the stereoselectivity.