Asymmetric [3 + 2] Cycloaddition of Methyleneindolinones with N,N鈥?Cyclic Azomethine Imines Catalyzed by a N,N鈥?Dioxide鈥揗g(OTf)2 Complex
文摘
A highly efficient chiral N,N鈥?dioxide鈥揗g(OTf)2 catalyst system has been developed for the asymmetric 1,3-dipolar cycloaddition between methyleneindolinones and N,N鈥?cyclic azomethine imines. The desired pyrazolidine products with contiguous quaternary鈥搕ertiary stereocenters were obtained in up to 99% yields with up to 99% ee and >19:1 dr under mild reaction conditions.