Catalytic enantioselective cascade Michael/ cyclization reaction of 3-isothiocyanato oxindoles with exocyclic α,β-unsaturated ketones en route to 3,2'-pyrrolidinyl bispirooxindoles

摘要

Cascade Michael/cyclization reactions between 3-isothiocyanato oxindoles and exocyclic α,β-unsaturated ketones are shown to proceed efficiently in the presence of a quinine-derived tertiary amino-squaramide catalyst and furnish 3,2'-pyrrolidinyl bispiro-oxindoles containing two spiro-quaternary and three contiguous stereocenters as a single diastereomer with excellent enantio-selectivities (up to 99:1 er).