Organocatalytic Asymmetric Michael Addition of 3-Pyrrolyloxindoles to β-Phthalimidonitroethene for the Synthesis of 3,3′-Disubstituted Oxindoles Bearing Contiguous 3,α,β-Triamino Functionality

An organocatalytic asymmetric Michael addition reaction of 3-pyrrolyloxindoles to β-phthalimidonitroethene has been developed with a bifunctional thiourea-tertiary amine as the catalyst. A range of 3,3'-disubstituted oxindoles bearing contiguous 3,α,β-triamino functionality could be obtained in high yields with good diastereoselectivities and high enantioselectivities (up to 99% yield, 99:1 dr, and 98% ee). The higher reactivity of β-phthalimidonitroethene compared to the reactivity of ordinary nitroalkenes in the reaction with 3-pyrrolyloxindoles was demonstrated by contrast experiments.