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.