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Enantioselective Vinylogous Mannich Reaction of Acyclic Vinylketene Silyl Acetals with Ketimines Using Chiral Bis(imidazoline)–Cu(II) Catalysts

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journal contribution
posted on 12.02.2020, 20:14 authored by Shuichi Nakamura, Koichi Matsuzaka, Tsubasa Hatanaka, Yasuhiro Funahashi
The enantioselective vinylogous Mannich reaction of ketimines derived from isatins with acyclic vinylketene silyl acetals has been developed using a chiral bis­(imidazoline)–Cu­(II) catalyst. A series of chiral 3-aminooxindole derivatives bearing tetra-substituted stereogenic centers with an α,β-unsaturated ester moiety were obtained in excellent yields (up to 99%) with high enantioselectivities (up to 98% ee). Enantioselective bisvinylogous Mannich reaction to ketimines derived from isatins also afforded product with high enantioselectivity. Based on the experimental investigations, a possible transition state has been proposed to explain the origin of the asymmetric induction.