Organocatalytic Access to Enantioenriched Spirooxindole-Based 4-Methyleneazetidines
Giulia Rainoldi1, Matteo Faltracco2, Claudia Spatti3
1Department of Chemistry, University of Milan, via Golgi 19, 20133 Milan, Italy. giulia.rainoldi@unimi.it.
Abstract:
This work describes the synthesis of enantioenriched spiro compounds, incorporating the azetidine and the oxindole motifs. The preparation relies on a formal [2 + 2] annulation reaction of isatin-derived N-tert-butylsulfonyl ketimines with allenoates. The asymmetric induction is secured by an organocatalytic strategy, exploiting a bifunctional cinchona-type β-isocupridine-based catalyst. Some post-transformation products, including unexpected spiropyrroline and 3,3-disubstituted oxindole derivatives, are also presented.
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