Organocatalytic Access to Enantioenriched Spirooxindole-Based 4-Methyleneazetidines
Giulia Rainoldi,
Matteo Faltracco,
Claudia Spatti,
Alessandra Silvani,
Giordano Lesma
Affiliations
Giulia Rainoldi
Department of Chemistry, University of Milan, via Golgi 19, 20133 Milan, Italy
Matteo Faltracco
Department of Chemistry & Pharmaceutical Sciences, Amsterdam Institute of Molecules Medicines & Systems (AIMMS), Vrije Universiteit Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam, The Netherlands
Claudia Spatti
Department of Chemistry, University of Milan, via Golgi 19, 20133 Milan, Italy
Alessandra Silvani
Department of Chemistry, University of Milan, via Golgi 19, 20133 Milan, Italy
Giordano Lesma
Department of Chemistry, University of Milan, via Golgi 19, 20133 Milan, Italy
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.
