Asymmetric oxa-Michael-aza-Henry Cascade Reaction of 2-Hydroxyaryl-Substituted α-Amido Sulfones and Nitroolefins Mediated by Chiral Squaramides

Authors

  • Dr. Bo Zheng,

    1. School of Chemistry and Chemical Engineering, Southwest University, 2 N. Tiansheng Road, Chongqing, 400715, (P. R. China), Fax: (+86) 23-68253157
    Search for more papers by this author
  • Dr. Wenduan Hou,

    1. School of Chemistry and Chemical Engineering, Southwest University, 2 N. Tiansheng Road, Chongqing, 400715, (P. R. China), Fax: (+86) 23-68253157
    Search for more papers by this author
  • Prof. Yungui Peng

    Corresponding author
    1. School of Chemistry and Chemical Engineering, Southwest University, 2 N. Tiansheng Road, Chongqing, 400715, (P. R. China), Fax: (+86) 23-68253157
    • School of Chemistry and Chemical Engineering, Southwest University, 2 N. Tiansheng Road, Chongqing, 400715, (P. R. China), Fax: (+86) 23-68253157

    Search for more papers by this author

Abstract

A series of chiral squaramides were employed in the oxa-Michael-aza-Henry cascade reaction of 2-hydroxyaryl-substituted α-amido sulfones and nitroolefins. In the presence of 10 mol % of a squaramide catalyst and K2CO3 (aq) in CHCl3 at 0 °C, this reaction proceeded smoothly to afford chiral multisubstituted 4-amino-3-nitrobenzopyrans, bearing a readily removable N-Boc protecting group (Boc=tert-butoxycarbonyl), in excellent yields (up to 98 %) and enantioselectivity [up to 98:2 enantiomeric ratio (er) and 93:7 diastereomeric ratio (dr)]. The 4-amino-3-nitrobenzopyrans were converted into chiral 3,4-diamino chromanes, which were further exploited as chiral ligands in the asymmetric transfer hydrogenation of acetophenone, providing 1-phenylethanol in up to 84 % yield and 93.5:6.5 er.

Ancillary