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

作者：Zheng Bo; Hou Wenduan; Peng Yungui^*

来源：ChemCatChem, 2014, 6(9): 2527-2530.

DOI：10.1002/cctc.201402236

• asymmetric catalysis
• cascade reactions
• hydrogenation
• squaramides

A series of chiral squaramides were employed in the oxa-Michael-aza-Henry cascade reaction of 2-hydroxyaryl-substituted -amido sulfones and nitroolefins. In the presence of 10mol% of a squaramide catalyst and K2CO3 (aq) in CHCl3 at 0 degrees 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.

• 出版日期2014-9