oxidation and dehydroxylation, respectively. Using the modularly designed organocatalysts (MDOs) self-assembled from cinchonaalkaloidderivatives and amino acids in the reaction media, the title products were obtained in good to high yields (up to 97%) and excellent diastereoselectivities (up to 99 : 1 dr) and enantioselectivities (up to 99% ee).
Organocatalytic Asymmetric Tandem Michael Addition−Hemiacetalization: A Route to Chiral Dihydrocoumarins, Chromanes, and 4<i>H</i>-Chromenes
作者:Dengfu Lu、Yajun Li、Yuefa Gong
DOI:10.1021/jo101446d
日期:2010.10.15
Asymmetric tandem Michael addition−hemiacetalization between aliphatic aldehydes and (E)-2-(2-nitrovinyl)phenols was investigated for constructing benzopyran backbones. Interestingly, the diastereo- and enantioselectivities changed markedly when the reaction was mediated by different types of secondary amine catalysts. The diphenylprolinol silyl ether 7 promoted the reaction with excellent enantioselectivities