Enantioselective organocatalytic domino Michael–acetalization–Henry reactions of 2-hydroxynitrostyrene and aldehyde for the synthesis of tetrahydro-6H-benzo[c]chromenones
作者:Bor-Cherng Hong、Prakash Kotame、Ju-Hsiou Liao
DOI:10.1039/c0ob00834f
日期:——
Asymmetric domino Michael–acetalization reactions of 2-hydroxynitrostyrene and aldehydes “on water” followed by oxidation providing the cis-3,4-disubstituted dihydrocoumarins with excellent enantioselectivities (up to >99% ee). The variant with glutaraldehyde underwent a highly stereoselective domino Michael–acetalization–Henry reaction to afford the tetrahydro-6H-benzo[c]chromen-6-ones after the subsequent
不对称多米诺骨牌迈克尔缩醛化反应 2-羟基硝基苯乙烯 和醛“上 水然后进行氧化,使顺式-3,4-二取代的二氢香豆素具有出色的对映选择性(高达> 99%ee)。具有的变体戊二醛进行高度立体选择性的多米诺骨牌Michael-缩醛化-Henry反应,在随后的氧化反应后得到四氢-6 H-苯并[ c ] chromen-6-one。
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
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).
Heterogeneous enantioselective synthesis of chromans via the oxa-Michael–Michael cascade reaction synergically catalyzed by grafted chiral bases and inherent hydroxyls on mesoporous silica surface
作者:Shanshan Wang、Jing He、Zhe An
DOI:10.1039/c7cc03556j
日期:——
A heterogeneous enantioselective oxa-Michael–Michael reaction for the synthesis of chromans has been developed on a heterogeneous acid–base synergic catalyst with inherent silica as acidic sites and immobilized chiral amines as basic sites. Final products were afforded in selectivity of up to 98% and ee of 97% from 2-nitrovinyl phenol and 3-methyl-2-butenal. The heterogeneous synergistic catalytic