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
Relay catalysis: combined metal catalyzed oxidation and asymmetric iminium catalysis for the synthesis of Bi- and tricyclic chromenes
作者:Magnus Rueping、Jeremy Dufour、Modhu Sudan Maji
DOI:10.1039/c2cc00129b
日期:——
A catalytic asymmetric oxidative iminium-allenaminecascade allows the use of propargyl alcohols as stable substrates and yields valuable chiral bicyclic 4H-chromenes. A subsequent Michael addition-condensation domino reaction provides complex tricyclic 4H-chromenes in a highlyenantioselective fashion.
Iminium-Allenamine Cascade Catalysis: One-Pot Access to Chiral 4H-Chromenes by a Highly Enantioselective Michael-Michael Sequence
作者:Xinshuai Zhang、Shilei Zhang、Wei Wang
DOI:10.1002/anie.200906050
日期:2010.2.15
Taking the Michael‐Michael: A cascadeMichael–Michael reaction of aryl or alkyl alkynals, involving an unprecedented iminium–allenaminesequence, is efficiently catalyzed by a chiral diphenylprolinol TBDMS ether, and affords highly functionalized 4H‐chromenes in high yields. TBDMS=tert‐butyldimethylsilyl.