Asymmetric chroman synthesis via an intramolecular oxy-Michael addition by bifunctional organocatalysts
作者:Ryota Miyaji、Keisuke Asano、Seijiro Matsubara
DOI:10.1039/c3ob41938j
日期:——
organocatalysts facilitate the catalytic asymmetric synthesis of chroman derivatives via an intramolecular oxy-Michael addition reaction. Phenol derivatives bearing an easily available (E)-α,β-unsaturated ketone or a thioester moiety are useful substrates for the title transformation. This method represents a facile synthesis of various optically active 2-substituted chromans in high yield.
<i>N</i>-Heterocyclic Carbene-Catalyzed Conjugate Additions of Alcohols
作者:Eric M. Phillips、Matthias Riedrich、Karl A. Scheidt
DOI:10.1021/ja1061196
日期:2010.9.29
An efficient intermolecular conjugateaddition of alcohols to activated alkenes catalyzed by N-heterocyclic carbenes has been developed. With 5 mol % of the free carbene derived from IMes·HCl, unsaturated ketones and esters are competent substrates, and a variety of primary and secondary alcohols can be employed as the nucleophile. No oligomerization is observed under these mild conditions for effective
Organocatalytic Enantioselective Cycloetherifications Using a Cooperative Cation-Binding Catalyst
作者:Amol P. Jadhav、Jeong-A Oh、In-Soo Hwang、Hailong Yan、Choong Eui Song
DOI:10.1021/acs.orglett.8b02240
日期:2018.9.7
A highly enantioselective cycloetherification strategy for the straightforward synthesis of enantioenriched tetrahydrofurans, tetrahydropyrans, and oxepanes using Song’s cation-binding oligoEG catalyst and KF as the base is demonstrated. A wide range of ε-, ζ-, and η-hydroxy-α,β-unsaturated ketones were cyclized to the corresponding five-, six-, and seven-membered chiral oxacycles with high enantiopurity
Asymmetric Catalytic Cycloetherification Mediated by Bifunctional Organocatalysts
作者:Keisuke Asano、Seijiro Matsubara
DOI:10.1021/ja207322d
日期:2011.10.26
Oxacyclic structures such as tetrahydrofuran (THF) rings are commonly found in many bioactive compounds, and this has led to several efforts toward their stereoselective syntheses. However, the process of catalytic asymmetric cycloetherification for their straightforward synthesis has remained a challenge. In this study, we demonstrate a novel asymmetric synthesis method for THF via the catalytic cycloetherification of epsilon-hydroxy-alpha,beta-unsaturated ketones mediated by cinchona-alkaloid-thiourea-based bifunctional organocatalysts. This catalytic process represents a highly practical cycloetherification method that provides excellent enantioselectivities, even with low catalyst loadings at ambient temperature.