Asymmetric Intramolecular Oxa-Michael Reactions to Tetrahydrofurans/2<i>H</i>-Pyrans Catalyzed by Primary–Secondary Diamines
作者:Yingpeng Lu、Gang Zou、Gang Zhao
DOI:10.1021/cs4002332
日期:2013.6.7
The asymmetricintramolecularoxa-Michaelreactions of α,β-unsaturated ketones have been achieved by using readily accessible primary–secondary diamines as the organocatalysts, giving the synthetically useful tetrahydrofurans/2H-pyrans in good yields and with high enantioselectivities (up to 90% ee).
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.