Enantioselective epoxidations of alkenes (12 examples) were achieved using a Shi-type carbohydrate-derived hydrate and Oxone. The chiral platform provided by the catalyst tolerates a wide range of substituents providing high yields and enantioselectivities (80-95.5% ee). However, styrene derivatives were only converted with poor selectivities (11-26% ee).
Accessible sugars as asymmetric olefin epoxidation organocatalysts: glucosaminide ketones in the synthesis of terminal epoxides
作者:Omar Boutureira、Joanna F. McGouran、Robert L. Stafford、Daniel P. G. Emmerson、Benjamin G. Davis
DOI:10.1039/b911675c
日期:——
A systematically varied series of conformationally restricted ketones, readily prepared from N-acetyl-D-glucosamine, were tested against representative olefins as asymmetric epoxidation catalysts showing useful selectivities against terminal olefins and, in particular, typically difficult 2,2-disubstituted terminal olefins.
Catalytic asymmetric epoxidation of alkenes with arabinose-derived uloses
作者:Tony K.M Shing、Yiu C Leung、Kwan W Yeung
DOI:10.1016/s0040-4020(03)00145-5
日期:2003.3
Four l-erythro-2-uloses were readily prepared from l-arabinose via a reaction sequenceinvolving Fischer glycosidation, acetalization and oxidation. Bulky steric sensors at the anomeric center could enhance the stereoselectivity of the dioxirane epoxidation and one of the uloses performed with good enantioselectivity towards trans-stilbene (up to 90% ee). However, the catalysts decomposed during the
Arabinose-Derived Ketones as Catalysts for Asymmetric Epoxidation of Alkenes
作者:Tony K. M. Shing、Gulice Y. C. Leung、To Luk
DOI:10.1021/jo050928f
日期:2005.9.1
Readily available arabinose-derived ketones, containing a tunable butane-2,3-diacetal as the steric blocker, displayed increasing enantioselectivity (up to 90% ee) with the size of the acetal alkyl group in catalytic asymmetricepoxidation of trans-disubstituted and trisubstituted alkenes. The stereochemical communication between our ketonecatalysts and the alkene substrates is mainly due to steric
Asymmetric Epoxidation Using Iminium Salt Organocatalysts Featuring Dynamically Controlled Atropoisomerism
作者:Philip C. Bulman Page、Christopher J. Bartlett、Yohan Chan、David Day、Phillip Parker、Benjamin R. Buckley、Geracimos A. Rassias、Alexandra M. Z. Slawin、Steven M. Allin、Jérôme Lacour、André Pinto
DOI:10.1021/jo300915u
日期:2012.7.20
Introduction of a pseudoaxial substituent at a stereogenic center adjacent to the nitrogen atom in binaphthyl- and biphenyl-derived azepinium saltorganocatalysts affords improved enantioselectivities and yields in the epoxidation of unfunctionalized alkenes. In the biphenyl-derived catalysts, the atropoisomerism at the biphenyl axis is controlled by the interaction of this substituent with the chiral