were used in situ to promote the asymmetric selenocyclization of γ-alkenyl oximes and δ-phenyl-γ-alkenyl oximes. The course of these reactions and hence the structures of the cyclization products were dictated by the (E)- or (Z)-geometry of the starting oximes. The two types of cyclization products were either the cyclicnitrones or the 1,2-oxazines; in both cases the reactions proceeded with excellent
Kinetic resolution of 2-methoxycarbonylalk-3-enols through a stereoselective cyclofunctionalization promoted by an enantiomerically pure electrophilic selenium reagent
作者:Cristina Tomassini、Francesca Di Sarra、Bonifacio Monti、Luca Sancineto、Luana Bagnoli、Francesca Marini、Claudio Santi
DOI:10.3998/ark.5550190.p009.826
日期:——
In this manuscript the kinetic resolution of 2-methoxycarbonylalk-3-enols is reported through a stereoselective selenocyclization promoted by an electrophilic sulfur-containing selenium reagent. Reacting one equivalent of the selenenenylating agent with two equivalents of racemic starting material afforded a mixture of a stereoselectively enriched tetrahydrofuran and the corresponding enantiomerically enriched alkenols.[GRAPHICS].
A sulfur-containing diselenide as an efficient chiral reagent in asymmetric selenocyclization reactions
Treatment of the di-2-[(IS)-1-(methylthio)ethyl]phenyl diselenide with bromine and silver triflate afforded the corresponding selenyl triflate which was used in situ as a strongly electrophilic selenium reagent to effect the asymmetric synthesis of oxygen- or nitrogen-containing heterocycles. Cyclic ethers, lactones, lactams or N-protected pyrrolidines have been prepared in good yield with complete regioselectivity and high diastereoselectivity. (C) 2001 Elsevier Science Ltd. All rights reserved.