Chiral Bronsted acid-catalyzed enantioselective ionic [2+4] cycloadditions
Chiral Bronsted acid-catalyzed enantioselective ionic [2+4] cycloadditions
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DOI：
10.1016/j.tet.2013.03.086
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发表时间：
2013-07-08
期刊：
影响因子：
2.1
通讯作者：
Nagorny, Pavel
中科院分区：
文献类型：
--
作者：
Borovika, Alina;Nagorny, Pavel
报道了不饱和缩醛的第一个不对称手性N-三氟甲酰基磷酰胺催化的离子[2+4]环加成反应。该反应通过乙烯基氧碳正离子/手性阴离子对的中间体进行，并且手性N-三氟甲酰基磷酰胺阴离子控制环加成步骤的立体选择性。中等的对映体选择性（高达80：20 es.）当α，β-不饱和二氧戊环用作亲二烯体时，这些反应表现出强烈的依赖于配位性质和溶剂极性，oxocarbenium离子的行为特征。(C)2013爱思唯尔有限公司保留所有权利。
The first asymmetric chiral N-triflylphosphoramide-catalyzed ionic [2+4] cycloaddition reaction of unsaturated acetals is described. This reaction proceeds through the intermediacy of a vinyl oxocarbenium/chiral anion pair, and the chiral N-triflylphosphoramide anion controls the stereoselectivity of the cycloaddition step. Moderate enantioselectivities (up to 80:20 es.) have been obtained when alpha,beta-unsaturated dioxolanes were employed as the dienophiles. These reactions demonstrate strong dependence on the counterion coordinating properties and solvent polarity, a behavior characteristic of oxocarbenium ions. (C) 2013 Elsevier Ltd. All rights reserved.