Planar chiral imidazolium salts based on [2.2]paracyclophane in the asymmetric rhodium-catalyzed 1,2-addition of arylboronic acids to aldehydes
摘要:
A series of planar chiral imidazolium salts derived from [2.2]paracyclophane have been synthesized and characterized. By using these imidazolium salts as carbene precursors, the Rh-catalyzed 1,2-addition of arylboronic acids to aldehydes proceeded readily with low catalyst loadings (0.03-0.3 mol %) and gave a variety of chiral diarylmethanols in excellent yields and moderate enantioselectivities. (C) 2010 Elsevier Ltd. All rights reserved.
通过一种新的合成途径,获得了由[2.2]对环网衍生而来的,具有受限挠性的独特的平面手性对称N-杂环卡宾前体家族。4-氨基-13-溴[2.2]对环环烷的拆分以相对较高的效率实现。从(4 S p,13 R p)-4-氨基-13-溴[2.2]对环环磷酰胺开始,以四个步骤的顺序制备了平面手性假宝石-二取代的[2.2]对环环磷酰基二氢咪唑鎓,并具有良好的收率。用包括单晶X射线衍射技术在内的一系列方法对所得的二氢咪唑鎓盐进行了充分表征。