Cyclophane-Type Imidazolium Salts with Planar Chirality as a New Class of N-Heterocyclic Carbene Precursors
作者:Yuki Matsuoka、Yasuhiro Ishida、Daisuke Sasaki、Kazuhiko Saigo
DOI:10.1002/chem.200800942
日期:2008.10.20
Cyclophane-type imidazolium salts with planar chirality were synthesized from enantiopure 2-amino alcohols, of which the N(1) and N(3) positions were connected with a bridge. The structural profiles of the imidazolium salts and their derivative N-heterocyclic carbenes (NHCs) were investigated by means of several analyses. The chiral NHCs derived from these imidazolium salts were found to catalyze the
由对映体纯的2-氨基醇合成了具有平面手性的环烷型咪唑鎓盐,其中N(1)和N(3)位置通过桥连接。咪唑鎓盐及其衍生物N-杂环卡宾(NHCs)的结构轮廓通过数种分析方法进行了研究。已发现衍生自这些咪唑鎓盐的手性NHC借助烯类的“共轭”蛋白酚催化酮类的α,β-不饱和醛与酮的不对称交叉环化,从而得到具有良好或优异性能的目标γ-内酯对映选择性(高达94%ee)。基于NHC及其中间体的预期结构,以及产品的绝对构型,提出了一种可行的立体控制机制。