Allenes in Asymmetric Catalysis: Asymmetric Ring Opening of <i>meso</i>-Epoxides Catalyzed by Allene-Containing Phosphine Oxides
作者:Xiaotao Pu、Xiangbing Qi、Joseph M. Ready
DOI:10.1021/ja9041127
日期:2009.8.5
Unsymmetrically substituted allenes (1,2-dienes) are inherently chiral and can be prepared in optically pure form. Nonetheless, to date the allene framework has not been incorporated into ligands for asymmetric catalysis. Since allenes project functionality differently than either tetrahedral carbon or chiral biaryls, they may create complementary chiral environments. This study demonstrates that optically
不对称取代的丙二烯(1,2-二烯)本质上是手性的,可以以光学纯的形式制备。尽管如此,迄今为止,丙二烯框架尚未被整合到用于不对称催化的配体中。由于丙二烯的功能与四面体碳或手性联芳基不同,因此它们可能会产生互补的手性环境。这项研究表明,光学活性的、C(2)-对称丙二烯的双膦氧化物可以催化SiCl(4)加成到内消旋环氧化物上,并具有高对映选择性。环氧化物的打开可能涉及路易斯酸性、阳离子(双膦氧化物)SiCl(3) 络合物的生成。观察到高不对称诱导的事实表明丙二烯可能代表了开发不对称合成配体和催化剂的新平台。