New Umpolung Catalysts: Reactivity and Selectivity of Terpenol-Based Lithium Phosphonates in Enantioselective Benzoin-Type Couplings
作者:Anca Gliga、Helge Klare、Maria Schumacher、Francis Soki、Jörg M. Neudörfl、Bernd Goldfuss
DOI:10.1002/ejoc.201001295
日期:2011.1
Two new classes of terpenol-based lithium phosphonates, i.e. phenylfenchyl phosphonates and 2,2'-biphenyldiylbis(terpenyl) phosphonates, are employed as umpolung catalysts for the enantioselective cross benzoin coupling. The structural characteristics of the phosphonates were investigated by means of X-ray, 31 P-NMR analyses as well as DFT computations. The chiral lithium phosphonates were found to
两类新的基于萜烯醇的膦酸锂,即苯基芬基膦酸和 2,2'-联苯基二基双(萜)膦酸,被用作对映选择性交叉安息香偶合的 umpolung 催化剂。通过X-射线、31 P-NMR分析以及DFT计算研究了膦酸酯的结构特征。发现手性膦酸锂以高达 54% ee 的对映选择性催化交叉安息香偶合。对于苯基芬基膦酸酯,催化剂的反应性高度依赖于苄基位置的取代基。苄基 >CH 2 到 >C(CF 3 ) 2 的改性使产率从 19% 显着增加到 92%。对于苯基芬基膦酸酯预催化剂,苄基 >CH 2 基团被 >