o-fluoro substituents results in an improvement to the reduction enantioselectivity, as does the replacement of a phenyl ring on the alkyne with a trimethylsilyl group. These effects are rationalized as resulting from a change in the steric properties of the aryl ring and the electronic properties of the alkyne which, when matched in the reduction transition state, combine within a “window” of substrate/catalyst
束缚
钌-TsDPEN配合物已用于催化一系列芳基/炔酮的不对称转移氢化反应。将邻位取代基引入底物的芳基环会导致对映选择性的逆转,而引入两个邻
氟取代基则会导致还原对映体选择性的提高,而取代基上的苯环也是如此。具有三甲基甲
硅烷基的
炔烃。这些效应是由于芳基环的空间性质和
炔烃的电子性质发生变化而合理化的,这些
炔烃在还原过渡态下匹配时,会在底物/催化剂匹配的“窗口”内结合,生成高分子量的产物ee。