phenylglycine derived chiral NHC was shown to give the best Ir catalyst and it also gave the maximum ee compared to catalysts prepared from other NHCs in this series. The opposite enantiomer of the reduction product was always obtained while using the Ir complex bearing a valine based NHC. The yields were consistently high with a variety of imine substrates having different steric and electronic demands
摘要使用一系列手性半三明治
铱配合物,研究了
亚胺对映体选择性还原为相应的手性仲胺。这些配合物中的手性N-杂环卡宾(NHC)
配体是由易于获得的天然
氨基酸合成的。廉价的苯基
硅烷被用作方便的氢供体。在优化的条件下,Ir-NHC复合物可以降低酮
亚胺的收率,尽管对映体过量(ee)适中。与由该系列其他NHC制备的催化剂相比,苯基甘
氨酸衍生的手性NHC被证明可提供最佳的Ir催化剂,并且也可提供最大的ee。当使用带有基于缬
氨酸的NHC的Ir配合物时,总是获得还原产物的相反对映异构体。