Chiral oxazolidines acting as transient hydroxyalkyl-functionalized N-heterocyclic carbenes: an efficient route to air stable copper and gold complexes for asymmetric catalysis
作者:Delphine Pichon-Barré、Ziyun Zhang、Aël Cador、Thomas Vives、Thierry Roisnel、Olivier Baslé、Lucie Jarrige、Luigi Cavallo、Laura Falivene、Marc Mauduit
DOI:10.1039/d2sc02908a
日期:——
imidazolinium salts. Acting as transient chiral diamino N-heterocyclic carbenes (NHCs), these oxazolidines allowed the efficient formation of well-defined copper(I) and gold(I) hydroxyalkyl-NHC complexes, which could be isolated, for the first time, as air stable complexes after silica gel chromatography. Interestingly, X-ray analysis of gold complexes revealed that the hydroxyl-function is not chelated
由手性羟烷基官能化咪唑啉盐以几乎定量的收率合成光学纯的恶唑烷。作为瞬态手性二氨基 N-杂环卡宾 (NHC),这些恶唑烷可以有效地形成明确定义的铜 ( I ) 和金( I) 羟基烷基-NHC 配合物,这是第一次在硅胶色谱后作为空气稳定的配合物分离出来。有趣的是,金配合物的 X 射线分析表明羟基官能团没有与金属螯合。计算研究表明,环化产生恶唑烷和 O-H 键消除形成瞬态卡宾(在配位之前)都是通过协同机制发生的。新型手性铜催化剂以及单独的恶唑烷(不含铜)在不对称共轭加成和烯丙基烷基化中表现出优异的性能,具有高区域和对映选择性(高达 99% ee)。