A rapid injection NMR study of the chelation controlled Mukaiyama aldol addition: TiCl4 versus LiClO4 as the Lewis acid
作者:Manfred T Reetz、Burkhard Raguse、Charles F Marth、Helmut M Hügel、Thorsten Bach、David N.A Fox
DOI:10.1016/0040-4020(92)80024-a
日期:1992.7
The concept of chelation controlled addition to chiral alkoxy aldehydes using Lewis acids and mild C-nucleophiles has been extended to include cyclopropylation. The mechanism of the TiCl4-mediated chelation controlled addition of enolsilanes and allylsilanes to chiral α-alkoxy aldehydes has been studied by rapid injection NMR techniques. Accordingly, an acyclic transition state is involved in which
使用路易斯酸和温和的C-亲核试剂对手性烷氧基醛进行螯合控制加成的概念已扩展为包括环丙基化。通过快速注入NMR技术研究了TiCl 4介导的烯醇硅烷和烯丙基硅烷向手性α-烷氧基醛的螯合控制加成的机理。因此,涉及其中甲硅烷基不迁移至羰基氧原子的无环过渡态。相反,LiClO 4是有效的路易斯酸(过量或催化量),其诱导螯合控制的基团转移类型的醛醇加成。