First asymmetric nucleophilic displacement reactions on chiral α-substituted aldehyde hydrazones
作者:Dieter Enders、Ralf Maaßen、Jan Runsink
DOI:10.1016/s0957-4166(98)00205-5
日期:1998.6
The first asymmetric nucleophilic substitution reaction on racemic α-substituted aldehydes using enantiomerically pure hydrazines as chiral auxiliaries is presented. The diastereoselectivity of the process is achieved by a dynamic kinetic resolution via the 1:1 epimeric mixture of the substrate hydrazones. The a2-reactivity (Umpolung) of the α-substituted hydrazones is accomplished by complexation
提出了使用对映体纯的肼作为手性助剂对外消旋α-取代的醛进行的第一个不对称亲核取代反应。该方法的非对映选择性是通过底物hydr的1:1差向异构体混合物通过动态动力学拆分来实现的。在一个2的α取代的腙的-reactivity(极性转换)通过与路易斯酸络合完成。在这些条件下,数个碳亲核,硫亲和氧亲核试剂容易发生α-离去基团的取代,从而提供具有良好或优异的化学收率和低至中等非对映选择性的取代产物。描述了裂解手性助剂的两种方法。