高反应性试剂烯丙基卤化镁与α-取代的无环手性酮的加成具有高立体选择性。立体选择性无法通过常规立体化学模型进行分析,因为这些反应不符合这些模型的要求。相反,立体选择性是由于亲核试剂接近酮的最低能量构象的最容易接近的非对映面而产生的。预期具有高立体选择性,并且可以预测立体化学结果,其中构象偏向的酮具有空间上可区分的非对映面,其中只有一个面可进行亲核加成。酮的构象可以通过计算建模和在某些情况下通过 X 射线晶体学确定结构的组合来确定。
Reduction of α-hydroxy ketones with zinc horohydride afforded the -glycols in high stereoselectivity, while reduction of their α-(t-butyldiphenylsily)oxy derivatives with sodium bis(2-methoxyethoxy)aluminum hydride gave the isomeric . The structure-stereoselectivity relationship has been discussed.
Chelates as intermediates in nucleophilic additions to alkoxy ketones according to Cram's rule (cyclic model)
作者:Xiangning Chen、Edwin R. Hortelano、Ernest L. Eliel、Stephen V. Frye
DOI:10.1021/ja00031a036
日期:1992.2
Chelates have been considered intermediates in the often highly stereoselective reactions of α-alkoxy and similarly substituted ketones for over 30 years, 10 but without mechanistic evidence