On the Origins of Diastereoselectivity in the Alkylation of Enolates Derived from <i>N</i>-1-(1′-Naphthyl)ethyl-<i>O</i>-<i>tert</i>-butylhydroxamates: Chiral Weinreb Amide Equivalents
作者:Stephen G. Davies、Christopher J. Goodwin、David Hepworth、Paul M. Roberts、James E. Thomson
DOI:10.1021/jo902499s
日期:2010.2.19
The stereochemical outcome observed upon alkylation of enolates derived from N-1-(1′-naphthyl)ethyl-O-tert-butylhydroxamates (chiral Weinreb amide equivalents) may be rationalized by a chiral relay mechanism. Deprotonation with KHMDS leads to a nonchelated (Z)-enolate in which the oxygen atoms adopt an anti-periplanar conformation. The configuration of the N-1-(1′-naphthyl)ethyl group dictates the
的立体化学结果在从衍生的烯醇化物烷基化观察Ñ -1-(1'-萘基)乙基- ø -叔-butylhydroxamates(手性Weinreb酰胺等同物)可以通过手性继电器机构合理化。用KHMDS进行去质子化反应会生成非螯合的(Z)-烯醇酸酯,其中氧原子采用反周平面构象。所述的配置Ñ -1-(1'-萘基)乙基使然的的构象ø -叔丁基团和由相邻的棱锥形的氮原子通过的结构。高度非对映烯醇烷基化然后进行抗既笨重的叔-丁基(空间驱动)和N-孤对(空间电子驱动)。