Factors Affecting Migration of Tertiary Alkyl Groups in Reactions of Alkylboronic Esters with Bromomethyllithium
作者:Mark C. Elliott、Keith Smith、D. Heulyn Jones、Ajaz Hussain、Basil A. Saleh
DOI:10.1021/jo4000459
日期:2013.4.5
be of great potential for the formation of quaternary carbon centers but often give poor yields/conversions. Calculations and experimental evidence show that tert-alkyl groups migrate less effectively than other types of alkyl group in such reactions and that O-migration competes. Furthermore, slow/incomplete capture of the bromomethyl reagent by the boronic ester is a problem in more hindered systems
溴甲基锂与叔烷基硼酸酯的反应对于形成季碳中心可能具有巨大潜力,但通常收率/转化率很低。计算和实验证据表明,叔烷基基团比在这样的反应和其它类型的烷基的更小有效迁移ö移民竞争。此外,在更受阻的系统中,硼酸酯无法缓慢/不完全捕获溴甲基试剂是一个问题,另外的竞争性反应(可能在溴甲基硼酸酯种类上进行Li-Br交换)也会导致迁移产物的收率降低。基于此,已经设计了实验方案,其中竞争反应被大大抑制,从而导致针对多种底物的转化产物的转化率更高。