Convergent and Stereoselective Synthesis of Trisubstituted <i>E</i>-Alkenyl Bromides and Iodides via β-Oxido Phosphonium Ylides
作者:David M. Hodgson、Tanzeel Arif
DOI:10.1021/ja8076999
日期:2008.12.10
β-Oxido phosphonium ylides, generated in situ from aldehydes and Wittigreagents [alkylidene(triphenyl)phosphoranes, other than ethylidene(triphenyl)phosphorane], react readily with electrophilic halogen sources to form predominantly or exclusively E-bromo- or iodosubstituted alkenes. The stereochemical outcome on halogenation is remarkably sensitive to alkylidene size [ethylidene(triphenyl)phosphorane
β-氧化鏻叶立德由醛和 Wittig 试剂 [亚烷基(三苯基)正膦,除亚乙基(三苯基)正膦外] 原位生成,容易与亲电子卤素源反应,主要或仅形成 E-溴或碘取代的烯烃。卤化的立体化学结果对亚烷基大小非常敏感 [亚乙基(三苯基)正膦具有高度的 Z 选择性]。