Sequestered Alkyllithiums: Why Phenyllithium Alone is Suitable for Betaine-Ylide Generation
作者:Qian Wang、Dariusz Deredas、Cyril Huynh、Manfred Schlosser
DOI:10.1002/chem.200390061
日期:2003.1.20
modification of the Wittig reaction is the alpha-lithiation of the lithium bromide coordinated ylide-aldehyde adduct (the so-called "P-betaine"). Only phenyllithium effects this deprotonation rapidly and cleanly. Alkyllithiums (in particular, butyl-, sec-butyl-, and tert-butyllithium) react only sluggishly and incompletely, being tied up in very stable mixed aggregates with the lithium alkoxide part
Wittig反应的反式选择性修饰的关键步骤是溴化锂配位的乙醛-醛加合物(所谓的“ P-甜菜碱”)的α-锂化。只有苯基锂才能快速,干净地实现该去质子化。烷基锂(特别是丁基,仲丁基和叔丁基锂)反应缓慢且不完全,它们与甜菜碱的锂醇盐部分固定在非常稳定的混合聚集体中。