Evidence for cyclic bromonium ion transfer in electrophilic bromination of alkenes: Reaction of ω-alkenyl glycosides with aqueous N-bromosuccinimide
作者:Robert Rodebaugh、Bert Fraser-Reid
DOI:10.1016/s0040-4020(96)00349-3
日期:1996.5
that intermolecular Br+ transfer from a cyclic bromonium ion to an alkene occurs readily and can indeed overwhelm alternative reaction pathways. In the course of a study to determine which ω-alkenyl glycosides could serve as glycosyl donors, it was found that upon treatment with N-bromosuccinimide (NBS) in aqueous acetonitrile, under conditions in which an n-pentenyl glycoside underwent oxidative hydrolysis
提供了证据来支持分子间Br +的理论从环溴离子转移到烯烃的转移很容易发生,并且确实会淹没其他反应途径。在确定哪些ω-烯基糖苷可以用作糖基供体的研究过程中,发现在N-溴丁二酰亚胺(NBS)在乙腈水溶液中处理的条件下,对正戊烯基糖苷进行氧化水解为相应的半缩醛,烯丙基,丁烯基和己烯基类似物产生了溴代醇加成产物。进一步发现,当制造戊烯基和己烯基类似物竞争不足量的NBS时,前者反应了,而后者显然没有改变。但是,两者均以相似的速率独立反应。另外,发现该现象是浓度依赖性的。这些结果与分子间,+从环溴离子到烯烃。