Intramolecular Bromonium Ion Assisted Epoxide Ring-Opening: Capture of the Oxonium Ion with an Added External Nucleophile
作者:Karl J. Bonney、D. Christopher Braddock、Andrew J. P. White、Muhammad Yaqoob
DOI:10.1021/jo101617h
日期:2011.1.7
bromonium ion-assisted epoxide ring-opening using N-bromosuccinimide via a presumed oxonium ion that is subject to stereospecific, nonregioselective capture with added external nucleophiles producing novel bicyclo[4.2.1] and bicyclo[3.3.1] ethers. Carboxylic acids (as catalyzed by tetramethylguanidine), alcohols, water, and halides can all function as effective nucleophiles. Stereospecific direct opening
9-氧杂双环[6.1.0] non-4-ene(1)通过N-溴丁二酰亚胺经推测的氧离子经历分子内溴离子辅助的环氧基开环反应,该氧离子可进行立体有择,非区域选择性的捕获,并通过添加外部亲核试剂产生新的双环[4.2.1]和双环[3.3.1]醚。羧酸(由四甲基胍催化),醇,水和卤化物都可以用作有效的亲核试剂。溴离子与羧酸的立体定向直接打开是一个竞争性过程,其中高稀释度不利于该途径。卤素诱导的同位素13个C NMR位移(Δδ ç溴1.3-1.9 ppb的;Δδ Ç发现Cl(8.6-8.7 ppb)在明确鉴定含卤素的碳中最有用,并且这些13 C NMR位移的相关性使得可以容易地分配非对映异构结构。加合物的结构部6b,图6c,图7b,图7c,7d中,和图8a - d都是由X-射线晶体学阐明。