8-Endo Cyclization of (Alkoxycarbonyl)methyl Radicals: Radical Ways for Preparation of Eight-Membered-Ring Lactones
作者:Eun Lee、Cheol Hwan Yoon、Tae Hee Lee、Sun Young Kim、Tae Joon Ha、Yong-suk Sung、Sang-Hyun Park、Sangyoub Lee
DOI:10.1021/ja980908d
日期:1998.8.1
Cyclization of (alkoxycarbonyl)methyl radicals generated from bromoacetates proceeds in the 8-endo mode to generate heptanolactones. Three distinct types of 8-endo/5-exo tandem radical cyclizations produce different bicyclic heptanolactones. In certain cases, intramolecular free-radical attack on the heptanolactone carbonyl group initiates further skeletal rearrangement. Ab initio calculations indicate
由溴乙酸酯生成的(烷氧基羰基)甲基自由基的环化以 8-endo 模式进行以生成庚内酯。三种不同类型的 8-endo/5-exo 串联自由基环化产生不同的双环庚内酯。在某些情况下,对庚内酯羰基的分子内自由基攻击会引发进一步的骨架重排。Ab initio 计算表明,8-endo 环化优于 5-exo 模式源于(烷氧基羰基)甲基自由基的构象偏差,有利于 Z-而不是 E-构象。