Investigation of Bis(tributyltin)-Initiated Free Radical Cyclization Reactions of 4-Pentenyl Iodoacetates
作者:Junhua Wang、Chaozhong Li
DOI:10.1021/jo0109568
日期:2002.2.1
free radical cyclization to generate gamma-iodoheptanolactones which easily underwent intramolecular nucleophilic substitution to form bicyclic acylium species (7) as the key intermediate. Subsequent attack by iodide ion furnished gamma-lactones while attack by hydroxide ion gave the tetrahydrofuran derivatives.
4-戊烯基碘乙酸酯(1)在80摄氏度下的双(三丁基锡)引发的原子转移环化反应导致高产率形成5-(3-碘丙基)-取代的二氢-2(3H)-呋喃酮(3) 。以BF3 * Et2O为催化剂,反应在室温下进行,得到相应的γ-碘庚庚醇内酯(2),经水处理可进一步转化为3-(四氢-2-呋喃基)丙酸(6)。碳酸氢钠 推测该反应机理是8-内基自由基环化以生成γ-碘庚庚醇内酯,其容易经历分子内亲核取代以形成双环基物种(7)作为关键中间体。随后被碘离子侵蚀而产生的γ-内酯,而被氢氧根离子侵蚀得到了四氢呋喃衍生物。