Synthesis of 8-Oxabicyclo[3.2.1]octanes by TiCl4-Mediated Reactions of 3-Alkoxycyclobutanones and Allenylsilanes
作者:Jun-ichi Matsuo、Tatsuo Onnagawa、Mizuki Yamazaki、Tomoyuki Yoshimura
DOI:10.1055/s-0037-1611276
日期:2018.12
1-Substituted allenylsilanes reacted with 3-alkoxycyclobutanones in the presence of TiCl4 to afford 8-oxabicyclo[3.2.1]octan-3-ones stereoselectively. Nucleophilic attack of allenylsilanes to a 1,4-zwitterionic intermediate formed from 3-alkoxycyclobutanones and TiCl4 followed by 1,2-silyl migration, five-membered cyclization with an alkoxy group, and seven-membered cyclization of titanium enolate
1-取代的烯丙基硅烷在 TiCl4 存在下与 3-烷氧基环丁酮反应,立体选择性地得到 8-氧杂双环[3.2.1]辛烷-3-酮。提出了烯基硅烷对由 3-烷氧基环丁酮和 TiCl4 形成的 1,4-两性离子中间体的亲核攻击,然后是 1,2-甲硅烷基迁移、具有烷氧基的五元环化和烯醇钛的七元环化。氘化和一锅 Peterson 烯化表明在环化为 8-氧杂双环 [3.2.1] 辛烷骨架后形成了烷基钛物种。