High 1,2-Asymmetric Induction in Radical Reactions: Radical Addition to<i>γ</i>-Hydroxy<i>α</i>,<i>β</i>-Unsaturated Carboxylic Esters and Sulfones
作者:Katsuyuki Ogura、Akio Kayano、Motohiro Akazome
DOI:10.1246/bcsj.70.3091
日期:1997.12
High 1,2-asymmetric induction was realized by the addition of a 1-hydroxy-1-methylethyl radical to conformationally flexible (E)-γ-hydroxy α,β-unsaturated carboxylic esters and sulfones (1 and 2, respectively). Upon the irradiation (> 290 nm) of (E)-1 and benzophenone in 2-propanol, the 1-hydroxy-1-methylethyl radical was generated in situ and added to (E)-1 with high anti-stereoselectivity. The bulkier
通过向构象灵活的 (E)-γ-羟基 α,β-不饱和羧酸酯和砜(分别为 1 和 2)添加 1-羟基-1-甲基乙基自由基,实现了高 1,2-不对称诱导。在 (E)-1 和二苯甲酮在 2-丙醇中照射 (> 290 nm) 后,原位生成 1-羟基-1-甲基乙基自由基并以高抗立体选择性添加到 (E)-1 中。(E)-1的γ-烷基越大,选择性越高。类似地,(E)-1 和 (E)-2 的乙酸酯的自由基加成以反方式立体选择性地进行,而 (Z)-2 表现出顺式立体选择性。讨论了这些立体选择性自由基加成的机制。