摘要/Abstract
报道了一类新颖的可见光催化的1,6-烯炔参与的Kharasch加成反应. 该反应利用三氯溴甲烷和四溴化碳在光催化还原下能产生三卤代甲基自由基的特性, 实现其在fac-Ir(ppy)3与可见光作用下与1,6-烯炔发生Kharasch加成反应, 区域选择性地合成了具有环外双键以及季碳的1-茚酮衍生物, 产率中等至良好. 基于实验结果及文献报道, 提出了合理的反应机理, 涉及三卤代甲基自由基的原位形成、自由基引发的加成环化以及自由基交叉偶联等. 此外, 该反应具有底物普适性广、高官能团兼容性、100%原子利用率、条件温和、操作简便等优点, 从而为具有潜在应用价值的1-茚酮骨架的构建提供了一种绿色、温和且高效的合成策略, 符合绿色化学理念.
关键词: Kharasch加成, 可见光催化反应, 1,6-烯炔衍生物, 1-茚酮衍生物
A new visible-light-driven photocatalytic Kharasch-type addition of 1,6-enynes was reported. By using the characteristics of the in-situ-generation of trihalomethyl radicals from photocatalytic reduction of trichloromethane bromide and carbon tetrabromide, fac-Ir(ppy)3-catalyzed Kharasch-type addition of 1,6-enynes of these polyhalogenated hydrocarbon substrates at room temperature was conducted under visible-light irradiation, regioselectively affording 1-indanone derivatives with an exocyclic double bond and a quaternary carbon in moderate to good yields. Based on the experimental results and literature reports, a reasonable reaction mechanism was proposed, which involved the in-situ-generation of trihalomethyl radicals, radical-induced addition-cyclization and radical cross coupling. In addition, this protocol featured wide substrate scope, high functional group compatibility, 100% atomic utilization, and mild conditions as well as simple operation. It provides a green, mild, and efficient synthetic strategy for the construction of 1-indanone skeleton with potential application, which is consistent with the concept of green chemistry.
Key words: Kharasch-type addition, photocatalysis, 1,6-enynes, 1-indanones
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