上海
化学深耕堂
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长按识别丨直达原文
深耕点评
日本北海道大学/名古屋大学Hiroki Hayashi团队通过酮介导的碱促光化学活化，使氟仿直接生成三氟甲基自由基，实现烯烃、炔烃及芳香化合物的自由基三氟甲基化。该体系无需外加氧化还原试剂，可进一步构建酮催化反应，并用于克级合成、复杂分子后期修饰和大宗化学品增值转化。
深耕亮点：
1）实现氟仿的温和自由基活化。氟仿脱质子形成CF₃⁻后被酮羰基捕获，所得烷氧负离子经光激发裂解释放CF₃·，使氟仿能够直接作为自由基三氟甲基源。
2）形成酮介导的光催化循环。光裂解同步产生CF₃·和酮自由基阴离子，二者分别参与自由基加成与后续电子转移，使酮得以再生，并将化学计量活化拓展为催化反应。
3）适用于多类自由基三氟甲基化反应。该体系可实现烯烃和炔烃的氢三氟甲基化，也可拓展至芳香化合物的氧化三氟甲基化，并兼容多种官能团及结构复杂的生物活性分子。
4）具备一定的合成应用能力。代表性反应可进行克级放大，复杂分子能够完成后期三氟甲基化；氟仿还可与大宗烯烃原料共同转化为高价值含氟化合物，酮介体可回收再用。
5）机理研究明确了关键光活化物种。实验与计算结果共同支持烷氧负离子直接吸光并发生C–C键均裂，同时表明自由基中间体的电子性质会影响后续单电子转移或自由基偶联过程。
Abstract
Fluoroform is an ideal trifluoromethyl source in synthetic chemistry due to its low cost, low toxicity, and high potential for greenhouse-gas valorization. However, the use of fluoroform has been largely limited to the generation of trifluoromethyl anions or metal-bound species; direct access to the trifluoromethyl radical remains elusive, despite the broad applicability of radical trifluoromethylation for preparing medicinally important compounds. Here, we report a method for radical trifluoromethylation using fluoroform by leveraging the reactivity of ketones in combination with a Brønsted base under photoirradiation. The ketone-mediated photochemical activation provides access to the trifluoromethyl radical from fluoroform via a photoexcited alkoxide intermediate without exogenous redox reagents, enabling radical trifluoromethylation of alkenes and arenes under mild conditions. The developed system is amenable to a photocatalytic protocol, late-stage trifluoromethylation of complex molecules, and upgrading bulk chemicals into high-value trifluoromethylated compounds.
作者信息
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https://yagilabnagoya.
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hirokihayashi/
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