Generation of Phosphoranyl Radicals via Photoredox Catalysis Enables Voltage-Independent Activation of Strong C-O Bonds.
Generation of Phosphoranyl Radicals via Photoredox Catalysis Enables Voltage-Independent Activation of Strong C-O Bonds.
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DOI：
10.1021/acscatal.8b03592
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发表时间：
2018-10
期刊：
影响因子：
12.9
通讯作者：
Erin E. Stache;A. Ertel;Rovis Tomislav;A. Doyle
中科院分区：
文献类型：
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作者：
Erin E. Stache;A. Ertel;Rovis Tomislav;A. Doyle
尽管醇和羧酸作为官能团在有机分子中普遍存在，并且有可能作为自由基前体，但C-O键仍然难以激活。我们报道了一种通过光氧化还原催化直接从这些普遍存在的官能团中获得烷基和酰基自由基的合成策略。该方法利用磷酰自由基的独特反应活性，由磷自由基阳离子与氧中心亲核试剂之间的极性/SET交叉产生。我们证明了苯基醇还原成相应的苯基自由基的反应活性，其末端H原子被捕获以提供脱氧产物。使用相同的方法，我们证明了合成通用酰基自由基的途径，这使得芳香族和脂肪族羧酸还原为具有特殊化学选择性的相应醛。该方法还通过分子内酰基环化反应将羧酸转化为杂环和环酮，一步形成C-O、C-N和C-C键。
Despite the prevalence of alcohols and carboxylic acids as functional groups in organic molecules and the potential to serve as radical precursors, C-O bonds remain difficult to activate. We report a synthetic strategy for direct access to both alkyl and acyl radicals from these ubiquitous functional groups via photoredox catalysis. This method exploits the unique reactivity of phosphoranyl radicals, generated from a polar/SET crossover between a phosphine radical cation and an oxygen-centered nucleophile. We show the desired reactivity in the reduction of benzylic alcohols to the corresponding benzyl radicals with terminal H atom trapping to afford the deoxygenated products. Using the same method, we demonstrate access to synthetically versatile acyl radicals, which enables the reduction of aromatic and aliphatic carboxylic acids to the corresponding aldehydes with exceptional chemoselectivity. This protocol also transforms carboxylic acids to heterocycles and cyclic ketones via intramolecular acyl radical cyclizations to forge C-O, C-N, and C-C bonds in a single step.