Metal-Free Arylation of Benzothiophenes at C4 by Activation as their Benzothiophene S -Oxides
Metal-Free Arylation of Benzothiophenes at C4 by Activation as their Benzothiophene S -Oxides
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通过活化作为苯并噻吩 S 氧化物对苯并噻吩在 C4 处进行无金属芳基化
DOI：
10.1002/ange.202302418
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发表时间：
2023
影响因子：
--
通讯作者：
Bisht R
中科院分区：
文献类型：
--
作者：
Bisht R
苯并噻吩，通过氧化成相应的S-氧化物而活化，与苯酚进行C-H/C-H-型偶联，得到C4芳基化产物。虽然苯并噻吩的C3处的吸电子基团很重要，但该方法在没有导向基团和金属催化剂的情况下操作，从而使其与敏感官能团（例如卤化物和甲酰基）相容。量子化学计算表明，一个正式的逐步机制，涉及杂裂解的芳氧基硫物种，得到相应的苯并噻吩和苯氧鎓阳离子的π-配合物。随后将苯氧鎓阳离子加成到苯并噻吩的C4位置比加成到C3位置更有利;福井函数预测主要的区域异构体在C3和C4之间更富电子的位置形成。苯并噻吩产物的各种选择性操作展示了无金属芳基化过程的合成效用。
Benzothiophenes, activated by oxidation to the correspondingS‐oxides, undergo C−H/C−H‐type coupling with phenols to give C4 arylation products. While an electron‐withdrawing group at C3 of the benzothiophene is important, the process operates without a directing group and a metal catalyst, thus rendering it compatible with sensitive functionalities—e.g. halides and formyl groups. Quantum chemical calculations suggest a formal stepwise mechanism involving heterolytic cleavage of an aryloxysulfur species to give a π‐complex of the corresponding benzothiophene and a phenoxonium cation. Subsequent addition of the phenoxonium cation to the C4 position of the benzothiophene is favored over the addition to C3; Fukui functions predict that the major regioisomer is formed at the more electron‐rich position between C3 and C4. Varied selective manipulation of the benzothiophene products showcase the synthetic utility of the metal‐free arylation process.