Difluoromethylation of Unactivated Alkenes Using Freon-22 through Tertiary Amine-Borane-Triggered Halogen Atom Transfer,Journal of the American Chemical Society

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Difluoromethylation of Unactivated Alkenes Using Freon-22 through Tertiary Amine-Borane-Triggered Halogen Atom Transfer
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2022-07-27 , DOI: 10.1021/jacs.2c05356
Zhi-Qi Zhang _{1,

2} , Yue-Qian Sang ₃ , Cheng-Qiang Wang ₂ , Peng Dai ₂ , Xiao-Song Xue ₃ , Jared L Piper ₄ , Zhi-Hui Peng ₄ , Jun-An Ma _{1,

5} , Fa-Guang Zhang _{1,

5} , Jie Wu _{1,

2}

Affiliation

The application of abundant and inexpensive fluorine feedstock sources to synthesize fluorinated compounds is an appealing yet underexplored strategy. Here, we report a photocatalytic radical hydrodifluoromethylation of unactivated alkenes with an inexpensive industrial chemical, chlorodifluoromethane (ClCF₂H, Freon-22). This protocol is realized by merging tertiary amine-ligated boryl radical-induced halogen atom transfer (XAT) with organophotoredox catalysis under blue light irradiation. A broad scope of readily accessible alkenes featuring a variety of functional groups and drug and natural product moieties could be selectively difluoromethylated with good efficiency in a metal-free manner. Combined experimental and computational studies suggest that the key XAT process of ClCF₂H is both thermodynamically and kinetically favored over the hydrogen atom transfer pathway owing to the formation of a strong boron–chlorine (B–Cl) bond and the low-lying antibonding orbital of the carbon–chlorine (C–Cl) bond.

中文翻译：

通过叔胺-硼烷触发的卤素原子转移使用 Freon-22 对未活化烯烃进行二氟甲基化

应用丰富且廉价的氟原料来源来合成含氟化合物是一种有吸引力但尚未充分探索的策略。在这里，我们报告了用廉价的工业化学品氯二氟甲烷（ClCF ₂ H，Freon-22）对未活化烯烃进行光催化自由基氢二氟甲基化。该协议是通过在蓝光照射下将叔胺结扎硼自由基诱导的卤素原子转移 (XAT) 与有机光氧化还原催化相结合来实现的。具有多种官能团以及药物和天然产物部分的广泛易于获得的烯烃可以以无金属的方式以良好的效率选择性地二氟甲基化。结合实验和计算研究表明，ClCF _{2的关键 XAT 过程}由于形成强的硼-氯（B-Cl）键和碳-氯（C-Cl）键的低位反键轨道，H在热力学和动力学上都优于氢原子转移途径。

更新日期：2022-07-27

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