New Radical Borylation Pathways for Organoboron Synthesis Enabled by Photoredox Catalysis
New Radical Borylation Pathways for Organoboron Synthesis Enabled by Photoredox Catalysis
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光氧化还原催化实现有机硼合成的新自由基硼化途径
DOI：
10.1002/anie.201915619
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发表时间：
2020-05-26
影响因子：
16.6
通讯作者：
Wang, Yi-Feng
中科院分区：
文献类型：
--
作者：
Qi, Jing;Zhang, Feng-Lian;Wang, Yi-Feng
使用N-杂环卡宾（NHC）-BH 3配合物作为硼基自由基前体的自由基硼化反应已经成为有机硼组装的重要合成工具。然而，大多数报道的方法仅限于涉及特定烯烃和炔的碳-和/或硼氢化的反应模式。此外，NHC-硼基自由基的产生主要依赖于在自由基引发剂的帮助下的氢原子提取。报道了一种独特的自由基产生方法，以及光氧化还原催化实现的NHC-硼基自由基的反应途径。NHC-硼基自由基通过单电子氧化产生，随后与原位产生的自由基阴离子发生交叉偶联，得到偕-二氟烯丙基硼酸酯。以氰基芳烃为芳基化组分，实现了光氧化还原催化下烯烃的芳基硼化反应，并由此合成了精细的有机硼。机理研究证实了NHC-硼基自由基的氧化形成通过一个单电子转移途径。
Radical borylation using N-heterocyclic carbene (NHC)-BH3 complexes as boryl radical precursors has emerged as an important synthetic tool for organoboron assembly. However, the majority of reported methods are limited to reaction modes involving carbo- and/or hydroboration of specific alkenes and alkynes. Moreover, the generation of NHC-boryl radicals relies principally on hydrogen atom abstraction with the aid of radical initiators. A distinct radical generation method is reported, as well as the reaction pathways of NHC-boryl radicals enabled by photoredox catalysis. NHC-boryl radicals are generated via a single-electron oxidation and subsequently undergo cross-coupling with the in-situ-generated radical anions to yield gem-difluoroallylboronates. A photoredox-catalyzed radical arylboration reaction of alkenes was achieved using cyanoarenes as arylating components from which elaborated organoborons were accessed. Mechanistic studies verified the oxidative formation of NHC-boryl radicals through a single-electron-transfer pathway.