Department of Chemistry, The Hong Kong University of Science and Technology Clear Water Bay, Kowloon, Hong Kong SAR, P. R. China.
Chemistry. 2023 Feb 10;29(9):e202203053. doi: 10.1002/chem.202203053. Epub 2022 Dec 27.
Air-stable amine- and phosphine-boranes are discovered as donors to integrate with pyridinium acceptor for generating photoactive electron-donor-acceptor (EDA) complexes. Experimental results and DFT calculations suggest a dihydrogen bond bridging the donor and acceptor. Irradiating the EDA complex enables an intra-complex single electron transfer to give a boron-centered radical for dehydrogenative borylation with no need of external photosensitizer and radical initiator. The deprotonation of Wheland-like radical intermediate rather than its generation is believed to determine the good ortho-selectivity based on DFT calculations. A variety of α-borylated pyridine derivatives have been readily synthesized with good functional group tolerance.
研究发现，稳定的胺基和膦基硼烷可作为供体与吡啶阳离子受体结合，生成光活性的给体-受体（EDA）配合物。实验结果和密度泛函理论（DFT）计算表明，氢键桥接供体和受体。EDA 配合物经光照后，可在无需外加光敏剂和自由基引发剂的情况下，通过内配合物单电子转移，生成硼中心自由基，从而进行脱氢硼化反应。根据 DFT 计算，反应的区域选择性取决于 Wheland 自由基中间体的去质子化而非生成。该方法具有良好的官能团容忍性，可方便地合成各种α-硼化吡啶衍生物。
