Photoinduced metal-free borylation of aryl halides catalysed by an in situ formed donor-acceptor complex

• Published in: Chemical science (Cambridge) Vol. 13; no. 17; pp. 4909 - 4914
• Main Authors: Li, Manhong, Liu, Siqi, Bao, Haoshi, Li, Qini, Deng, Yi-Hui, Sun, Tian-Yu, Wang, Leifeng
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 04.05.2022; The Royal Society of Chemistry
• Subjects: Aromatic compounds; Chemistry; Coordination compounds; Functional groups; Halides; Hydrogen bonds; Organoboron compounds; Photochemistry; Reducing agents; Single electrons
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/d2sc00552b

Organoboron compounds are very important building blocks which can be applied in medicinal, biological and industrial fields. However, direct borylation in a metal free manner has been very rarely reported. Herein, we described the successful direct borylation of haloarenes under mild, operationally simple, catalyst-free conditions, promoted by irradiation with visible light. Mechanistic experiments and computational investigations indicate the formation of an excited donor-acceptor complex with a -3.12 V reduction potential, which is a highly active reductant and can facilitate single-electron-transfer (SET) with aryl halides to produce aryl radical intermediates. A two-step one-pot method was developed for site selective aromatic C-H bond borylation. The protocol's good functional group tolerance enables the functionalization of a variety of biologically relevant compounds, representing a new application of aryl radicals merged with photochemistry.