Photoinduced Site-Selective Aryl C-H Borylation with Electron-Donor-Acceptor Complex Derived from B[sub.2]Pin[sub.2] and Isoquinoline

• Published in: Molecules (Basel, Switzerland) Switzerland), 2024-04, Vol.29 (8)
• Main Authors: Li, Manhong, Deng, Yi-Hui, Chang, Qianqian, Li, Jinyuan, Wang, Chao, Wang, Leifeng, Sun, Tian-Yu
• Format: Article
• Language: English
• Subjects: Chemical tests and reagents
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules29081783

Due to boron’s metalloid properties, aromatic boron reagents are prevalent synthetic intermediates. The direct borylation of aryl C-H bonds for producing aromatic boron compounds offers an appealing, one-step solution. Despite significant advances in this field, achieving regioselective aryl C-H bond borylation using simple and readily available starting materials still remains a challenge. In this work, we attempted to enhance the reactivity of the electron-donor-acceptor (EDA) complex by selecting different bases to replace the organic base (NEt[sub.3]) used in our previous research. To our delight, when using NH[sub.4]HCO[sub.3] as the base, we have achieved a mild visible-light-mediated aromatic C-H bond borylation reaction with exceptional regioselectivity (rr > 40:1 to single isomers). Compared with our previous borylation methodologies, this protocol provides a more efficient and broader scope for aryl C-H bond borylation through the use of N-Bromosuccinimide. The protocol’s good functional-group tolerance and excellent regioselectivity enable the functionalization of a variety of biologically relevant compounds and novel cascade transformations. Mechanistic experiments and theoretical calculations conducted in this study have indicated that, for certain arenes, the aryl C-H bond borylation might proceed through a new reaction mechanism, which involves the formation of a novel transient EDA complex.