Aerobic and Anaerobic Borylation of (Hetero)arenes Triggered by Visible-Light Irradiation

Organoboronate esters have attracted significant attention due to their broad utility in organic synthesis as versatile intermediates, as well as their relevance in medicinal chemistry and materials science. These environmentally benign building blocks can be readily transformed into a wide range of functional groups, enabling their application in the synthesis of advanced materials. In particular, heteroaryl boronates such as thiophene-derived esters are of special interest owing to their diverse applications, ranging from conjugated materials for organic electronics and LED devices to antimicrobial agents in medicinal chemistry.^[1]
Accordingly, the development of innovative and efficient synthetic strategies for their preparation remains highly desirable. Over the past decade, numerous methodologies based on transition-metal catalysis or metal-free approaches have been reported for the synthesis of organoboron derivatives and their subsequent functionalization.^[2] Among the available precursors, aryl halides stand out as ideal starting materials due to their low cost and widespread commercial availability. In this context, visible-light photoredox catalysis has emerged as a powerful strategy for the activation of aryl halides, enabling the generation of radical intermediates that can be efficiently trapped by boron-based nucleophiles to afford aryl boronate esters.^[3]
Herein, we report our latest results on the borylation of (hetero)aryl halides under anaerobic and aerobic mild conditions using an easy-to-handle gel nanoreactor. This photocatalyst-free protocol proceeds under visible-light irradiation at room temperature and in the presence of air, highlighting its operational simplicity and sustainability. Notably, the gel network provides a stabilizing microenvironment that enables a broad substrate scope.
References
[1] Neeve, E. C.; Geier, S. J.; Mkhalid, I. A. I.; Westcott, S. A.; Marder, T. B. Chem. Rev. 2016, 116, 9091.
[2] Hemming, D.; Fritzemeier, R.; Westcott, S. A.; Santos, W. L.; Steel, P. G. Chem. Soc. Rev. 2018, 47, 7477.
[3] Twilton, J.; Le, C.; Zhang, P.; Shaw, M. H.; Evans, R. W.; MacMillan, D. W. C. Nat. Rev. Chem. 2017, 1, 0052.