Photocatalytic C–I Borylation via Halogen Bond-Enabled Electron Transfer: A Strategy for Generating Aryl Radicals from Haloarenes

Abstract

We report the development of triarylphenol-based photocatalysts that promote C–I bond borylation via halogen bonding (XB) interactions under visible-light irradiation. Traditional phenol system reactions often suffer from phenoxyl radical instability, limiting their catalytic utility. To overcome this issue, we designed sterically and electronically tuned triarylphenols that stabilize radical intermediates while maintaining high photoreactivity. Systematic evaluation revealed that 2,4,6-triphenylphenol efficiently facilitates photoinduced electron transfer (PET) and suppresses undesired side reactions such as phenol decomposition. The optimized reaction conditions enabled a broad substrate scope, showing efficient arylboronic ester formation. Density functional theory calculations confirmed the formation of XB complexes with charge-transfer character, providing mechanistic support for the PET pathway. This work shows the potential of rationally designed phenols as XB acceptors and offers a sustainable approach for C–I bond functionalization.