Photochemical Cross-Organoboron Coupling of Heteroaryl and Alkyl Boronic Acids and Esters

Abstract

The Suzuki–Miyaura cross-coupling reaction is a cornerstone of C–C bond formation. However, heteroaryl boronic acids such as pyridyl and quinolyl derivatives remain challenging nucleophiles due to facile protodeboronation. Strategies enabling these substrates are limited to C(sp2)–C(sp2) formation. Efficient and modular C(sp2)–C(sp3) cross-coupling methods that directly employ these substrates remain underdeveloped. Here, we report a cross-organoboron platform that enables direct C(sp2)–C(sp3) bond formation from heteroaryl and alkyl organoboron reagents under visible-light irradiation using Ag2O/TiO2 nanoparticles (NPs). The two organoboron reagents undergo distinct Ag2O NP activations: alkyl boronates undergo single-electron photo-oxidation to generate alkyl radicals while arylboronates undergo transmetalation. Importantly, this method tolerates protodeboronation-prone pyridyl, quinolyl, α-heteroaryl boronic acids, and (hetero)aryl halide-containing substrates, including aryl iodides. High-throughput evaluation across 161 pharmaceutically relevant organoboron substrates identified 113 detectable couplings, and representative examples were validated at preparative scale. This work establishes photochemical cross-organoboron coupling as a complementary approach to classical transition-metal-catalyzed coupling and expands the accessible chemical space of heteroaryl organoboron reagents.