Photocatalyst-Free Four-Component Synthesis of 1,3,2-Diazaboroles through the Dual Reactivity of Diarylboryl Radicals.

1,3,2-Diazaboroles are valuable boron-nitrogen heterocycles with tunable electronic properties and broad potential applications. Their synthesis still largely relies on electrophilic organoboron reagents in combination with preorganized N,N-bidentate substrates or prefunctionalized precursors, which constrains structural diversity and functional group tolerance. Herein, we report a visible-light-induced, photocatalyst-free four-component reaction for the convergent synthesis of 1,3,2-diazaboroles. Distinct from conventional strategies, this radical pathway provides a fundamentally different approach with broad substrate scope. Photoinduced self-quenching of quinoxalinones enables the in situ generation of diarylboryl radicals, without an external photocatalyst. This work extends diarylboryl radical chemistry to otherwise inert alkyl chlorides and selected fluorinated substrates while integrating previously independently studied organohalide activation with B,N-heterocycle construction into a unified, sequentially orchestrated reaction manifold, representing a significant advance in neutral diarylboryl radical chemistry.