Recent Advances in Photochemical Transformations of Nitroarenes toward the Construction of N-Heterocycles

Abstract N-Heterocycles are fundamental structural motifs in pharmaceuticals, materials science, and dyes. As inexpensive and readily available bulk chemicals, nitroarenes serve as ideal starting materials for N-heterocycle synthesis. The development in photochemistry has opened new avenues for nitroarene activation, offering clean, mild, and highly selective reaction conditions. This review systematically summarizes recent advances in the photoinduced construction of N-heterocycles from nitroarenes. We categorize these transformations into two primary strategies based on nitroarene activation: direct excitation pathways, which include HAT-mediated synthesis of indazoles and acridines alongside excited-state [3+2] cycloadditions yielding indoles and isoxazolidines; and exogenous electron-initiated processes, featuring photoredox and EDA complex-mediated cyclizations for constructing benzimidazoles and fused piperidines. For each approach, we provide a detailed discussion of substrate scope, reaction mechanisms, regioselectivity, and functional group compatibility and outline the advantages and limitations. This comprehensive overview aims to inspire further innovation in leveraging nitroarenes for the sustainable synthesis of complex nitrogen-containing architectures.