Photochemical Synthesis of 1-Propyl-3-phenylquinoxalin-2(1 <i>H</i> )-one: An Undergraduate Laboratory Experiment

Abstract 3-Arylquinoxaline-2(1H)-ones are significant scaffolds in medicinal chemistry due to their diverse biological and pharmacological activities, such as neuroprotective and anti-cancer activities. While photo-induced synthesis has emerged as a sustainable approach to these compounds, existing protocols often require expensive photocatalysts or inert atmospheres, which limited their integration into undergraduate curricula. This article presents a novel organic chemistry laboratory experiment describing the photocatalyst-free, photo-induced arylation of 3-phenyl-1-propylquinoxalin-2(1H)-one under ambient air. The reaction employs phenylhydrazine hydrochloride as a phenyl radical precursor and N,N-dimethylpyridin-4-amine (DMAP) as a base. Using a 50 W blue LED, the reaction is completed within 2 h, providing isolated yields of 71%–78% after purification by column chromatography. Through this comprehensive experiment, students gain hands-on experience in (1) Synthesis and purification; (2) Characterization; and (3) Conceptual integration. This laboratory protocol is highly accessible, employing commercially available reagents and mild reaction conditions. It addresses the gap in photochemical experiments for undergraduate students and serves as an eco-friendly supplement to the medicinal and organic chemistry curriculum.