Photoinduced radical addition of 4-alkyl-1,4-DHPs to vinyl azides

Abstract

An efficient and operationally simple protocol for the synthesis of ketones via photoinduced radical addition of 4-alkyl-1,4-dihydropyridines (1,4-DHPs) to vinyl azides is described. The reaction proceeds under blue light irradiation, demonstrating broad functional group tolerance and moderate to excellent yields across a range of substrates. Mechanistic studies, including radical-trapping experiments, light on/off control experiments, and detailed Hammett analysis, substantiate a radical pathway. The use of dual-parameter Hammett correlations (σ_mb and σ_JJ˙) provides strong evidence for a radical pathway and elucidates key kinetic features of the transformation. This work delivers both a practical synthetic method and a fundamental mechanistic understanding of this radical addition reaction.