Transformation photochimique de pyridines et 1,2-diazépines

Bringing 1,2-diazepine back to center stage. This article traces the major milestones that led to the development of a one-pot, standardized protocol for the conversion of pyridines into 1,2-diazepines. By implementing a photochemical rearrangement discovered in the late 1960s by Jacques Streith into a multistep process, the ring expansion of pyridines through nitrogen atom insertion was achieved. These still little-known molecules were subsequently subjected to several transformations. Finally, mechanistic experiments support the initial hypotheses proposed nearly 60 years ago. Keywords : 1,2-Diazepine, pyridine, heterocycle, photochemistry, dearomatization.