Mechanistic studies of pyrene-sensitized decomposition of p-butylphenyl azide: generation of nitrene radical anion through a sensitizer-mediated electron transfer from amines to the azide

Abstract

Pyrene-sensitized photolysis of p-butylphenyl azide (1) in acetonitrile containing diethylamine (DEA) gave a mixture of the 3H-azepine (2) and p-butylaniline (3). In order to reveal the mechanism of the formation of these photoproducts, the effects of the DEA or sensitizer concentration, solvents and various additives on the product distribution have been examined. Thus, it is proposed that the azepine 2 mainly originates from the singlet nitrene formed through the energy transfer from excited pyrene to the azide 1, while the one-electron reduction of 1 with the pyrene radical anion produced through the electron transfer from DEA to singlet excited pyrene is involved in the formation of the aniline 3.