Photoinduced formation and reaction of benzalaniline radical anions: comparison with the radiation-induced reaction

Abstract

Photoirradiation of benzalaniline ( 1) and its derivatives in a tetrahydrofuran (THF) solution yielded a THF adduct regioselectively. The reaction efficiency is strongly dependent on the substituent of both benzene rings, and photoexcitation of the intramolecular charge transfer (CT) band is effective for the product formation. In the case of the 4′-CN derivative, this reaction appears to proceed via the radical anion, the transient absorption of which was clearly observed upon the irradiation of a 2-methyltetrahydrofuran matrix at 77 K. Thus the CT excited state may be quenched by THF to form the radical anion of 1. The following reaction of the radical anion was also studied by γ-ray irradiation and pulse radiolysis techniques, and a regioselective protonation at a nitrogen atom of 1 − was observed.