ON MECHANISM OF PHOTOREDUCTION OF ARYL N-ALKYLIMINES

The mechanism and scope of the photoreduction of some aryl N-alkylimines is described. Irradiation of a series of benzaldehyde N-alkylimines in 95% ethanol affords dihydro photodimers, whereas irradiation of several benzophenone N-alkylimines gives the reduced benzhydrylalkylamines. The excited states of the imines were shown not to be reactive intermediates but instead ketyl radicals were clearly implicated as the active reducing agent. These ketyl radicals were derived from carbonyl compounds present in the reaction mixture as an impurity, an added sensitizer, or as a photogenerated species. Comment is made regarding the relevance of these results to previous reports of imine photoreduction and photoalkylation. © 1969, American Chemical Society. All rights reserved.