Contrasting Behavior of 1,3-Dimethyl-2-phenylbenzimidazoline (DMPBI) and 2-Hydroxyphenyl-1,3-dimethylbenzimidazoline (HPDMBI) in Photoinduced Electron Transfer Reactions with Benzophenones

Abstract

We have found that both benzhydrol and benzpinacol were obtained as major products in the photoreaction of benzophenone and 1,3-dimethyl-2-phenylbenzimidazoline (DMPBI), and their yields markedly varied depending on the kind of proton donor. On the other hand, in the photoreaction of benzophenone and 2-hydroxyphenyl-1,3-dimethylbenzimidazoline (HPDMBI), benzpinacol was a major product regardless of the reaction conditions. In order to investigate further photoinduced electron transfer reaction mechanism of DMPBI or HPDMBI with benzophenones, we conducted photoreaction of 3-methylbenzophenone as a probe substrate under the various reaction conditions. We also explored the properties of the oxidation products derived from DMPBI and HPDMBI.