Amine Mediated Photoreduction of Aryl Ketones in N-Heterocyclic Ionic Liquids: Novel Solvent Effects Leading to Altered Product Distribution

摘要

Amine mediated photoreduction of benzophenones in N-heterocyclic ionic liquids produces the corresponding benzhydrols as the major product instead of the expected benzpinacols. The ratio of benzhydrol to benzpinacol is a function of the reduction potential of the intermediate ketyl radical. Results consistent with a mechanism involving a dark electron transfer between the ketyl radical and a-amino radical are presented. Other important factors contributing to the observed benzhydrol/benzpinacol ratio are solvent viscosity and reduction potential of the cation.