Synthesis of Tofisopam by Way of Photoinduced CO 2 Fixation

Herein reported is a unique synthetic route of Tofisopam, an anxiolytic drug containing a 2,3‐benzodiazepine core structure. 3,4‐Dimethoxypropylbenzene and 3,4‐dimethoxybenzoic acid, which are both of plant origin, and CO 2 constitute its carbon skeleton. These three renewable substances are united by two C−C bond forming reactions, i.e., a Friedel–Crafts acylation reaction and a photoinduced carboxylation reaction to construct the major carbon framework. Finally, a methyl group is introduced by a Kumada‐type cross‐coupling reaction to furnish Tofisopam. Various analogs of Tofisopam are readily synthesized by introducing other substituents than a methyl group at the last C−C bond forming step.