Chemoselective 1,2-Reduction and Regiodivergent Deuteration of Chromium-Bound Arenes

Herein, a general strategy for chemo- and regioselective 1,2-reduction of chromium-bound arenes was developed, thus providing rapid access to 1,3-cyclohexadienes. Selective arene activation via π-complexation along with the use of mild hydride Ph₃ SiH can overcome the inherently low reactivity of arene π-bonds while tolerating various reduction-sensitive functional groups. Its versatility further enables a regiodivergent deuteration. Using different sequences of (non)deuterated hydride and acid reagents, the deuterated positions as well as the degrees of deuterium incorporation can be controlled precisely, which leads to a large and previously inaccessible chemical space for 1,3-cyclohexadiene isotopologues. A reasonable mechanism was proposed based on intermediate capture and control experiments. The synthetic value of this selective 1,2-reduction was demonstrated in the formal total synthesis of (±)-galanthamine and (±)-lycoramine.