Computational studies on the mechanism of the copper-catalyzed sp ³-C-H Cross-Dehydrogenative coupling reaction

A detailed computational study of a copper-catalyzed aerobic cross-dehydrogenative coupling reaction has been conducted. To select a reliable method to describe the thermochemistry of a single electron transfer (SET) process, benchmark calculations have been performed. M06/6-311+g(d,p) is appropriate to evaluate the thermochemistry of the SET process for the system involving iminium species. The computational results support an SET mechanism, but also uncover an alternative mechanism in which O₂ is directly involved in a hydrogen-abstracting step. A comparative study with tert-butylhydroperoxide (TBHP) as the oxidant has also been performed. The computations reveal several competitive pathways, including a radical pathway, a Cu^III pathway, and an SET mechanism for the Cu/TBHP system.