Mechanistic study of the titanocene(III)-catalyzed radical arylation of epoxides.

An atom-economical and catalytic arylation of epoxide-derived radicals is described. The key step of the catalytic system is a sequential electron and proton transfer for the rearomatization of the radical σ-complex and catalyst regeneration. Kinetic, computational, spectroscopic, and cyclovoltammetric investigations highlight the key issues of the reaction mechanism and catalyst stabilization by collidine hydrochloride.

Radical-based epoxide opening by titanocenes.

The binding of 2,2-diphenyloxirane to Cp2TiCl is studied on the electronic level by magnetic resonance spectroscopy and quantum chemical calculations. The complexation of 2,2-diphenyloxirane is accompanied by dissociation of the chloride ligand, and thus, the epoxide binds to the cationic titanocene(III) complex. The titanocene(III)-epoxide species persists only for short periods of time (<5 min) even at 243 K, indicating that the ring-opening reaction is exothermic.