Efficient Catalytic Deoxygenation of Epoxides Using [Tris(3,5-dimethylpyrazolyl)hydridoborato]rhenium Oxides

In situ reduction of Tp′ReO₃ (Tp′ = tris(3,5-dimethylpyrazolyl)hydridoborate) using triphenylphosphine or triethyl phosphite allows generation of a reduced rhenium species that catalyzes efficient O atom transfer from epoxides to the stoichiometric phosphorus reductant at 75-105°C. The reaction is stereospecific and proceeds most rapidly with cis- vs trans-alkenes. The choice of ligand is shown to impart advantages to design of the catalytic cycle.