C–O bond hydrogenolysis of cyclic ethers with OH groups over rhenium-modified supported iridium catalysts

Hydrogenolysis of tetrahydrofurfuryl alcohol to 1,5-pentanediol and other related substrates such as 3-hydroxytetrahydrofuran and 1,2-cyclohexanediol proceeds over Ir–ReOx/SiO2 catalyst. TOF values are higher than those of Rh–ReOx/SiO2, which has been reported to be an effective catalyst. The selectivity to the product, where the C–O bond neighboring the C–OH group in the substrate is dissociated, is comparable to or higher than that of Rh–ReOx/SiO2. Hydrogenolysis of most substrates except 1,2-cyclohexanediol proceeds via the direct mechanism where hydride species formed from hydrogen molecule attacks the anti-position of C–O bond. In the case of hydrogenolysis of 1,2-cyclohexanediol where attack of anti-position of C–O bond is unfavorable, indirect mechanism involving dehydrogenation to 2-hydroxycyclohexanone is responsible for the formation of cyclohexanol.