Tuning selectivity in terpene chemistry: selective hydrogenation versus cascade reactions over copper catalysts

The selectivity of Cu/Al2O3 under very mild catalytic hydrogenation conditions can be tuned only by switching the solvent. Geraniol can be converted in a one-pot one-step process into a mixture of citronellol and menthol in hydrocarbon solvents or reduced to citronellol with 98% selectivity in 2-propanol without any additive. Both reactions can be applied to essential oils or synthetic mixtures containing geraniol, citronellal and nerol.