Ruthenium-Catalyzed Selective Hydrogenation of Benzene to Cyclohexene in the Presence of an Ionic Liquid

Reducing circumstances: The hydrogenation of benzene in organic phase leads rapidly to cyclohexane. A very simple catalyst system comprising only supported ruthenium in water with the addition of the ionic liquid 1 (R=Me) in the ppm range catalyzes the extremely difficult selective hydrogenation of benzene to cyclohexene. It is not necessary to add large amounts of salt (ZnSO4) or other metals, which is otherwise done to control selectivity.