Chemoselective reduction of heteroarenes with a reduced graphene oxide supported rhodium nanoparticle catalyst

Rhodium nanoparticles immobilized on reduced graphene oxide were obtained from the microwave-induced thermal decomposition of Rh-6(CO)(16) in the ionic liquid [bmim][BF4] (bmim = 1-butyl-3-methylimidazolium cation) in the absence of additional stabilizing agents. The resulting rhodium nanoparticles are <4 nm in diameter and are evenly dispersed on the reduced graphene oxide. The composite was evaluated as a catalyst for the chemoselective hydrogenation of quinoline and other heteroarenes containing N- and O-heteroatoms. A high selectivity for the heterocyclic ring was achieved, typically >99%, without interfering with other reducible groups, and with high conversions. Related catalysts prepared using conventional thermal heating were prepared for comparison purposes and were found to be considerably less active.