Rhodium-catalyzed hydrogenation of olefins in -valerolactone-based ionic liquidsElectronic supplementary information (ESI) available. See DOI: 10.1039/c3gc40360b

-Valerolactone-based ionic liquids were successfully used as the catalyst phase for [Rh(cod) 2 ][BF 4 ]/RP(C 6 H 4 - m -SO 3 Na) 2 (R = Me, Pr, Bu, Cp) catalyzed hydrogenation of different olefins. Compared to broadly used ionic liquids e.g. 1-butyl-3-methylimidazolium chloride [bmim][Cl], the turnover frequencies were significantly higher and the reaction was selective for the C&z.dbd;C double bonds in the presence of carbonyl, cyano, and phenyl groups. The catalyst was recycled for ten consecutive runs under regular or biphasic conditions without loss of activity. The vapour pressure and viscosity of -valerolactone-based ionic liquids were determined as well. -Valerolactone-based ionic liquids were synthesized, characterized and used as the catalyst phase for selective rhodium-catalyzed hydrogenation of different olefins with excellent yield.