A temperature - controlled reversible ionic liquid - water two phase - single phase protocol for hydrogenation catalysis

摘要

An ionic liquid-water system that undergoes a reversible two phase - single phase transformation dependent upon temperature has been used as a novel medium for the transition-metal-catalyzed hydrogenation of a water soluble substrate. At room temperature, the ionc acid liqud 1-octyl-3-methylimidizolium tetrafluoroborate, containing [Rh(#eta#~4-C_7H_8)(PPh_3)_2][BF_4] catalyst, forms a separate layer to water containing 2-butyne-1,4-diol. In a stirred autoclave the mixture was pressurized with hydrogen to 60 atm (1 atm = 101.325 kPa) and heated to 80 deg C giving a homogeneous single phase solution. On cooling to room temperature, two phases reform, with the ionic liquid phase containing the catalyst and the aqueous phase containing a mixture of 2-butene-1,4-diol and butane-1,4-diol products that can be simply removed without catalyst contamination.