Ionic liquids as solvents for a ruthenium-catalyzed C–H activation reaction: synthesis of heterocyclic compounds from α,β-unsaturated imines, carbon monoxide, and ethylene

Abstract

The reaction of α,β-unsaturated imines, carbon monoxide, and ethylene in the presence of Ru3(CO)12 as a precatalyst yielding mixtures of chiral 2,3-dihydropyrrolones and 2,3-disubstituted pyrroles has been performed in several ionic liquids as reaction media. Optimization of the reaction conditions in [C4mim][BTA] showed that the reaction works under milder conditions with regard to reaction time and partial pressures of the gaseous substrates than when performed in classical organic solvents. In some cases the ionic liquid phase containing the ruthenium catalyst species might even be reused for another run after extracting the products. A decrease of catalytic activity or changes in selectivity are attributed to the formation of ruthenium nanoparticles during the reaction.