DBU and DBU-Derived Ionic Liquid Synergistic Catalysts for the Conversion of Carbon Dioxide/Carbon Disulfide to 3-Aryl-2-oxazolidinones/[1,3]Dithiolan-2-ylidenephenyl- Amine

An intermolecular synergistic catalytic combination of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and a DBU-derived bromide ionic liquid has been developed for the conversion of CO₂, epoxides, and amines under metal- And solvent-free conditions. Various 3-aryl-2-oxazolidinones are produced in moderate to excellent yields within a short reaction time. NMR spectroscopy and DFT calculations demonstrate that DBU as a hydrogen bond acceptor and the ionic liquid as a hydrogen bond donor activate the substrates cooperatively by inducing hydrogen bonds to promote the reaction effectively. Based on these results, a possible reaction mechanism on the synergistic catalysis of DBU and the ionic liquid is proposed. In addition, the reaction of CS₂, ethylene oxide, and aniline catalyzed by the combination of DBU and the DBU-derived ionic liquid also proceeds smoothly, which opens a hitherto unreported route to [1,3]dithiolan-2-ylidenephenylamine in a straightforward way.