InSitu Generated Zinc(II) Catalyst for Incorporation of CO2 into 2-Oxazolidinones with Propargylic Amines at Atmospheric Pressure

Incorporation of CO2 into heterocyclic compounds (i.e., 2-oxazolidinones) under mild conditions, especially at atmospheric pressure still remains challenging. The mononuclear Zn-II complex ZnCl2(TBD)(2), where TBD=1,5,7-triazabicyclo[4.4.0]dec-5-ene, in this study was demonstrated as a robust catalyst for the carboxylative cyclization of propargylic amines with CO2 to exclusively afford various 2-oxazolidinones in excellent yields. Notably, the Zn-II catalytic species is readily generated insitu from ZnCl2 and TBD without pre-preparation and further isolation. Such a CO2 fixation protocol could proceed smoothly under atmospheric pressure at mild temperature in an atom economic and environmentally benign manner. (CNMR)-C-13 and control experiments were performed to explore the possible interaction between Zn-II and the carbon-carbon triple bond of propargylic amine. The dual catalytic role of the Zn catalyst to enhance O-nucleophilicity of the carbamate anion intermediate and activate the carbon-carbon triple bond is proposed based on mechanistic investigations.