Atmospheric Pressure of CO₂ as Protecting Reagent and Reactant: Efficient Synthesis of Oxazolidin-2-ones with Carbamate Salts, Aldehydes and Alkynes

Carbon dioxide (CO₂) has been wildly employed as an environmentally benign C₁ resource for organic synthesis in the recent years. The capture of CO₂ with primary amines easily provides the corresponding carbamate salts. We described herein that carbamate salts are a useful reactant for the synthesis of oxazolidin-2-ones via the reaction with aromatic aldehydes and aromatic terminal alkynes. A variety of oxazolidin-2-ones with different functional groups were synthesized in 68-91% yields with only a 5 mol% amount of CuI as catalyst. It was found that the synergetic effect of iodide is important for the transformation. Notable, the captured CO₂ serves not only as a protecting reagent for electron-rich primary amine to avoid catalyst poisoning, but also as a reactant for the construction of oxazolidin-2-ones.