One-Pot Synthesis of <i>N</i>-Substituted Carbamic Acid Esters from Low Concentrations of CO₂

Abstract

Organic syntheses, such as that of N-substituted carbamic acid esters (CAEs), utilizing low purity and low concentrations of CO2 directly, may help achieve two important goals─reducing CO2 emission and producing useful core chemicals without the energy-consuming processes of purifying and concentrating CO2. Here, we demonstrate a new synthetic approach for CAEs that uses a combination of two types of CO2 capture mechanisms, which are constituted by combining an amine and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and an alcohol and DBU, to form a protonated DBU carbamate salt and a protonated DBU alkyl carbonate salt, respectively. This new approach of CAE synthesis can be applied even to the simulated exhaust gas from fire-power plants, such as 3 vol % of CO2 in N2 or 15 vol % of CO2 in N2, also containing SO2, NO2, and CO.