Alkali Metal Salt as Catalyst for Direct Synthesis of Carbamate from Carbon Dioxide

Abstract

Carbamates are an important motif in agricultural chemistry, medicinal chemistry, and polyurethane preparation. Potassium carbonate (K2CO3) is a common, nontoxic, and inexpensive chemical and is widely used in organic synthesis. Herein we report the use of K2CO3 as a catalyst for direct synthesis of carbamate from amine, silicate ester, and carbon dioxide. Especially, both alkyl amines and aromatic amines could be activated, largely expanding the substrate scope compared with the use of alcohol as the coupling reagent. Anion-assisted deprotonation of amine was the key step in the catalytic process, and the alkali metal served as a Lewis acid. Isolated yield of the corresponding carbamate was up to 97%. The use of K2CO3 as the catalyst decreased 49 kJ mol–1 activation energy of the reaction compared with our previously reported ionic liquid catalyst from Arrhenius analyses.