Base-Mediated Direct Carboxylation of Heteroarenes with CO2

Abstract

AbstractA base medium system, generated from a synergistic reaction between Cs2CO3 and t-BuOK, has been used for the direct carboxylation of imidazoles with CO2 in good yield. Oxygen- and thia-heterocyclic arenes also undergo the carboxylation with CO2 with the same reactivity. Density functional theory calculations show that construction of t-BuOCs in situ is an endothermic process of 38.31 kJ/mol. t-BuOCs can promote the deprotonation of substrates by forming an active C–Cs bond via a rather low HOMO (t-BuOCs)–LUMO (imidazole) gap of 0.28 eV, which favors the electrophilic insertion of CO2 by releasing 94.13 kJ/mol of heat.