Synthesis of carbonates from CO2 and epoxides catalyzed by the system of N‐heterocyclic carbene, hydrogen bond donor, CrCl2, and tetrabutylammonium bromide

Abstract

AbstractA three‐component catalytic system including pyridine‐bridged benzimidazolium salts, CrCl2, and tetrabutylammonium bromide (TBAB) was developed. Based on the control experiments and spectroscopic measurements, the role of the three components in the catalytic process was clarified, in which benzimidazolium salts were used as N‐heterocyclic carbene precursor, a new Cr complex generating from the coordination of CrCl2 with pyridine nitrogen and pyrazole nitrogen bearing benzimidazolium salts was employed as hydrogen bond donor, TBAB was used as nucleophilic reagent, respectively. Under mild conditions (50°C and 1 bar CO2), the terminal epoxides displayed high reactivity in the three‐component catalytic system. The catalytic system showed also high catalytic activity for the internal epoxides by increasing the temperature and CO2 pressure and/or prolonging the reaction time.