An Aminopyridinium Ionic Liquid: A Simple and Effective Bifunctional Organocatalyst for Carbonate Synthesis from Carbon Dioxide and Epoxides

Abstract

Abstract An aminopyridinium ionic liquid is presented as a green, tunable, and active metal‐free one‐component catalytic system for the atom‐efficient transformation of oxiranes and CO 2 to cyclic carbonates. Inclusion of a positively charged moiety into aminopyridines, through a simple single‐step synthesis, provides a one‐component ionic liquid catalytic system with superior activity; effective in ring opening of epoxide, CO 2 inclusion, and stabilization of oxoanionic intermediates. An efficiency assessment of a variety of positively charged aminopyridines was pursued, and the impact of temperature, catalyst loading, and the kind of nucleophile on the catalytic performance was also investigated. Under solvent‐free conditions, this bifunctional organocatalytic system was used for the preparation of 18 examples of cyclic carbonates from a broad range of alkyl‐ and aryl‐substituted oxiranes and CO 2 , where up to 98 % yield and high selectivity were achieved. DFT calculations validated a mechanism in which nucleophilic ring‐opening and CO 2 inclusion occur simultaneously towards cyclic carbonate formation.