Bifunctional homogeneous and recyclable heterogeneous single-component catalysts for the cycloaddition of CO₂ to epoxides were obtained through a simple method based on the ring-opening of opportunely functionalized epoxides and applied for the synthesis of cyclic carbonates under atmospheric CO₂ pressure.

Abstract

The design of molecular scaffolds bearing multiple functional groups for the activation and ring-opening of epoxides is a crucial challenge for the synthesis of efficient homogeneous and heterogeneous catalysts that are used for the cycloaddition reaction of CO₂ to epoxides. Traditional approaches to prepare such multifunctional catalysts often imply multistep synthetic procedures and expensive building blocks. In this work we show that bifunctional catalysts for the cycloaddition of CO₂ to epoxides bearing a Lewis acid metal and a quaternary ammonium halide group can be prepared in just two steps starting from an opportunely designed epoxide precursor by using inexpensive substrates. Such a readily accessible catalyst was applied for the cycloaddition of CO₂ to a series of epoxides under atmospheric conditions generally leading to quantitative substrate conversion and high carbonate selectivities. Importantly, we also show that the epoxide-driven concept developed for the preparation of the molecular catalyst, could be applied to prepare recyclable heterogeneous systems for the target cycloaddition reaction.