Tandem catalysis: one-pot synthesis of cyclic organic carbonates from olefins and carbon dioxide

One-pot tandem procedures represent a green and general approach towards process intensification as they are intrinsically simpler compared to the conventional stepwise processes, do not require (potentially toxic) intermediate isolation or workup, and are generally more efficient in terms of use of materials. The current limit to the widespread diffusion of this kind of intensified approach lies in the need to design catalysts, reagents and/or solvents that can coexists during the whole course of the reaction, as well as in the development of systems that are sufficiently broad in terms of reagent scope. This tutorial review exemplifies a process intensification approach by describing the state-of-the-art and outlook for the direct one-pot two-step conversion of olefins into the corresponding cyclic organic carbonates without having to isolate intermediates (epoxides or bromohydrins) and by using carbon dioxide as a carbonate source. This conversion is crucial in green organic synthesis as it represents one way to efficiently incorporate CO2 into marketable molecules, starting from (potentially bio-based) unsaturated substrates. Currently, the stage has been set in the literature by demonstrating that model terminal olefins can be converted directly into their corresponding organic carbonates thanks to the development of new bi-functional catalytic systems and appropriate experimental conditions. In this specific field there is still however a wide margin for improvement in terms of substrates and higher efficiency.