The coupling of CO2 with diols promoted by organic dual systems: Towards products divergence via benchmarking of the performance metrics

Abstract

Herein, we propose a critical study balancing two metal-free dual activating systems, namely DBU/EtBr and TEA/TsCl, for the coupling of CO2 with 1,x-diols to afford (a)cyclic carbonates. In-situ ATR-IR monitoring correlated with DFT calculations led to mechanism propositions for the model formation of propylene carbonate from propylene glycol. Kinetics upon various experimental conditions were established for the first time, leading to an optimized synthetic protocol. The substrates scope was then investigated and selectivities toward the formation of cyclic or linear carbonates were correlated to the dual activating system and the diol structure. By choosing the suitable organic dual activating system, one is able to control the product selectivity to substituted ethylene- or trimethylene carbonate and/or acyclic compounds, providing a powerful tool to synthesize CO2-based precursors that are highly relevant for organic and polymer chemistry from ubiquitous building blocks.