Guanidinium iodide salts as single component catalysts for CO2 to epoxide fixation

Abstract

In this study, we present the synthesis, characterization and catalytic reactions of a new family of one-component catalysts based on guanidinium salts. The synthesis of cyclic carbonates from epoxides and CO₂ at 70–80 °C under 1–5 bar of CO₂ pressure is demonstrated using the new one-component guanidinium salts with various substituents. The 1e catalytic system, which has isopropyl-type substituents in its structure, has the best conversion rates; the TON for the synthesis of styrene carbonate was 92. The production of cyclic carbonates from the internal epoxides is another application for these catalytic systems with the conversion of cyclohexane oxide to the respective cyclic carbonate at 86% with 1e catalyst. Finally, ESI-MS was used to examine the interaction of the new organocatalysts with CO₂ and epichlorohydrin. These findings led to catalysts made of organic molecules that are suitable for organocatalysis since they do not require a co-catalyst and can operate effectively at moderate pressures and temperatures.