Green synthesis of coumarins via Pechmann condensation catalyzed by reusable functionalized organosilica

Abstract

Oxygen-containing heterocycles hold diverse uses in biology and organic chemistry. Herein, a method utilizing a functionalized pyridinium protic ionic liquid framework (PMO-Py-IL) was developed for the solvent-free Pechmann synthesis of coumarins from phenols and ethyl or methyl acetoacetate. High to excellent product yields were obtained under the investigated conditions. PMO-Py-IL remained stable and reactive across multiple reaction runs (up to 12 times), showcasing its stability and efficiency. The ionic nature of the catalyst can increase the polarity of the reaction mixture, leading to improved solubility of reactants and facilitating their interaction. This ultimately stabilizes the intermediates and accelerates the reaction, resulting in higher yields of the desired product. This can further speed up the reaction and increase the yield of the desired product. The proposed approach provides an efficient, simple and easy work-up methodology for coumarin synthesis, with outstanding nanocatalyst's reusability, offering environmental and economic advantages.