Solvent-free synthesis of functionalized pyridine derivatives using Wells-Dawson heteropolyacid as catalyst

摘要

Wells-Dawson heteropolyacids (H6P2W_(18)O_(62)·24H2O) were used as catalysts in the Hantzsch-Iike multi-component condensation reaction with 3-formylchromones as aldehyde component, a p-ketoester and ammonium acetate, under solvent-free conditions at 80 °C. Although the desired products were obtained, functionalized pyridines were the main reaction product and became the alternative route to dihydropyr-idine ring formation. Based on the proposed mechanisms for the formation of each of the obtained products, the multicomponent reaction was modified to afford only the functionalized pyridines (60-99%). Our procedure represents a clean alternative for the synthesis of several highly functionalized pyridines.