Highly effective synthesis of 3, 4-dihydropyrimidin-2 (1H)-ones using pyridinium-N-sulfonic acid bisulfate as a dual-functional catalyst

Acidic ionic liquid pyridinium-N-sulfonic acid bisulfate ([Py-SO3H][HSO4]) has effectively catalyzed the production of 3, 4-dihydropyrimidin-2 (1H)-ones via the condensation reaction of the arylaldehydes with β-ketoesters and urea under solvent-free conditions. Due to the dual-functionality of [Py-SO3H][HSO4] (bearing acidic and basic sites), it was highly effective and general catalyst for the reaction. Additionally, an attractive mechanism for the dual-functionality of the catalyst was proposed.