Highly efficient reusable carboxy group functionalized imidazolium salts for the simple and cost-effective preparation of pyrano[2,3-d]pyrimidinone derivatives

Aim and Objective: In the current study, an environmentally benign and cost-effective procedures were suggested for the preparation of carboxy group functionalized imidazolium salts including [Cmmim]BF4- or [Cmmim]Br- as a new, re-usable Brønsted acidic ionic liquid (BAIL) catalyst. Then, the catalytic performance of [Cmmim]BF4- or [Cmmim]Br- were successfully inspected towards the three‐components one‐pot preparation of pyrano[2,3-d]pyrimidinone derivatives 4a-4q. The mentioned procedure shows short reaction times, easy work-up procedure, green conditions, high yields of the products, high potent of recovering and reusing capability. Current study is useful and adequate for the application and development of imidazolium salts on the basis of green chemistry principles. Materials and Methods: An aromatic aldehyde (1 mmol), barbituric acid (1 mmol), and malononitrile (1 mmol) were placed in a round‐bottomed flask containing ethanol (5 mL). BAILs A and B (0.1 mmol, 10 mol%) was added to the mixture. The suspension was magnetically stirred at room temperature for an appropriate time (Table 2). After completion of the reaction, which was monitored by TLC (n‐hexane:ethyl acetate = 3:1), the pure product was filtered off to separate the catalyst, washed with water and recrystallized from ethanol to afford the pure compound. After separation of the product, the catalyst was recovered by evaporation of water, washed with Et2O, dried under vacuum for 2 h and reused for the same reaction. Results: The mentioned procedure shows short reaction times, easy work-up procedure, green conditions, high yields of the products, high potent of recovering and reusing capability. Conclusion: In this study, we unveiled the synthesis of a new acetic acid functionalized ionic liquids [Cmmim]BF4- BAIL A or [Cmmim]Br- BAIL B and its application for the preparation of pyrano[2,3-d]pyrimidinone derivatives via a three compo-nent reaction among various aromatic aldehyde, barbituric acid, and malononitrile under mild and metal-free conditions. A wide range of pyrano[2,3-d]pyrimidinone derivatives bearing diverse functional groups were obtained in short reaction and excellent yields. Operational simplicity, recoverability and reusability of catalysts, cheap and chemically stabile reagents, high catalytic activity, easy work-up, eco-friendly procedure, make this method environmentally benign and cost-effective.