Microwave-assisted Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones Using Acid-Functionalized Mesoporous Polymer

Abstract

Background: In recent years, 3,4-dihydro-pyrimidin-2-(1H)-ones (DHPMs) have attracted significant attention due to their diverse range of biological properties such as antibacterial, antiviral, antitumor, anti-inflammatory, calcium channel blocking activities, etc. Taking into account, in this present work, a polymer-based solid acid catalyst is employed for the microwaveassisted synthesis of DHPMs. Introduction: Multicomponent reactions (MCRs) are attracting utmost attention as they promote the formation of several bonds in a single process with diverse advantages. Biginelli reaction is the top-ranked example of MCR for the synthesis of dihydropyrimidinones (DHPMs). Solid catalysts are considered a significant tool for MCRs as they are non-toxic, easy to handle, reusable, and have high selectivity and easy separation process. Methods: DHPMs synthesis was carried out using acid-functionalized mesoporous polymer (AFMP) catalyst under microwave irradiation and solvent-free condition. Results: AFMP showed good to excellent DHPMs yield (89-98%) under the optimized reaction conditions: 1:1:1.2 molar ratio of aldehyde/ethyl acetoacetate/urea, catalyst loading of 6 wt.% (with respect to aldehyde), the temperature of 80 °C and microwave power of 500 W. Conclusion: We have successfully utilized microwave-assisted AFMP catalyst for the synthesis of DHPMs under solvent-free conditions via the Biginelli approach. The catalyst is recyclable and reusable in up to 5 consecutive reaction cycles with no significant loss in catalytic activity.