Sulfonated Carbon Catalyzed Biginelli Reaction for One-Pot Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones and -thiones

A sulfonated carbon material was shown to be a highly efficient, eco-friendly, and recyclable solid acid catalyst for the Biginelli reaction of beta-ketoester, aldehyde, and urea or thiourea under solvent-free conditions. It gave 3,4-dihydropyrimidin-2(1H)-ones and -thiones in good to excellent yields. This method has the advantages of a simple procedure with easy work-up, short reaction time, and high yields. The catalyst can be recycled after a simple work-up and was reused four times without substantial reduction in activity.