An efficient synthesis of 4-aryl-7-benzylidene-hexahydro-2H-cyclopenta[d] pyrimidin-2-ones/thiones catalyzed by p-dodecylbenzenesulfonic acid

A new and efficient method has been developed for the synthesis of 4-aryl-7-benzylidene-1,3,4,5,6,7-hexahydro-2H-cyclopenta[d]pyrimidin-2-ones through Biginelli-like reaction of cyclopentanone, with urea/thiourea and aromatic aldehyde employing p-dodecylbenzenesulfonic acid (DBSA) as a recyclable catalyst under solvent-free condition. The recovered catalyst was recycled for further runs. The product formation takes place via a cross-aldol condensation of benzaldehyde with cyclopentanone in the presence of DBSA to produce benzylidene intermediate and subsequent Michael addition. The present approach offers the advantages of short reaction time, mild reaction conditions, high yields and convenient operation. All the products were obtained in good to excellent yields and the structures of the synthesized compounds were established by advanced spectroscopic data.