Facile synthesis of 3,4-dihydropyrimidin-2(1H)-ones and -thiones and indeno[1,2-d]pyrimidines catalyzed by p-dodecylbenzenesulfonic acid

A facile method for synthesizing 3,4-dihydropyrimidin-2(1H)-ones and -thiones in the Biginelli reaction by condensation reaction of aldehydes, β-ketoesters and urea or thiourea with p-dodecylbenzenesulfonic acid as a recyclable catalyst under solvent-free conditions at 80 °C is described. A series of indeno[1,2-d]pyrimidines was also synthesized under the same conditions by a Biginelli-like reaction of 2H-indene-1,3-dione with urea or thiourea and an aromatic aldehyde. All the products in both reactions were obtained in good to excellent yield by this simple, efficient procedure. The structures of all the synthesized compounds were established from advanced spectroscopic data.