Iron(III) tosylate catalyzed synthesis of 3,4-dihydropyrimidin-2(1H)-ones/thiones via the Biginelli reaction

The synthesis of dihydropyrimidinones and dihydropyrimidine thiones has attracted interest due to their biological activities. A common method for their synthesis is the Biginelli reaction, which is a one-pot condensation of an aryl aldehyde, urea (or thiourea), and ethyl acetoacetate. The Biginelli reaction is typically catalyzed by a Brّnsted or Lewis acid. However, many of these catalysts such as BF3·Et2O and AlCl3 are corrosive and/or toxic. Our continued interest in environmentally friendly organic synthesis prompted us to investigate the utility of iron(III) tosylate as a catalyst for the Biginelli reaction. The use of acetals in the Biginelli reaction is also reported. Iron(III) tosylate is an attractive catalyst for the Biginelli reaction because of its low cost, low toxicity, and ease of handling.