One-pot, three-component synthesis of 2,3-dihydroquinazolin-4(1H)-ones using p-toluenesulfonic acid-paraformaldehyde copolymer as an efficient and reusable catalyst

p-Toluenesulfonic acid-paraformaldehyde copolymer (copolymer-PTSA) catalyzes the three-component, one-pot condensation reaction of isatoic anhydride, ammonium salts or aromatic and aliphatic amines, and aldehydes in refluxing ethanol. The catalyst is reusable and could be recycled for several runs without any decrease in its efficiency.