Diammonium hydrogen phosphate: A versatile and inexpensive reagent for one-pot synthesis of dihydropyrimidinones, quinazolinones and azalactones under solvent-free conditions

Diammonium hydrogen phosphate, (NH4)(2)HPO4, efficiently catalyzes the three-component Biginelli reaction between an aldehyde, a beta-dicarbonyl compound and urea or thiourea under solvent-free conditions to afford the corresponding dihydropyrimidinones in high yields. Also, the synthesis of 2,3-disubsitituted-(3H)-quinazolin-4-ones is achieved by the one-pot reaction of isatoic anhydride, primary amines and orthoesters in the presence of (NH4)(2)HPO4. The reaction of hippuric acid with aromatic aldehydes and acetic anhydride resulted in the formation of azalactones using catalytic amounts of (NH4)(2)HPO4.