Convenient synthesis of 2,3-disubstituted quinazolin-4(3H)-ones and 2-styryl-3-substituted quinazolin-4(3H)-ones: applications towards the synthesis of drugs

Simple, convenient, and green synthetic protocols have been developed for the one pot synthesis of 2,3-disubstituted quinazolin-4(3H)-ones and 2-styryl-3-substituted quinazolin-4(3H)-ones under catalyst and solvent free conditions. The multicomponent reaction (3-MCR) involving isatoic anhydride, an amine, and orthoester afforded the 2,3-disubstituted quinazolin-4(3H)-ones in excellent yields under classical heating at 120 degrees C for 5 h or under microwave irradiation at 140 degrees C for 20-30 min. The use of ammonium acetate instead of the amine provides the 2-substituted quinazolin-4(3H)-ones. The reactions are compatible with various substituted isatoic anhydrides, aryl/heteroaryl/alkyl/cycloalkyl amines, and orthoesters. The strategies are extended to the one pot tandem condensation involving isatoic anhydride, an amine, orthoester, and aldehyde to afford highly functionalized (E)-3-aryl/heteroaryl-2-styrylquinazolin/(2-(heteroaryl) vinyl) quinazolin-4(3H)-ones. The applications of the methodologies are demonstrated through the synthesis of various drugs which act on the central nervous system such as methaqualone, mebroqualone, mecloqualone, piriquialone, and diproqualone.