Carbon monoxide gas and ligand-free conditions were developed for the synthesis of 2-hydroxy-3-alkyl-2-phenyl-2,3-dihydroquinazolin-4(1H)-one via catalytic carbonylation with molybdenum hexacarbonyl as an efficient carbonylating agent for the three-component reaction of isatoic anhydride, amine, iodobenzene. Mo(CO)₆ is a solid carbon monoxide source. The quinazolinone synthesis proceeds via a sequential series of reactions such as nucleophilic attack of the amine group on the carbonyl group of isatoic anhydride followed by ring opening, subsequent decarboxylation, carbonylation and heterocyclization.