Green Synthesis of Tetracyclic Quinazolinones Based on Iodine-Catalyzed Oxidative Desulfurative Cyclization in Water

Abstract

Green method for the synthesis of 12H-benzo[4,5]oxazolo[2,3-b]quinazolin-12-one derivatives, a rare class of tetracyclic heterocycles, has been realized. Reaction of methyl isothiocyanatobenzoates with 2-aminophenols formed 3-(2-Hydroxyphenyl)-2-thioxo-2,3-dihydroquinazolin-4(1H)-ones, which were treated in situ with a catalytic amount of iodine in the presence of oxidant and base to provide the desired 12H-benzo[4,5]oxazolo[2,3-b]quinazolin-12-ones in good yields in water as a green solvent. A range of functional groups has been tolerated through the transformations.