Green synthesis of oxadiazolo[2,3-b]quinazolin-5-ones based on iodine-catalyzed cyclodesulfurization in water

Oxadiazolo[2,3-b]quinazolin-5-ones are a rare class of heterocycles exhibiting herbicidal and fungicidal activities. We found that the cyclodesulfurization of 2-thioxo-3(2H)-quinazolinyl)benzamides prepared from methyl 2-isothiocyanatobenzoates and benzoylhydrazines afforded oxadiazolo[2,3-b]quinazolin-5-ones by the mediation of catalytic iodine in moderate to excellent yields. The reactions proceeded smoothly in water with the presence of terminal oxidant and base under mild reaction conditions.