Synthesis of 4-phenyloxazinones via DBU-catalyzed cleavage of 4-bromomethylcoumarins

A new route for ring transformation has been discovered during the reaction of 4-bromomethylcoumarins with hydroxyl amine in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), leading to the formation of pharmacologically important 1,2-oxazinones in a single step with very high yields.