The condensation reaction of ethyl 4-oxo-4H-benzo[d][1,3]oxazine-2-carboxylates with acidic solution of potassium cyanate offers a novel and expedient route to the synthesis of 2,4(1H,3H)-quinazolinediones under mild reaction conditions.
Simple one-pot synthesis of ethyl 4-oxo-4H-benzo[d][1,3]oxazine-2-carboxylates is described by condensation reaction of anthranilic acid derivatives with ethyl 2-chloro-2-oxoacetate in CHCl3. High yields of the products obtain in high purity with simple work-up.