Eco-friendly H2O2 oxidation of 1,2-dihydroquinazoline-3-oxides to quinazoline-3-oxides

2-Aminobenzaldehyde, 1-(2-aminophenyl)ethanone, and 2-aminophenyl phenyl methanone oximes 1 were reacted with aromatic aldehydes to give the corresponding 1,2-dihydroquinazoline-3-oxides 2. The latter were converted in high yields to a series of quinazoline-3-oxides 3 using an environmentally benign H2O2-tungstate oxidant system at room temperature. A high yielding one-pot procedure was also developed for the synthesis of compounds 3.