Synthesis, characterization and derivatizations of quinazolin-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 environmentally benign H2O2-tungstate oxidant system at room temperature. High yielding one-pot procedure was also developed for the synthesis of compounds 3. The use of manganese triacetate as an oxidant component in the C-4 arylations of 2-aryl-quinazoline 3-oxides with arylboronic acids is reported. The new protocol was applied to prepare new 2,4-diarylated quinazoline 3-oxides in good to high yields. The method was shown to tolerate variety of substituents on both aromatic rings and no complications as deoxygenation and rearrangement to quinazolin-4(3H)-one were observed. Quinazoline-3-oxides 3 were shown to undergo hydrolytic ring opening in the presence of ZrOCl2 to give the corresponding N-(2-((hydroxyimino)methyl)phenyl)-benzamides 9. The latter can be recyclized in DMSO using catalytic amounts of an acid.