One-pot reductive cyclization to antitumor quinazoline precursors

A highly efficient and versatile synthetic approach to the central core of anti-cancer quinazolinone derivatives is reported. Intermolecular reductive N-heterocyclizations of various 2-nitrobenzoic acid derivatives with formamide were catalyzed by indium(III) or bismuth(III) salts to yield the title compounds in high yields and excellent purities. In the present one-pot sequence, the arylnitro group is apparently reduced by formamide decomposition product carbon monoxide and the resultant anthranilic acid derivative proceeds to Niementowski cyclocondensation to form quinazolinones. The transformation is robust for diverse substituents on the aryl group and In(III) counterions, and is also compatible with N-alkyl formamides but not dimethylformamide.