Efficient solid-phase synthesis of quinazoline-2,4-diones with various substituents on aromatic rings

We have developed a method for the solid-phase synthesis of quinazoline-2,4-diones with various substituents on the aromatic ring. Although there have been numerous reports of the solid-phase synthesis of quinazoline-2,4-diones, they were not applicable to the synthesis of the quinazoline-2,4-diones with electron-withdrawing substituents on the aromatic ring. Considering the poor nucleophilicity of the amino group of anthranilic acids, coupling of anthranilic acids to solid-supported amines was investigated without protecting the amino group. Various anthranilamides were prepared using anthranilic acids with electron-withdrawing substituents because a wide range of anthranilic acids are commercially available. These anthranilamides were successfully cyclized with carbonyldiimidazole to give quinazoline-2,4-diones with high purity.