O-Carboxymaleanilic acids IIIa-g when treated with sodium acetate-acetic anhydride underwent double cyclisation leading to pyrrolobenzoxazinones Va-g carrying an angular acetate. A one-flask reaction of dimethylmaleic anhydride and phthalic anhydride with anthranilic acid furnished the angular hydroxy benzoxazinones IVh and IVi respectively, which were converted to the corresponding acetates Vh and Vi. The acetates Va, Vc, Vf, ...
