The reaction of hydrazine with dibenzofuran-1, 2-dicarboxylic anhydrides followed by treatment with acetic acid resulted in the formation of 1, 4-dioxo-1, 2, 3, 4- tetrahydrobenzofuro [3, 2-f] phthalazines. Dibenzofuran-1, 2-dicarboxylic anhydrides were prepared by the Diels-Alder reaction of 2-alkenyl benzofurans and maleic anhydride followed by oxidative aromatization. Chlorination of 1, 4-dioxo-1, 2, 3, 4- ...