The general procedure for the synthesis of 1,4-dioxo-1,2,3,4-tetrahydrophthalazine-6-carboxylic acid from trimellitic anhydride was as follows: hydrazine hydrate (26 g, 0.52 mol) was added in a single addition to a stirred solution of acetic acid (1.0 L) of trimellitic anhydride (100 g, 0.52 mol) at room temperature. Subsequently, the reaction mixture was heated to 120 °C and maintained for 2 hours. After completion of the reaction, the mixture was cooled to room temperature. The solid product was collected by filtration and washed with deionized water (250 ml). Finally, the product was dried in a vacuum oven at 50 °C for 20 h to afford 1,4-dioxo-1,2,3,4-tetrahydrophthalazine-6-carboxylic acid (91 g, 85% yield).
