The general procedure for the synthesis of 3,4-pyridinedicarboxylic acid as a raw material for the synthesis of 3,4-pyridinedicarboximides was as follows: firstly, sublimated 3,4-pyridinedicarboxylic acid (50 g, 300 mmol) was suspended in acetic anhydride (123.5 g, 1,200 mmol), and heated to reflux (140-150 °C) until the solid was completely dissolved and the mixture presented homogeneous state. Subsequently, the reaction mixture was cooled and concentrated under vacuum. Next, acetamide (50 g, 846 mmol) was added to the concentrate and the mixture was heated and reacted at 140 °C for 3 hours. After completion of the reaction, the mixture was cooled to room temperature. The solid residue formed during cooling was pulverized, ground with 100 ml of water, filtered and washed with additional water. Finally, the resulting solid was dried in a desiccator to afford 3,4-pyridinedicarboximide (42.26 g, 95.1% yield), which met the purity requirements for use without further purification. The product was analyzed by LC-MS showing a m/z (ESP) of 149 [M + H]+ and a retention time (R/T) of 0.44 min.
