The general procedure for the synthesis of 3,6-di-2-pyridyl-1,2,4,5-tetrazine from the compound (CAS: 19081-87-9) was as follows: 8.0 g (0.077 mol) of 2-cyanopyridine was dissolved in 200 mL of anhydrous ethanol and transferred to a three-neck flask. Subsequently, 9.54 mL (0.308 mol) of 95% hydrazine hydrate was added to the solution. The mixture was refluxed for 6 h. Upon completion of the reaction, 7.54 g (81.7% yield) of orange dianhydride-based product was obtained. The solid was collected by filtration, washed several times with ethanol and then dissolved in glacial acetic acid. Under cooling conditions in an ice bath, 5-6 mL of concentrated nitric acid was added slowly and dropwise. After the reaction was completed, the mixture was poured onto crushed ice and adjusted to alkaline with sodium bicarbonate, followed by two extractions with chloroform. The organic layers were combined, dried over anhydrous sodium sulfate and concentrated under reduced pressure to give 6.3 g (85% yield) of 3,6-bis(2'-pyridinyl)-1,2,4,5-tetrazine as a purple solid. 6.3 g (0.027 mol) of the resulting 3,6-bis(2'-pyridyl)-1,2,4,5-tetrazine was dissolved in dimethylformamide (DMF) and transferred to a three-neck flask. Acetylene gas was passed into the solution and refluxed. During the reaction, the color of the mixture gradually changed from purple to transparent. After completion of the reaction, DMF was evaporated under reduced pressure and the residue was extracted with ethyl acetate. The resulting solid was purified by silica gel column chromatography with the eluent ethyl acetate:hexane (1:4, v/v).
