General procedure for the synthesis of 3,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)-1,2-dihydro-1,2,4,5-tetrazine from 3,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)-1,2,4,5-tetrazine: 26.2 g of sodium nitrite was dissolved in 588 mL of water, 60 mL of dichloromethane was added, and the mixed solution was cooled to 0 °C. Subsequently, 37 g (0.136 mol) of 3,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)-1,2-dihydro-1,2,4,5-tetrazine was added to the solution and 18.67 mL (0.326 mol) of acetic acid was added slowly and dropwise. After the gas escape ceased, extraction was carried out with dichloromethane and the organic phase was washed with potassium carbonate solution. After drying over magnesium sulfate, the organic solvent was removed by rotary evaporation and finally recrystallized with ether to afford the target product 3,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)-1,2,4,5-tetrazine (33.45 g, 91% yield).
