The general procedure for the synthesis of 8-chloro[1,2,4]triazolo[1,5-a]pyrazine from the compound (CAS:74803-25-1) was as follows: the raw material (120 mg, 0.9 mmol) was mixed with phosphorus triclosan (5 mL), heated to 120 °C, and the reaction was carried out for 6 hours. Upon completion of the reaction, excess phosphorous trichloride was removed by vacuum concentration. The residue was diluted with ethyl acetate and washed with saturated aqueous sodium bicarbonate. The organic layer was dried over anhydrous sodium sulfate, filtered and concentrated in vacuum to afford the target compound 8-chloro[1,2,4]triazolo[1,5-a]pyrazine as a brown solid (50 mg, 36% yield), which could be used in the next reaction without further purification. Mass spectrum (electrospray ionization) m/z: 155.0 ([M+H]+).