General procedure for the synthesis of 3-bromo-5-cyanoindazole from indazole-5-carbonitrile: 1H-indazole-5-carbonitrile (90 mg, 0.62 mmol) was dissolved in anhydrous N,N-dimethylformamide (DMF, 1 mL), and N-bromosuccinimide (NBS, 134 mg, 0.75 mmol) was added slowly at room temperature. The reaction mixture was stirred continuously for 2 hours at room temperature. Upon completion of the reaction, the solvent DMF was removed by distillation under reduced pressure. the residue was dissolved in ethyl acetate and washed with saturated aqueous sodium bicarbonate, deionized water and saturated saline in that order. The organic phase was dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give 3-bromo-5-cyanoindazole (128 mg, 93% yield). Low resolution mass spectrometry (LRMS) showed m/z: 222/224 (Br isotope peak).
