The general procedure for the synthesis of 5-bromo-2-fluoro-3-formylpyridine using N-formylpiperidine and 2-fluoro-5-bromopyridine as starting materials was as follows: the intermediate 5-bromo-1H-pyrazolo[3,4-b]pyridine was first prepared; subsequently, the crude product was ground in hexane (replacing the operation of crystallization from cyclohexane) according to the method described in WO2006015124 to obtain the target compound 5-bromo-2-fluoro-3-formylpyridine, the product was an off-white solid in 68% yield. Mass spectrometry (electrospray positive ion mode) showed m/z of 203.8 and 205.7 [M+H]+.
