Synthesis
General procedure for the synthesis of 4-bromopyridine-2-carboxaldehyde from 2-hydroxymethyl-4-bromopyridine: 3L of dichloromethane (DCM) was added to a 5L three-necked flask under nitrogen protection, and cooled to -60 °C. During the cooling process, 240 g of oxalyl chloride was added slowly and dropwise. Maintaining the reaction temperature at -60 °C, 295.6 g of dimethyl sulfoxide (DMSO) was added dropwise to the reaction system and held for 30 min after the dropwise addition. Subsequently, 237.5 g of 2-hydroxymethyl-4-bromopyridine (Cpd 3) was slowly added dropwise at -60 °C and the reaction was continued at -65 °C for 1 hour. At this temperature, 3.5 equivalents of triethylamine (TEA) was added, and the reaction solution was allowed to stand before the progress of the reaction was monitored by thin layer chromatography (TLC). Upon completion of the reaction, the target product 4-bromopyridine-2-carboxaldehyde (Compound 4) was purified by column chromatography to give 177.2 g in 75% yield.
References
[1] Patent: US2010/125082, 2010, A1. Location in patent: Page/Page column 24
[2] Tetrahedron, 1997, vol. 53, # 24, p. 8257 - 8268
[3] Patent: CN108516953, 2018, A. Location in patent: Paragraph 0067-0068; 0074-0075; 0076-0083
[4] Chemical and Pharmaceutical Bulletin, 1990, vol. 38, # 9, p. 2446 - 2458
[5] MedChemComm, 2015, vol. 6, # 7, p. 1252 - 1259
