Synthesis
Oxalyl chloride (13.2 mL, 150 mmol) was dissolved in anhydrous dichloromethane (86 mL) under nitrogen protection and cooled to -78°C. Dimethyl sulfoxide (21.2 mL) was added slowly dropwise over 20 min and the reaction mixture was stirred at -78°C for 15 min. Subsequently, 4-cyanopyridine-2-methanol (4.0 g, 30 mmol) dissolved in anhydrous dichloromethane (60 mL) was added dropwise to the reaction mixture over a period of 5 min and stirring was continued for 2 h while maintaining -78°C and a nitrogen atmosphere. Formation of a white solid precipitate was observed during the reaction. The reaction temperature was raised to -55°C and triethylamine (6.15 mL, 450 mmol) was added dropwise over 15 minutes. The cooling bath was removed and the reaction mixture was allowed to warm naturally to room temperature over a period of 2 hours. Upon completion of the reaction, the mixture was diluted with dichloromethane (400 mL), washed successively with brine (2 x 50 mL), and the aqueous phase was then back-extracted with dichloromethane (3 x 50 mL). All organic layers were combined and concentrated under reduced pressure to give a light yellow solid product. The product did not require further purification and showed a single peak by LC-MS analysis with a retention time (RT) of 2.53 min and a mass spectrometry (M + H) peak located at m/z 133.0 in quantitative yield.
References
[1] Patent: WO2006/21801, 2006, A1. Location in patent: Page/Page column 65-66
[2] Chemical and Pharmaceutical Bulletin, 1990, vol. 38, # 9, p. 2446 - 2458
[3] Patent: US6043248, 2000, A
[4] Patent: WO2006/21801, 2006, A1. Location in patent: Page/Page column 46-47
[5] Bioorganic and Medicinal Chemistry, 2014, vol. 22, # 1, p. 559 - 576
