The general procedure for the synthesis of 6-(hydroxymethyl)pyridine carboxaldehyde from 6-(hydroxymethyl)pyridine is as follows:P3: The alternative synthetic method is detailed in references [35-37]. The reaction was carried out under nitrogen protection. Hydroxylamine hydrochloride (600 mg, 8.63 mmol; excess) and 6-(hydroxymethyl)pyridine carboxaldehyde (750 mg, 5.47 mmol) were dissolved in DMSO (3 mL; 99.7% purity, degassed, additional drying treatment, sieved, moisture content <50 ppm, purchased from Acros), and reacted with stirring for 2 h at 100 °C (oil-bath temperature), the reaction solution was The reaction solution was dark red in color. After completion of the reaction, extraction was carried out with dichloromethane and saturated sodium bicarbonate solution. The aqueous phase was washed with saturated sodium chloride solution. The organic phase is re-extracted with saturated sodium bicarbonate solution to remove residual DMSO. the aqueous phase is back-extracted with dichloromethane in order to completely remove DMSO (due to its solubility in water) without loss of product. The organic phases were combined, concentrated by evaporation and purified by silica gel column chromatography (20 g), eluting first with dichloromethane to remove impurities and then with dichloromethane solution containing 0.5% methanol to give the target product. The product was a pale yellow solid with a yield of 446 mg (3.32 mmol; 61% yield; molecular formula C7H6N2O; molecular weight 134.14.
