Hydrochloric Acid → 2-Chloro-3-pyridinecarboxaldehyde

200 ml of a 1.02M hexane solution of diisobutylaluminum hydride were added to a solution of 16.7 g of 2-chloro-3-cyanopyridine in 200 ml of tetrahydrofuran at a temperature of -30° to 20° C. over a period of 30 minutes, after which the resulting mixture was stirred at room temperature for 1 hour. At the end of this time, hydrochloric acid was added to the reaction mixture at 0° C, and then the mixture was extracted with ethyl acetate. The extract was washed with a saturated aqueous solution of sodium carbonate and with a saturated aqueous solution of sodium chloride, in that order, and then dried over anhydrous sodium sulfate, after which the solvent was removed by distillation under reduced pressure. The residue was purified by column chromatography through silica gel, using a gradient elution method, with mixtures of hexane and ethyl acetate in ratios ranging from 6:1 to 5:1 by volume as the eluent, to give 7.0 g of the title compound having Rf=0.50 (on silica gel thin layer chromatography using a 2:1 by volume mixture of hexane and ethyl acetate as the developing solvent).