The general procedure for the synthesis of 2,6-dichloro-3-pyridinecarboxaldehyde from 2,6-dichloro-3-hydroxymethylpyridine was as follows: to a solution of (2,6-dichloropyridin-3-yl)methanol (1.0 g, 5.62 mmol) in dichloromethane (10 ml) was added Dess-Martin reagent (4.8 g, 11.24 mmol) at 26 °C. After addition, the reaction mixture was stirred at room temperature for 2 hours. Upon completion of the reaction, the reaction was quenched by addition of 5% Na2S2O3 aqueous solution and stirring was continued for 30 min. The reaction mixture was extracted with dichloromethane (2 x 30 ml). The organic layers were combined and washed sequentially with saturated Na2S2O3 solution (50 ml), brine (30 ml), dried over anhydrous Na2SO4, and concentrated under reduced pressure to afford the crude 2,6-dichloro-3-pyridinecarboxaldehyde (800 mg, 80% yield), which was used directly in the next step of the reaction. The product was characterized by 1H NMR (400 MHz, CDCl3): δ 10.38 (s, 1H), 8.19 (d, J = 8.0Hz, 1H), 7.44 (d, J = 8.0Hz, 1H).
