To a mixture of 2,3,5,6-tetrachloropyridine (6.51 g), 1-Boc-piperazine (6.71 g) and potassium carbonate (9.95 g) were added dimethylformamide (15 mL) and toluene (30 mL), and the mixture was stirred at 100° C. for 2 hr. After cooling, water was added to the reaction mixture, and the mixture was extracted with ethyl acetate. The organic layer was washed with saturated brine, and dried over sodium sulfate. The solvent was evaporated under reduced pressure and the residue was purified by column chromatography (ethyl acetate:hexane) to give the title compound (9.42 g).
