To a solution of 2′,5′-dichloro-3,5-dimethyl-2,4′-bipyridine (4.5 g, 17.8 mmol) and tert-butyl piperazine-1-carboxylate (4.0 g, 21.4 mmol) in DMSO (80 mL) was added CsF (5.4 g, 35.6 mmol). Then the mixture was heated at 120° C. for 18 hours. TLC (petroleum ether/EtOAc=2:1) showed that the reaction was complete. It was diluted with EtOAc (200 mL), washed with H2O (70 mL) and brine (70 mL), dried over Na2SO4 and concentrated in vacuo. The residue was purified by chromatography on silica gel (petroleum ether/EtOAc=3:1) to afford title compound (5.6 g, 78%) as white solid.
