General procedure for the synthesis of 2-acetyl-6-bromopyridine from 2,6-dibromopyridine and N,N-dimethylacetamide: 2,6-dibromopyridine (10.0 g, 42.2 mmol) was placed in a dry reaction flask. To ensure an inert atmosphere, the reaction flask was evacuated and replaced with nitrogen and repeated three times. 150 mL of anhydrous diethyl ether was added to the reaction flask and after cooling to -78 °C, n-butyllithium solution (17.7 mL, 44.3 mmol, 2.5 M in n-hexane) was slowly added dropwise and the color of the mixture was observed to change from clear to yellowish brown. Maintained at -78 °C and stirred continuously for 30 min. Subsequently, N,N-dimethylacetamide (4.7 mL, 50.7 mmol) was added slowly and the reaction was maintained at -78 °C for 3 hours. Upon completion of the reaction, the temperature was slowly increased to 20 °C, at which point the color of the mixture changed to a turbid gray. The reaction was quenched by the slow addition of deionized water. The solvent was removed by rotary evaporation and the residue was washed several times with ethyl acetate and saturated sodium chloride solution, the organic layers were combined and dried over anhydrous sodium sulfate. The crude product was purified by silica gel column chromatography (eluent: ethyl acetate/hexane=1:20) and then recrystallized in a mixture of dichloromethane and n-hexane solvent (dichloromethane/hexane=1:20) to give a white crystalline product (6.80 g, 81% yield). The product was characterized by 1H NMR (400 MHz, CDCl3): δ 7.97 (dd, J=7.0,1.6Hz, 1H), 7.68 (t, J=7.8Hz, 1H), 7.64 (dd, J=8.0,1.2Hz, 1H), 2.69 (s, 3H), and was confirmed as the target compound 2-acetyl-6-bromopyridine.
