2-Amino-5-bromopyridine → 5-Ethenylpyridin-2-amine

5-Bromopyridine-2-amine (2.51 g) was dissolved in toluene (150 mL), tributylvinyl tin (10.0 g), lithium chloride (1.23 g) and 2,6-di-tert-butyl-4-methylphenol (160 mg) were added and the mixture was heated under reflux for 2 hr 30 min. The resulting solid was removed by filtration, and the solvent was evaporated. The residue was dissolved in ethyl acetate and the insoluble material was removed again by filtration. The filtrate was extracted with 0.2 mol/L hydrochloric acid (100 mL, 50 mL), and the obtained hydrochloric acid solution was basified (pH 12) with 1 mol/L sodium hydroxide, extracted with ethyl acetate (200 mL), and the organic layer was washed with saturated aqueous sodium chloride solution, and dried over anhydrous sodium sulfate. The solvent was evaporated to give 5-vinylpyridine-2-amine (1.00 g). This was dissolved in ethyl acetate (80 mL). Under a nitrogen atmosphere, 10% palladium-carbon (330 mg) was added, and the mixture was stirred under a hydrogen atmosphere for 8 hr. The reaction container was substituted with nitrogen (gas) and 10%-palladium carbon (300 mg) was added. The mixture was stirred under a hydrogen atmosphere for 4 hr. The reaction container was substituted with nitrogen (gas) and the catalyst was filtered off. The solvent was evaporated and the residue was dissolved in 0.4 mol/L hydrochloric acid (20 mL). The obtained hydrochloric acid solution was washed with ethyl acetate, basified (pH 12) with 1 mol/L aqueous sodium hydroxide solution, and extracted with ethyl acetate. The organic layer was washed with saturated sodium chloride aqueous solution, and dried over anhydrous sodium sulfate. The solvent was evaporated to give the title compound (773 mg).