A suspension was prepared from 2-amino-4-bromopyridine (1) (1.00 g, 5.78 mmol) and pyridine-3-boronic acid (2) (1.06 g, 8.67 mmol) in toluene (60 mL). To this suspension, 2N Na2CO3 aqueous solution (20 mL, 0.04 mol) was added, followed by purging the reaction system with nitrogen. Bis(diphenylphosphino)ferrocene palladium(II) chloride dichloromethane complex [abbreviated as "PdCl2(dppf)"] (0.17 g, 0.21 mmol) was added as a catalyst, and the reaction mixture was refluxed under nitrogen protection for 1.5 hours. Upon completion of the reaction, it was diluted by addition of ethyl acetate, the organic phase was washed with water and dried with anhydrous Na2SO4. The solvent was removed by concentration under reduced pressure and the residue was adsorbed on silica. Purification by silica gel column chromatography with MeOH/EtOAc (1:15) as eluent afforded the target product 3,4'-dipyridin-2'-amine (3) as a powdered solid (0.87 g, 87% yield). detected by APCI-MS: [M+H]+=172.
