2,2'-Bipyridine-5-carboxylic acid

58792-53-3

1970-80-5

General procedure for the synthesis of [2,2'-bipyridine]-5-carboxylic acid from methyl [2,2'-bipyridine]-5-carboxylate: first, 2-chloro-5-methoxycarbonylpyridine (1.3 g, 7.6 mmol) was dissolved in 20 ml of mesitylene, PdCl2(PPh3)2 (0.27 g, 0.04 mmol) and 2-trimethylpyridine (2.1 g, 8.6 mmol). The mixture was heated to reflux for 20 hours. After completion of the reaction, it was left to cool, diluted with ether and filtered through a neutral alumina column. The filtrate was washed several times with water and dried with anhydrous sodium sulfate. After evaporation of the solvent, it was purified by silica gel column chromatography to give 1.13 g of compound 10 as a white solid in 70% yield. Subsequently, compound 10 (1.13 g, 5.3 mmol) was suspended in 120 ml of ethanol/water mixed solvent in the ratio of 1:120 and a solution prepared by dissolving KOH (0.35 g, 6.3 mmol) in 2 ml of water was added and the reaction was stirred for 3 hours. After completion of the reaction, the ethanol was removed by distillation and concentration and adjusted to neutral by adding 1 mol/L hydrochloric acid. The resulting suspension was extracted three times with chloroform, the extract was washed with water, dried with anhydrous sodium sulfate and distilled to remove the solvent. The crude product was purified by silica gel column chromatography to afford 0.8 g of compound 11 as a light yellow solid in 75% yield.