Synthesis
General procedure for the synthesis of 5-ethylpyridin-2-amine from 2-amino-5-bromopyridine and diethylzinc: diethylzinc (24 mL, 1 M hexane solution, 24 mmol) was slowly added dropwise to a solution containing 2-amino-5-bromopyridine (2.0 g, 11.6 mmol) and Pd(dppf)Cl2-CH2Cl2 (225 mg, 0.28 mmol) in a degassed dioxane (45 mL) in solution. The reaction mixture was stirred at room temperature for 2 hours, followed by heating and refluxing for 3 hours and continued stirring at room temperature for 70 hours under argon protection. Upon completion of the reaction, the mixture was poured into saturated aqueous sodium chloride solution (150 mL) and extracted with ethyl acetate (4 x 100 mL). The organic phases were combined, washed with saturated aqueous sodium chloride solution (100 mL), dried over anhydrous sodium sulfate and concentrated under reduced pressure. The crude product was purified by column chromatography (ethyl acetate/heptane followed by methanol/ethyl acetate) to afford the target compound 5-ethylpyridin-2-amine. Yield: 1.40 g (99%).1H NMR (DMSO-d6, 400 MHz) δ 7.74 (s, 1H), 7.25 (dd, 1H), 6.40 (d, 1H), 5.67 (br.s, 2H), 2.39 (q, 2H), 1.10 (t, 3H).
References
[1] Patent: WO2007/51981, 2007, A1. Location in patent: Page/Page column 60
[2] Patent: WO2007/51982, 2007, A1. Location in patent: Page/Page column 52
