Synthesis
General procedure for the synthesis of 2-amino-3-bromo-4-methylpyridine from 2-amino-3,5-dibromo-4-methylpyridine: 3,5-dibromo-4-methylpyridin-2-amine (3.38 g, 12.7 mmol) was dissolved in dry tetrahydrofuran (60 mL) under the protection of nitrogen, and cooled to -78°C. n-Butyllithium (1.9 M in pentane, 13.4 mL, 25.4 mmol) was added slowly and the reaction mixture turned orange. The reaction was quenched by careful addition of water (10 mL) after 1 h of continuous stirring at -78°C. The reaction was stopped by the addition of a solution of 10 N sodium hydroxide. The pH of the reaction mixture was adjusted to about 12 with 10 N sodium hydroxide solution and then extracted with dichloromethane (3 x 30 mL). The organic phases were combined, dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give an orange oil. Purification by silica gel column chromatography (with ether as eluent) afforded 2-amino-3-bromo-4-methylpyridine (1.68 g, 71% yield) as a light yellow solid.1H NMR (CDCl3) δ 2.32 (s, 3H), 5.00 (br s, 2H), 6.52 (d, 1H, J = 6.0 Hz), 7.84 (d, 1H, J = 6.0 Hz ).
References
[1] Patent: US2005/277668, 2005, A1. Location in patent: Page/Page column 28
[2] Patent: EP3372601, 2018, A1. Location in patent: Paragraph 0693; 0694
