Synthesis
General procedure for the synthesis of 3,4,5-trichloropyridin-2-amine from 2-amino-4-chloropyridine: 2-amino-4-chloropyridine (5.0 g, 0.04 mol) was dissolved in concentrated hydrochloric acid (20 mL) and the solution was cooled to 0 °C in an ice bath. Hydrogen peroxide (8.1 mL, 0.08 mol, 32% aqueous solution) was slowly added to the cooled solution, followed by gradual warming of the reaction mixture to room temperature and continuous stirring for 4 hours. Upon completion of the reaction, the mixture was poured into 100 mL of water and the pH was adjusted to 8 (litmus base) by addition of solid sodium carbonate, followed by extraction with ethyl acetate (3 x 50 mL). The organic phases were combined, dried with anhydrous magnesium sulfate, and the filtrate was filtered and concentrated to give a yellow solid product. Finally, purification by ethanol recrystallization afforded 6.3 g (80% yield) of the target compound 3,4,5-trichloropyridin-2-amine as a white solid with a melting point of 160-162 °C.
