329974-09-6

1310-73-2

76-05-1

329974-10-9

329974-09-6

c) Synthesis of 4-bromo-2,6-diaminopyridine 1 g (3.65 mmol) of 4-bromo-pyridine-2,6-dicarboxylic acid dihydrazide was suspended in 32 mL of water and 1.6 mL of 37% HCl was added at room temperature.The reaction mixture was cooled down to 0 °C and 554 mg of NaNO2 dissolved in 2.4 mL of water was slowly added keeping the reaction temperature below 2 °C. The reaction temperature was adjusted to 8 °C by filtration. After completion of the reaction, the pH was adjusted to 8 with saturated NaHCO3 solution, the white precipitate was collected by filtration and washed with cold water. The solid residue was dissolved in CHCl3 and dried with MgSO4. The filtrate was concentrated at 20 °C to give 920 mg (85%) white solid. 450 mg (1.5 mmol) of the above white solid was suspended in a solvent mixture of toluene/tert-butanol (5:1) and refluxed for 12 hours. After removing the solvent under reduced pressure, 5 mL of toluene and 0.3 mL of trifluoroacetic acid were added and reflux was continued for 2 hours. The solvent was again removed under reduced pressure and the residue was purified by rapid chromatography on silica gel using dichloromethane/methanol (9:1) as eluent. After elution the solvent was removed under reduced pressure and the residue was suspended in diethyl ether and a 1N NaOH solution was added to release 4-bromo-2,6-diaminopyridine. The organic phase was dried over Na2SO4 and the solvent was removed under reduced pressure to give 192 mg (67%) of the target product. Mass spectrometry analysis showed m/e: 188 (M+, 100%).