1839-17-4

The general procedure for the synthesis of 3-amino-4-(methylamino)pyridine from 4-methylamino-3-nitropyridine was as follows: 4-methylamino-3-nitropyridine (49.43 g, 0.323 mol) was suspended in methanol (500 mL) under vigorous stirring. Activated charcoal (2.0 g) was added to the suspension and the reaction was refluxed for 2.5 h, followed by standing overnight at room temperature. After flushing the reaction apparatus with dry nitrogen, palladium/carbon catalyst (10% Pd/C, 4.9 g) was added to the mixture. The mixture was bubbled with hydrogen gas for 21 hours at room temperature and under stirring conditions. Upon completion of the reaction, the mixture was filtered through a column of diatomaceous earth (upper layer, 3 cm) and silica gel (lower layer, 5 cm, 13 cm diameter) to remove the catalyst. The filtrate was washed with methanol (3 x 300 mL). The filtrate was concentrated under reduced pressure to afford 3-amino-4-(methylamino)pyridine (39.54 g, 99.5% yield, 0.32 mol) as a brown crystalline solid. The resulting product could be used directly in the subsequent reaction without further purification.

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[3] Patent: WO2015/153683, 2015, A1. Location in patent: Paragraph 0537
[4] Patent: US5371086, 1994, A
[5] Patent: US5262415, 1993, A