Water → 2-Chloro-N4-methylpyridine-3,4-diamine

10 g of (10) were dissolved in 50 ml of 12N HCl and the temperature brought to 90° C. 72.5 g di SnCl2.2H2O were added in five portions over the course of 1 minute. This was left stirring at 90° C. for 1 hour. After cooling the solution to room temperature, 100 ml of water were added and evaporated at reduced pressure. The residue was taken up in 100 ml of water, cooled to 0° C. and concentrated aqueous ammonia added, until the formation of a white, gelatinous precipitate. The pH was adjusted to 8.5-9 and the resulting emulsion centrifuged. The remaining solid residues were again taken up in water and centrifuged. The operation was repeated three times. The combined solid residues were left under stirring overnight in 50 ml of methylene chloride. The centrifuged aqueous phases were extracted three times with methylene chloride, then all the organic phases combined, then dried over anhydrous sodium sulphate and subsequently evaporated under vacuum, giving 6.2 g of (11) in the form of pink crystals.