The general procedure for the synthesis of 6-chloro-2-methylpyrimidine-4,5-diamine from 2-methyl-4,6-dichloro-5-aminopyrimidine is as follows:
1. Preparation of 6-chloro-4,5-diamino-2-methylpyrimidine. To a 200 mL stainless steel Parr reactor was added 5-amino-4,6-dichloro-2-methylpyrimidine (7.2 g, 40 mmol) and an isopropanol solution of 2M ammonia (100 mL) and the reactor was sealed. The reaction mixture was heated at 150°C for 16 hours. Complete reaction was confirmed by HPLC analysis. After completion of the reaction, the mixture was concentrated under vacuum to obtain the residue. The residue was suspended in a solvent mixture of water (10 mL) and isopropanol (35 mL), stirred at 50°C for 1 hour, and then cooled to room temperature. The precipitate was collected by filtration, washed with a small amount of isopropanol and air dried over a filter to afford 6-chloro-4,5-diamino-2-methylpyrimidine (5.8 g, 91% yield) as a brown powder, which could be used in the next reaction without further purification.
