Metformin Hydrochloride → HCID 178484382, compound

2 kg (1 equivalent) of metformin hydrochloride and 483 g (1 equivalent) of sodium hydroxide were stirred in 10 L of methanol for 2 hours at room temperature, and then remaining solid was filtered and the filtrate was concentrated under reduced pressure. Then 15 L of acetone was added to the resulting solid and stirred. Insoluble material was filtered, and the filtrate was concentrated under reduced pressure to obtain 1,230 g of metformin free base. The metformin free base was dissolved in 33 L of acetone, 2.8 L (4 equivalents) of acetic acid was added, and then the mixture was stirred for 2 hours at room temperature. The resulting crystal was filtered, and re-crystallized in water and acetone to obtain 1,089 g of metformin acetate (yield: 47.7%).