Formamide → Imiquimod

Participants

Reaction Conditions

Reaction Steps

A mixture of 4-chloro-1-isobutyl-1H-imidazo[4,5-c]-quinoline (50.0 g, 0.192 mol) and formamide (125 ml, 3.136 mole, 16.3 equiv.) was heated at about 140° C. under nitrogen atmosphere for 26 hours. Then, the reaction mixture was cooled to 95° C. and water (10 ml) was added. The reaction mixture was heated at this temperature for 2 hours. Water (250 ml) and 47% aqueous sodium hydroxide solution were then added to produce a pH of about 9 and the mixture was stirred at ambient temperature for 2 hours. A solid was collected by filtration, washed with water (3×50 ml) and methanol (3×50 ml) and dried at 50° C. under reduced pressure overnight to give crude 4-amino-1-isobutyl-1H-imidazo[4,5-c]quinoline (Imiquimod) (39.0 g). The crude compound (39.0 g) was slurried in a mixture of methanol (500 ml) and 47% aqueous sodium hydroxide solution (about 33.0 ml) under reflux for 6 hours. The mixture was cooled to ambient temperature and a colorless solid was collected by filtration, washed with methanol (3×20 ml), water (3×20 ml) and methanol (3×20 ml) and dried at 50° C. under reduced pressure overnight to yield 22.0 g of Imiquimod in 47.6% yield, having a purity of 98.2% (by HPLC). The product was crystallized from N,N-dimethylformamide to afford colorless Imiquimod having a purity of 99.9% (by HPLC).

Provenance & Evidence