Hydrochloric Acid → Pyrimido(1,6-a)benzimidazole-1,3(2H,5H)-dione, 5-cyclopropyl-8-fluoro-2-hydroxy-7-(1-piperazinyl)-, monohydrochloride

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Reaction Steps

tert-Butyl 4-[5-cyclopropyl-8-fluoro-1,2,3,5-tetrahydro-2-hydroxy-1,3-dioxopyrimido[1,6-a]benzimidazol-7-yl]-1-piperazinecarboxylate (350 mg, 0.76 mmol) is treated with a 2.5N hydrochloric acid solution in dioxane (4 ml), whereby a white precipitate forms immediately. The suspension is stirred at room temperature (25°) for 18 hours. The separated crystals are filtered off and dissolved in water (10 ml). The solution is treated with active charcoal, then filtered and cooled to 0°. The separated crystals are filtered off, washed with ethanol and ether and dried in a high vacuum. There are obtained 176 mg (58%) of 5-cyclopropyl-8-fluoro-2-hydroxy-7-(1-piperazinyl)-pyrimido[1,6-a]benzimidazole-1,3(2H,5H)-dione hydrochloride.

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