Hydrochloric Acid → 4,5-dihydro-3-(hydroxymethyl)-5-methyl-6H-imidazo[1,5-a][1,4]benzodiazepin-6-one

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Reaction Steps

21.5 g (75.4 mmol) of ethyl 5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5-a][1,4]benzodiazepine-3-carboxylate are dissolved in 250 ml of hot absolute tetrahydrofuran (filtered over Alox basic I) under an argon atmosphere while stirring, cooled to ca 30° C. and treated dropwise with a solution of 1.66 g (75.4 mmol) of lithium borohydride in 25 ml of absolute tetrahydrofuran. The mixture is heated to boiling under reflux for 6 hours, cooled to room temperature and decomposed with 50 ml of 3 N aqueous hydrochloric acid. The mixture is stirred at 60° C. for a further 2 hours and the tetrahydrofuran is removed in vacuo. The residue is made alkaline with concentrated ammonia and left to stand in an ice-bath for 2 hours. The crude product is filtered off under suction, washed with a large amount of water and recrystallised from ethanol. There is obtained 4,5-dihydro-3-(hydroxymethyl)-5-methyl-6H-imidazo[1,5-a][1,4]benzodiazepin-6-one of melting point 224°-226° C.

Provenance & Evidence