[F:1][C:2]1[CH:3]=[CH:4][C:5]2[N:11]3[CH:12]=[N:13][C:14]([C:15](OCC)=[O:16])=[C:10]3[CH2:9][N:8]([CH3:20])[C:7](=[O:21])[C:6]=2[CH:22]=1.[BH4-].[Li+].O.Cl.O>O1CCCC1>[F:1][C:2]1[CH:3]=[CH:4][C:5]2[N:11]3[CH:12]=[N:13][C:14]([CH2:15][OH:16])=[C:10]3[CH2:9][N:8]([CH3:20])[C:7](=[O:21])[C:6]=2[CH:22]=115.0 g (49.5 mmol) of ethyl 8-fluoro-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5-a][1,4]benzodiazepine-3-carboxylate are dissolved under argon in 450 ml of boiling absolute tetrahydrofuran (filtered over Alox) and added dropwise at 50° C. to a solution of 1.1 g (49.5 mmol) of lithium borohydride in 50 ml of absolute tetrahydrofuran. The mixture is stirred at 40° C. for 4 hours and at the boiling point for 2.5 hours. Subsequently, the mixture is decomposed at 40° C. with 20 ml of water and 20 ml of concentrated hydrochloric acid/water (1:1) and stirred at room temperature overnight. After removal of the tetrahydrofuran in vacuo, the residue is treated with 14 ml of concentrated ammonia. The mixture is left to crystallise in the cold and separated material is filtered off under suction and washed with water. After recrystallisation from ethanol, there is obtained 8-fluoro-4,5-dihydro-3-(hydroxymethyl)-5-methyl-6H-imidazo[ 1,5-a][1,4]benzodiazepin-6-one of melting point 221°-223° C.
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