[Br:1][C:2]1[C:7]2[C:8](=[O:24])[N:9]3[CH2:23][CH2:22][CH2:21][C@H:10]3[C:11]3[N:12]([CH:13]=[N:14][C:15]=3[C:16]([O:18][CH2:19][CH3:20])=[O:17])[C:6]=2[CH:5]=[CH:4][CH:3]=1.O[CH2:26][CH:27]1CC1.[C-]#N.[K+]>>[Br:1][C:2]1[C:7]2[C:8](=[O:24])[N:9]3[CH2:23][CH2:22][CH2:21][C@H:10]3[C:11]3[N:12]([CH:13]=[N:14][C:15]=3[C:16]([O:18][CH2:19][CH:20]3[CH2:27][CH2:26]3)=[O:17])[C:6]=2[CH:5]=[CH:4][CH:3]=1A mixture of 12 g (31 mmol) of ethyl (S)-8-bromo-11,12,13,13a-tetrahydro-9-oxo-9H-imidazo[1,5-a]pyrrolo[2,1-c][1,4]benzodiazepine-1-carboxylate, 60 ml (750 mmol) of hydroxymethyl-cyclopropane and 500 mg of powdered potassium cyanide is stirred at 135° for 1.5 hours, the alcohol being simultaneously distilled off over a Hickmann headpiece and a 15 cm Vigreux column. The mixture is evaporated to dryness, the residue is taken up in chloroform, washed with water, dried over magnesium sulphate and evaporated. By recrystallization from ethyl acetate there is obtained cyclopropylmethyl (S)-8-bromo-11,12,13,13a-tetrahydro-9-oxo-9H-imidazo[1,5-a]pyrrolo[2,1-c][1,4]benzodiazepine-1-carboxylate of melting point 135°-136°.
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