Acetonyltriphenylphosphonium chloride → 7-chloro-4,5-dihydro-3-[(E)-3-oxo-1-butenyl]-5-methyl-6H-imidazo[1,5-a][1,4]benzodiazepin-6-one

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Reaction Steps

10.3 g (29 mmol) of acetonyltriphenylphosphonium chloride are suspended in 100 ml of tetrahydrofuran under argon. 3.3 g (29.4 mmol) of potassium tert.-butylate was added thereto and the mixture was thereafter stirred at room temperature for a further 30 minutes. After cooling to 10° 4.0 g (14.5 mmol) of 7-chloro-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5-a][1,4]benzodiazepine-3-carboxaldehyde was added thereto and the mixture was stirred at 20° for 1 hour and under reflux for 6 hours. The reaction mixture was evaporated, the residue was partitioned between methylene chloride and water, the organic phase was washed with water and subsequently dried over magnesium sulphate, filtered and evaporated. After chromatography of the residue on silica gel with methylene chloride/ethyl acetate (8:2, 7:3 and 1:1) and subsequent recrystallization of the combined pure fractions from ethyl acetate/hexane there was obtained 7-chloro-4,5-dihydro-3-[(E)-3-oxo-1-butenyl]-5-methyl-6H-imidazo[1,5-a][1,4]benzodiazepin-6-one as white crystals of melting point 235°-237°.

Provenance & Evidence