Hydrochloric Acid → 5-aminocarbonylamino-1-{1-[4-(4-amino-3,5-dibromophenyl)-4-oxobutyl]-4-piperidinyl}-1,3-dihydro-2(2H)-benzimidazolone

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Reaction Steps

1.5 ml of 1N hydrochloric acid, followed by 47 mg (0.723 mmol) of sodium cyanate were added to a solution of 200 mg (0.363 mmol) of 5-amino-1-{1-[4-(4-amino-3,5-dibromophenyl)-4-oxobutyl]-4-piperidinyl}-1,3-dihydro-2(2H)-benzimidazolone in 5 ml of THF at a reaction temperature of 0° C. The ice bath was removed and the mixture was stirred overnight at ambient temperature. The orange-coloured solution was carefully combined with 100 ml of conc. aqueous sodium hydrogen carbonate solution and overlaid with 50 ml of tert.butylmethyl ether. The precipitate formed was suction filtered and purified by column chromatography on silica gel (30–60 μm) using dichloromethane/methanol/cyclohexane/conc. ammonia 400/40/40/2.5 v/v/v/v as eluant. By working up the appropriate fractions 106 mg (44% of theoretical) of the desired compound were obtained in the form of colourless crystals (THF/diethylether 1/1 v/v)), Rf 0.12 (El B). IR (KBr): 3435.0, 3354.0 (NH, NH2); 1701.1, 1662.5 (C═O) MS: ESI: (M+H)+=593/595/597 (Br2); (M+Na)+615/617/619 (Br2)

Provenance & Evidence