Phosphorus oxychloride → 1-Methyl-2[n-(4-cyanophenyl)aminomethyl]benzimidazol-5-yl-sulfonic acid-n-phenyl-n-(2-ethoxycarbonylethyl)amide

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Reaction Steps

2.54 g (6.2 mmol) of 3-nitro-4-methylaminobenzenesulfonic acid-N-phenyl-N-(2-ethoxycarbonylethyl)amide were hydrogenated at room temperature under 5 bar hydrogen pressure over palladium/charcoal (10%) in a mixture of 75 mL of ethanol and 75 mL of dichloromethane. The resulting crude 3-amino-4-methylaminobenzenesulfonic acid-N-phenyl-N-(2-ethoxycarbonylethyl)amide was taken up in 30 mL of phosphorus oxychloride, without purification, then 1.1 g (6.2 mmol) of N-(4-cyanophenyl)glycine were added and the mixture was refluxed for two hours. After cooling to room temperature, the reaction mixture was added to about 70 mL of water with cooling and in this way the excess phosphorus oxychloride was destroyed. The resulting solution was neutralized with solid sodium carbonate and extracted three times with 30 mL of ethyl acetate. After evaporation of the solvent, the crude product was purified by column chromatography (100 g silica gel; eluant: cyclohexane/ethyl acetate=2:3). Yield: 860 mg (26.8% of theory), C27H27N5O3S (517.6); melting point: 188° C.-191° C.; Rf value: 0.52 (silica gel; dichloromethane/methanol=9:1); EKA mass spectrum: (M+H)+=518; (M+Na)+=540.

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