Hexane → 1-[[3-(Tert-butyl-dimethylsilanyloxy)propyl)-(4'-fluorobiphenyl-4-sulfonyl)amino]-cyclopentanecarboxylic acid benzyl ester

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Reaction Steps

To a solution of 1-(4'-fluorobiphenyl-4-sulfonylamino)cyclopentanecarboxylic acid benzyl ester (23.0 grams, 50.7 mmol) in dry N,N-dimethylformamide (500 ml) at room temperature was added potassium hexamethyldisilazide (12.2 grams, 61.1 mmole) and, after 45 minutes, tert-butyl-(3-iodopropoxy)dimethylsilane (18.3 grams, 60.9 mmol). The resulting mixture was stirred at room temperature for 16 hours. Additional potassium hexamethyidisilazide (3.0 grams, 15 mmole) and tert-butyl-(3-iodopropoxy)-dimethylsilane (4.5 grams, 15 mmol) were then added. Stirring at room temperature was continued for a further 5 hours. The mixture was quenched by addition of saturated ammonium chloride solution. The N,N-dimethylformamide was removed by evaporation under vacuum. The residue was taken up in diethyl ether and washed successively with water, dilute aqueous hydrochloric acid solution and brine. After drying over magnesium sulfate, the diethyl ether was evaporated to afford a yellow oil. To this was added hexane and methylene chloride to induce crystallization of the starting material which was recovered by filtration. Evaporation of solvents from the filtrate afforded crude 1-[[3-(tert-butyl-dimethylsilanyloxy)propyl]-(4'-fluorobiphenyl-4-sulfonyl)amino]-cyclopentanecarboxylic acid benzyl ester as an amber oil (27.35 grams).

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