Trimethylsilyl triflate → Ethyl 3-acetylamino-9-[N-(2-chloro-4-fluorophenyl)sulfamoyl]-1,5-dioxaspiro[5.5]undec-7-ene-8-carboxylate

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Reaction Steps

500 mg (1.19 mmol) of ethyl 6-[N-(2-chloro-4-fluorophenyl)sulfamoyl]-3,3-dimethoxy-1-cyclohexene-1-carboxylate obtained in Example (16a) and 205 mg (1.54 mmol) of N-(2-hydroxy-1-hydroxymethylethyl)acetamide were dissolved in 20 ml of dichloromethane, and 0.84 ml (4.74 mmol) of isopropoxytrimethylsilane and 43 μl (0.24 mmol) of trimethylsilyl trifluoromethanesulfonate were added sequentially with stirring under ice-cooling, followed by stirring for 30 minutes at the same temperature, and further for 66 hours at room temperature. Saturated aqueous sodium hydrogencarbonate was added to the reaction solution and the mixture was extracted with dichloromethane. The organic layer was washed with water and dried over anhydrous magnesium sulfate, followed by concentration under reduced pressure. The residue was subjected to silica gel column chromatography (solvent; ethyl acetate methanol=39:1) to give 288 mg of the title compound as an amorphous substance (yield: 50%).

Provenance & Evidence