Hydrochloric Acid → 4-Hydroxy-3-(4-trifluoromethyloxyphenyl-carbamoyl)-coumarin

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Reaction Steps

First 5.1 g (0.05 mol) of triethylamine and then, slowly, 10.2 g (0.05 mol) of 4-trifluoromethoxyphenyl isocyanate are added dropwise to 8.1 g (0.05 mol) of 4-hydroxycoumarin in 100 ml of dimethylsulphoxide at room temperature. The temperature thereby rises to 31° C. The reaction mixture is subsequently stirred at room temperature for 5 hours. It is added to a mixture of 250 ml of cold water and 15 ml of concentrated hydrochloric acid, whereupon a white precipitate separates out. The mixture is stirred for 30 minutes, with cooling, and the precipitate is filtered off with suction, rinsed with acid water and dried at 50° C. in vacuo. Recrystallization from 100 ml of dioxane gives 8.3 g (45.6% of theory) of 4-hydroxy-3-(4-trifluoromethyloxyphenyl-carbamoyl)-coumarin of melting point 194°-195° C.

Provenance & Evidence