Propiolic Acid → 2-cyano-3-hydroxy-N-(4-trifluoromethylphenyl)-penta-2,4-dienamide

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Reaction Steps

5.0 g (0.22 mole) of 4'-trifluoromethyl-cyanoacetanilide in 150 ml of dry tetrahydrofuran were stirred at room temperature under nitrogen and treated with 2.0 g (0.066 mole) of sodium hydride 80% oil dispersion. The suspension was stirred for 1 hour at room temperature and then was cooled to -70° C. The flask was equipped with an acetone/dry ice condenser and used as the collecting flask from a distillation apparatus charged with 3.01 ml (0.05 mole) of propiolic acid and 15 g of benzoyl fluoride (0.12 mole), as described in J.A.C.S. (1974), Vol. 96 (18), p. 5855 to 5859. The distillation flask was heated in an oil bath at 50° C. and the liberated propynoyl fluoride passed via an air condenser directly into the cold solution of the carbanion. The mixture was stirred at -70° C. for 1 hour and was then quenched by pouring onto a mixture of dilute hydrochloric acid/ice. The mixture was extracted with ethyl acetate and the extracts were dried over magnesium sulfate. The solvent was removed under reduced pressure and triuration with diethyl ether gave colorless crystals of the title compound. Chromatography of the mother liquors over silica gel, eluting with dichloromethane isolated 2.49 g (40%) of the remainder of the product.

Provenance & Evidence