Reaction of 3-(polyfluoroacyl)chromones with hydrazines: new regioselective synthesis of RF-containing pyrazoles

Reactions of 3-(polyfluoroacyl)chromones with hydrazine, methyl-and phenylhydrazines proceed by the mechanism of nucleophilic 1,4-addition with subsequent pyrone ring opening and heterocyclization at the polyfluoroacyl group to 4-(2-hydroxyaroyl)-3-polyfluoro-alkylpyrazoles or at the aroyl group to 4-polyfluoroalkyl-2,4-dihydrochromeno[4,3-c]pyrazol-4-ols. Regiochemistry of the products was established based on the data of 2D-experiments HSQC, HMBC, and NOESY and X-ray diffraction study.