Replacing the fluorine: 3-Fluorinated pyrazoles were regioselectively synthesized by sequential substitution reactions of 2-trifluoromethyl-1-alkenes (see scheme). SN2′-type reactions of 2-trifluoromethyl-1-alkenes with deprotonated tert-butoxylcarbonyl- or arylhydrazines afforded 1,1-difluoro-1-alkenes, which were tosylated and then treated with NaH to give the desired 3-fluoropyrazoles.
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