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Substitution of Two Fluorine Atoms in a Trifluoromethyl Group: Regioselective Synthesis of 3-Fluoropyrazoles

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  • We acknowledge the Grants-in-Aid for Scientific Research on Innovative Areas “Organic Synthesis Based on Reaction Integration. Development of New methods and Creation of New Substances” (No. 2105) for financial support. We also thank Tosoh F-TECH, Inc. for the generous gift of2-bromo-2,2,2-trifluoroprop-1-ene.

Abstract

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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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