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

Kohei Fuchibe, Masaki Takahashi, and Junji Ichikawa
Angew. Chem. Int. Ed.
DOI: 10.1002/anie.201206946

We don’t often consider the trifluoromethyl group as a reactive centre. But it is, of course, a highly polarised moiety and, under the right conditions, fluoride can act as a competent leaving group. Ichikawa and coworkers employ hydrazines as nucleophiles in two successive displacements of fluoride from vinyl trifluoromethyl adducts to give 3-fluoropyrazole scaffolds.

After testing other possible reaction pathways, they postulate that the reactive intermediate in the cyclisation step, after loss of the tosyl anion, is an azomethine ylide.

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One thought on “Substitution of Two Fluorine Atoms in a Trifluoromethyl Group: Regioselective Synthesis of 3-Fluoropyrazoles

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