Unexpected Metal-Free Fluorination and Oxidation at the C-4 Position of Pyrazoles Promoted by Selectfluor

Abstract

Metal-free electrophilic fluorination, promoted by Selectfluor, of pyrazoles with methylene groups (CH₂X), in which X = OH, OMe, F, N₃, and NHMe at the C-4 position furnished the 4-fluoro-pyrazole products from unexpected C–C bond cleavage, at moderate to good yields. Otherwise, under the same reaction conditions, when X = NEt₂ or SPr, the oxidation product 4-formyl-pyrazole was obtained.

Key words

electrophilic fluorination - oxidation - Selectfluor - metal-free - pyrazole - hydrazine - Vilsmeier–Haack

• References and Notes

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