Hydrogen fluoride-pyridine (70% HF)

Convenient form of anhydrous HF, showing increased reactivity in many reactions. Has been used for the preparation of β-fluoroamines from amino alcohols and for the fluorination of acetylenes,^1,2 electrophilic electrochemical fluorination ³ and conversion of carboxylic acids to acyl fluorides.⁴ Used together with hypervalent iodine(III) reagents for ipso-fluorination of para-substituted phenols providing cyclohexadienones.⁵ Employed with Selectfluor™ for geminal fluorination of 2,2-diaryl-1,3-dithiolanes.⁶

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6. Chem. Commun. 2005, 654.