Selective aliphatic fluorination by halogen exchange in mild conditions

HF-Base media, in particular (HF)₁₀-pyridine or (HF)₃-triethylamine, allow aliphatic chlorine-fluorine exchanges on acid-sensitive molecules. Depending on the nature (pyridine or triethylamine), stoichiometry of the base and temperature, selective mono-, di-, or tri-chlorine-fluorine exchanges on trichloromethyl groups alpha to sulfur, oxygen and carbon atoms can be obtained.