Renewable Reagent for Nucleophilic Fluorination

Herein, we report a study on the reactivity of three1,3-diarylimidazolium-basedfluoride reagents, with a generalformula of [IPrH][F(HF)n](n= 0, 1, or 2), that tackle thechallenges of limited solubility, hygroscopicity, instability, andlaborious preparation procedures of nucleophilicfluoride reagents.Fluorination of 4-tert-butylbenzyl bromide reveals that trifluoride[IPrH][F(HF)2] is the most selective reagent. Microwave-assistedactivation coupled with the addition of sterically hindered amineDIPEA or alkali metalfluorides increases the rate offluorinationwith [IPrH][F(HF)2], making it an excellent reagent for thefluorination of various organic substrates. The scope of substratesincludes benzyl bromides, iodides, chlorides, aliphatic halides,tosylates, mesylates,alpha-haloketones, a silyl chloride, acyl andsulfuryl chlorides, and a nitroarene. The exceptional stability of the air-stable and nonhygroscopic [IPrH][F(HF)2] reagent isillustrated by its convenient synthesis and detailed experimental regeneration protocol using hydrofluoric acid without organic solvents

Automated summary

This study investigated the reactivity of three 1,3-diarylimidazolium-based fluoride reagents in fluorination reactions, highlighting the trifluoride [IPrH][F(HF)2] as the most selective and stable reagent for various organic substrates. The use of microwave-assisted activation and steric hindrance resulted in increased fluorination rates, showcasing the potential of [IPrH][F(HF)2] as an excellent reagent in organic synthesis.