Synthetic Methods and Reactions. 63. Pyridinium Poly(hydrogen fluoride)(30% Pyridine-70% Hydrogen Fluoride): A Convenient Reagent for Organic Fluorination Reactions

Pyridinium poly(hydrogen fluoride) (30% pyridine-70% hydrogen fluoride) reagent, a stabilized, less-volatile form of hydrogen fluoride, was found to be a convenient and effective fluorinating agent. Fluorination, halofluorination, nitrofluorination, and hydrofluorination of olefins were achieved using the reagent. The in situ diazotization and subsequent fluorinative dediazonization of α-amino acids, aminoarenes, and carbamates yielded α-fluorocarboxylic acids, aryl fluorides, and fluoroformates, respectively. Geminal dihalides and α-halo ketones were reacted with mercuric oxide in pyridinium poly(hydrogen fluoride) to form geminal difluorides and a-fluoro ketones. Solutions of alkali halides in pyridinium poly(hydrogen fluoride) were also found to be effective halogenating agents for aminoarenes, via in situ diazotization and subsequent nucleophilic dediazonization by the corresponding halides, as well as for alcohols, via S_N2 type displacement reactions. Diazo ketones and diazoalkanes also reacted smoothly with halide ions in pyridinium poly(hydrogen fluoride) solution to give the corresponding geminally halofluorinated compounds.