Substitution and addition reactions of NF4BF4 with aromatic compounds

Benzene, toluene, and nitrobenzene interact rapidly with NF₄BF₄ in anhydrous HF to give, almost exclusively, fluorine substituted aromatic derivatives. Up to four hydrogens can be replaced in a rapid reaction, before a much slower addition reaction takes over. The direction of the substitution in C₆H₆, C₆H₅CH₃ and C₆H₅NO₂ and the lack of side chain fluorination in C₆H₅CH₃ support an electrophillic substituion mechanism. These rapid substitution reactions are followed by much slower fluorine addition reactions to give the corresponding cyclo-hexadienes and -hexenes. These addition reactions were also studied separately using tetra-, penta- and hexa- fluorobenzene as the starting materials. In these addition reactions, almost no hydrogen substitution occured. The addition of the first pair of fluorines always gave 1,4-cyclohexadienes in which CF₂ group was adjacent to hydrogen on the ring. The addition of the second pair of fluorines resulted in the formation of cyclohexenes. These reactions occured in high yield and offer a controlled, high yield path to dienes. All products were characterized spectroscopically and by comparison to literature data.