Synthesis of some phenylazonaphthols in an ionic liquid

Several phenylazonaphthols were prepared in 1-butyl-3-methylimidazolium tetrafluoroborate (an ionic liquid) using a coupling reaction of (4-X-benzene)diazonium tetrafluoroborates (X = H and NO2) with 1- and 2-naphthols and their sodium salts. 1H NMR spectra of the reaction products were measured and results compared with previously published data. The reaction of benzenediazonium tetrafluoroborates with sodium salts of 1- and 2-naphthols in 1-butyl-3-methyl-imidazolium tetrafluoroborate was faster compared with that when 1- and 2-naphthols were used. 4-Nitrobenzenediazonium tetrafluoroborate was much more reactive than benzenediazonium tetrafluoroborate.