[Bmim]PF6/RuCl3·xH2O: a novel and recyclable catalytic system for the oxidative coupling of β-naphthols

Abstract

2-Naphthols readily undergo oxidative coupling in the presence of RuCl₃·xH₂O in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF₆) ionic liquid under aerobic conditions to afford binaphthols in excellent yields with high selectivity. The β-naphthols show enhanced reactivity in ionic liquids, thereby reducing reaction times and improving the yields significantly. The recovered ionic liquid containing ruthenium catalyst can be reused in three to four successive runs with a gradual decrease in activity.