Aerobic oxidative coupling of 2-naphthols by simple copper salts: A highly efficient catalytic system in the absence of ligand or carrier

Abstract

A ligand-free or carrier-free copper salt system that catalysed aerobic oxidative coupling of 2-naphthols has been established. 1,1′-Bi-2- naphthols were afforded in excellent yields in methanol in the presence of 5 mol % copper (| or ∥) salts. The coupling reaction could also be performed very well in aqueous solvents.