Solvent-free synthesis of 1, 1'-bi-2-naphthanol by ball milling

1, 1'-Bi-2-naphthanol is prepared with yield of 91% by the coupling of β-naphthol under solvent-free condition in ball mill using CuCl₂·2H₂O as an oxidant. The optimum conditions are given as follows: 1:12 of the ratio of CuCl₂·2H₂O and β-naphthol by molar and 350 r/min of the rotational speed of the ball mill for 2 hours. The effect of other oxidants of Cu(II)/Fe(III) on the coupling of β-naphthol is investigated as well. The chemical structure of the product is characterized by IR and 1H-NMR.