Ferric hydrogensulfate catalyzed aerobic oxidative coupling of 2-naphthols in water or under solvent free conditions

The symmetric oxidative coupling reactions of 2-naphthol derivatives with both ferric hydrogensulfate in water and silica ferric hydrogensulfate in solvent free conditions were carried out. The advantages of this green procedure are: inexpensive catalyst or co-catalyst, reusability of catalyst, organic solvent-free procedures and simple workup.