SnCl4-mediated oxidative biaryl coupling reaction of 1-naphthol and subsequent ring closure of 2,2′-binaphthol to the dinaphthofuran framework

A simple method for the direct synthesis of 2,2′-binaphthols and dinaphtho[1,2-b;2′,1′-d]furans under mild conditions was developed, utilizing a biaryl coupling reaction via electron donor–acceptor complexes of 1-naphthols with SnCl4. Heating of the complex in a sealed tube for (18–24 h) afforded the corresponding o–o coupled product in excellent yield. Prolonged reaction (56–65 h) under the same conditions afforded in high yield in one step. We also found that in the case of α-naphthol without substituents other than a hydroxyl group at the C-1 position, regioselective o–o coupling reaction proceeded. The products , and should be useful as synthetic intermediates for naturally occurring 3,3′-bijuglone, 3,3′-biplumbagin and elliptinone.