The aryl–aryl coupling reaction of 1-naphthol with SnCl4 for 2,2′-binaphthol synthesis and its application to the biomimetic synthesis of binaphthoquinone isolated from Plumbago zeylanica

A simple method for the direct synthesis of 2,2′-binaphthols was developed, utilizing aryl–aryl coupling reaction via electron donor–acceptor complexes of 1-naphthols with SnCl4. Heating of the complex in a sealed tube afforded the corresponding o-o coupling product in excellent yield. This method was utilized for a biomimetic synthesis of the binaphthoquinone, 3,3′-biplumbagin, isolated from Plumbago zeylanica.