A facile synthesis of naturally occurring binaphthoquinones: efficient oxidative dimerization of 4-alkoxy-1-naphthols using silver(II) oxide–40% nitric acid

Oxidation of 4-alkoxy-1-naphthols with AgO–40% HNO3 occurred along with a dimerization to give the corresponding bi-1,4-naphthoquinones. The oxidative dimerization required one hydroxyl group and took place at its ortho position. This reaction was applicable to syntheses of naturally occurring binaphthoquinones, bivitamin K3 and 3,3′-bijuglone.