A novel oxidative cyclization of quinone-arenols 5 leading to products 6 with a dibenzofuran-1,4-dione structure, which forms the core of several natural products, has been developed and applied to the synthesis of violet-quinone (4).

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We investigated the reactions of various 1-naphthols (NPOHs; 1) with p-benzoquinones (Qs), such as 1,4-benzoquinone (BQ) and p-chloranil (CA), as p p-electron acceptors. With electron-rich NPOHs 1a-c, oxidative biaryl coupling and subsequent dehydrogenation reaction took place selectively to give the corresponding 2,2Ј-binapthyl-1,1Ј-quinones 3a-c in excellent yield. In the case of electron-deficient NPOHs 1e, f, two different types of reactions occurred in the presence of SnCl 4 and ZrO 2 under similar conditions: SnCl 4 mediated oxidative dimerization and trimerization of NPOH, while ZrO 2 promoted electrophilic arylation of Qs with NPOH. The resulting products 3 would be useful synthetic intermediates for naturally occurring diosindigo B, biramentaceone and violet-quinone.