The formation of dibenzofurans in acid-catalysed quinone–phenol reactions and quinone oligomerisations: evidence for quinone hemiacetal intermediates

Abstract

The acid-catalysed reductions of (2,4-dihydloxyphenyl)-1,4-naphthoquinone (1) and the quinone hemiacetal (7) by tetramethylhydroquinone furnish the 2-hydroxydibenzofurans (3) and (9), respectively. The quinone (1) reacts with 2-methylresorcinol and 2, 4-dihydroxy-5-methylphenyl-1, 4-naphthoquinone (2) reacts with resorcinol, giving two different methyl substituted dihydroxy(dihydroxyphenyl)benzonaphthofurans (6) and (5), respectively. The hemiacetal (7) and resorcinol give the dihydroxyphenyldibenzofuran (10). These results provide support for the participation of quinone hemiacetals in the acid-catalysed condensation reactions of quinones with phenols to form dibenzofurans.