Oxidation of alkoxyphenols. Part VIII. Further examples of trimerisation to spiroketals

Abstract

The formation of spiroketal trimers (dibenzo[d,f]dioxepins) upon oxidation of alkyl monosubstituted p-methoxyphenols has been shown to be a general reaction. Representative trimers have been hydrolysed, and the methylated reduction product, 2,5,5′-trimethoxy-2′-(2,5-dimethoxy-3-methylphenoxy)-3,3′-dimethylbiphenyl, of one of them synthesised to prove their structure. The formation of dimers in less alkaline solution is also described, and oxidation products of p-alkoxyphenols are reviewed.