Oxidation of alkoxyphenols. Part 27. The mechanism of formation of dibenzo[d,f][1,3]dioxepins

Abstract

Electron spin resonance, kinetic evidence, and product isolation show that in the oxidation of 4-methoxy-3-t-butylphenol one of the initial products is 2-(4-methoxy-3-t-butylphenoxy)-4-methoxy-5-t-butylphenol. The radical of this compound reacts with another product, 5,5′-dimethoxy-4,4′-di-t-butyl-2,2′-diphenoquinone, to form 2′,5,10′-trimethoxy-3′,4,9′-tri-t-butylspiro(cyclohexa-3,5-diene-1,6′-dibenzo[d,f][1,3]dioxepin)-2-one. It is also shown that, depending on the oxidation procedure used, this reaction may provide the major pathway to this product. The other significant pathway involves the reaction of the diphenoquinone with unoxidized 4-methoxy-3-t-butylphenol.