Oxidation of alkoxyphenols. Part XVIII. Further examples of epoxide formation on autoxidation of moderately hindered phenols
Autoxidation of 4,6-di-t-butylguaiacol (I) yields mainly 5,6-epoxy-4-hydroxy-2-methoxy-4,6-di-t-butylcyclohex-2-enone (III) and 2,5-dihydro-5-oxo-2,4-di-t-butylfuran-2-acetic acid (IV), and autoxidation of 5-methoxy-2,4-di-t-butylphenol (II) gives some 5,6-epoxy-4-hydroxy-3-methoxy-4,6-di-t-butylcyclohex-2-enone (XIX) as well as 4-hydroxy-5-methoxy-2,4-di-t-butylcyclohexa-2,5-dienone (XX).
E.s.r. examination of these oxidations reveals the formation of 6-hydroxy-2-t-butyl-1,4-benzosemiquinone during autoxidation of phenol (I), and of 2-hydroxy-3,5-di-t-butyl-1,4-benzosemiquinone during autoxidation of phenol (II). The transformation of compound (XX) into 2,5-di-t-butyl-1,4-benzosemiquinone is also observed by this method.