Peroxy esters—III: Acid-catalyzed reaction of 4-hydroperoxy-2,5- cyclohexadienones and their derivatives

Acid-treatment of 4-hydroperoxy-2,5-cyclohexadienones (peroxy-p-quinols) and their acetates leads to the corresponding quinoxy cations through a protonation at the peroxy group, giving rise to different types of products depending on the structure of the peroxy esters. 2,4,6-Trialkyl-p-quinoxy cations undergo a rearrangement with ring opening to give 4-oxa-2-cyclopentenone derivatives, except for p-quinoxy cations with t-butyl or benzyl groups at the 4-position where 2,6-di-t-butyl-p-benzoquinone is exclusively obtained. p-Quinoxy cations with aromatic substituents at the 4-position undergo migration of this substituent to the cationic oxygen. In the case of peroxy-p-quinols (even peroxy-p-naphthoquinols) with 4-aryl substituents the protonation occurs at either O atom of the peroxy bond. Peroxy-p-quinols and their acetates with an unhindered dienone system are quite stable towards acid treatment, probably due to a competitive protonation of the peroxy and the dienone CO group. In solvents containing an oxygen function the reaction proceeds slowly.