Dienone–phenol rearrangement mechanism of 8,8-dimethyl- and 6,8,8-trimethyl-naphthalene-1,4,5(8H)-triones in acetic anhydride solution

Abstract

Dienone–phenol rearrangement of 8,8-dimethyl- and 6,8,8-trimethyl-naphthalene-1,4,5(8H)-triones (1) and (2) in acetic anhydride as solvent is the subject of a kinetic study. The effects of sulphuric and acetic acids are also investigated. Both substrates show limiting [H₂SO₄] dependence and an inhibiting effect with acetic acid. The effect of temperature in the reaction of (1) and that of the C-6 methyl group of (2) are discussed. The results are rationalized in terms of the formation of acylated intermediate cations and schematic representation is provided.