Kinetic studies on the rearrangement of Diels–Alder adducts of activated benzoquinones with (E)-1-trimethylsiloxybuta-1,3-diene

Abstract

The acid-induced rearrangement of the 4a-derivatives of 4a,5-trans-4a,8a-cis-5-trimethylsiloxy-4a,5,8,8a-tetrahydro-1,4-naphthoquinones 4–6 in dioxane–water and THF–water solutions is the subject of a kinetic study. On the basis of spectrophotometric evidence, the incursion of 5-hydroxy-tetrahydronaphthalene-1,4-dione and arylcrotonaldehyde type intermediates in formation of the benzofuran from adducts 4–6, is proposed. The effects on the reactions of the solvent composition, temperature, hydrochloric acid concentration, and substituent nature in the adducts are discussed. The results are rationalized and a schematic representation is provided.