The synthesis of bicyclo[2.2.2]octenones via intramolecular Diels–Alder reactions of modified Wessely oxidation products

Abstract

"Modified" Wessely oxidation of 2,6-dimethylphenol with lead tetraacetate in the presence of acrylic acid, cinnamic acid, cis-β-bromoacrylic acid, trans-β-bromoacrylic acid, methyl hydrogen maleate, methyl hydrogen fumarate, and tiglic acid followed by intramolecular cycloaddition gives exo-6-hydroxy-4,6-dimethyl-5-oxobicyclo [2.2.2]oct-7-ene-exo-2-carboxylic acid lactones. Analogous products have been obtained from o-cresol. Structural assignments have been made on the basis ofthe ir, uv, and 1H nmr spectra of the products; analysis of the last shows that the geometry of the bicyclo[2.2.2]octenone system is distorted by the presence of the lactone ring. Chemical transformations of two of the products from the "modified" Wessely oxidation–intramolecular cycloaddition sequence have demonstrated that this route may be used to prepare regioisomers or stereoisomers of products obtained by the conventional Wessely oxidation–intermolecular cycloaddition sequence.