Steric effects of methoxy-groups in some biphenyls derived from thebaine. Part I. Unbridged biphenyls
Abstract
Optically active 3,4-dimethoxy-2-(5-methoxy-2-vinylphenyl)stilbene (III) and 2′-ethyl-5,6,5′-trimethoxy-2-(β-phenethyl)biphenyl (IV) have been prepared from thebaine and their racemisation has been studied. Compound (IV) and the closely related compound (V) are highly optically stable (Erac∼ 34 kcal mol–1). The stilbene (III) racemises more readily (Erac 27·8 kcal mol–1). Their u.v. spectra and optical stabilities are discussed.