Rearrangement of morphinandienes in methanesulfonic acid

Abstract

Besides 2-fluoroapocodeine 7, the methanesulfonic acid-induced rearrangement of 6-fluoro-6-demethoxythebaine 2 gave the C-2 substituted apocodeines 8,11 and 20. Analogous rearrangement of thebaine 1 in the presence of alcohols offers a convenient and high-yielding route to the 2-alkoxymorphothebaine 6, 11, 12 and 13. Formation of the products has been explained in terms of nucleophilic substitution of the cationic intermediates 21 and 22 from the acid-catalysed reaction.