S. Berenyi et al., MORPHINE ALKALOIDS .121. REARRANGEMENT OF MORPHINANDIENES IN METHANESULFONIC-ACID, Journal of the Chemical Society. Perkin transactions. I, (17), 1993, pp. 2137-2139
Besides 2-fluoroapocodeine 7, the methanesulfonic acid-induced rearran
gement of 6-fluoro-6-demethoxythebaine 2 gave the C-2 substituted apoc
odeines 8, 11 and 20. Analogous rearrangement of thebaine 1 in the pre
sence 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 i
ntermediates 21 and 22 from the acid-catalysed reaction.