Formation of an 6α, 14‐epoxy‐bridged isomorphinan, an unusual product from a substituted 6α,14‐dihydroxymorphinan

During alkylation of 3‐ O ‐benzyl‐6α‐naltrexol ( 1 ) with large aralkyl halides like 2‐bromomethylnaphthalene and 9‐chloromethylanthracene under phase transfer catalysis conditions (potassium hydroxide, tetrabutylammonium bromide, methylene chloride), formation of a new 6α,14‐epoxide‐bridged isomorphinan ( 4 ) was noted. Chemical and spectral evidence, including nmr and mass spectral data, are presented to prove its structure. Its formation results from 6α‐oxygen displacement of a 14‐ O ‐aralkyl ether intermediate under the phase transfer catalysis alkylation conditions.