A new methodology for ring enlargements by the oxy-Cope rearrangement: Ready access to highly functionalized medium-size rings

Highly functionalized cyclononenones, -decenones and -undecenones 14-19 wer e prepared via a sequence of twofold Heck reaction on 1,2-dibromocycloalken es 1-3 to yield (E,Z,E)-1,3,5-hexatrienes 4-6, subsequent epoxidation of th e central double bond leading to the formation of epoxides 7-9, reductive r ing opening of the epoxides and oxyanion-accelerated Cope rearrangement. Th e stereochemical outcome of the rearrangements was highly dependent on the ring size and, particularly in the case of the cyclodecenones, on the react ion conditions. Moreover, these transformations proved to be the first exam ples of reversible anionic oxy-Cope rearrangements. Conversions in the pres ence of benzyl halides led to formation of benzylated cycloalkenones 28-31 via a domino process of rearrangement and alkylation of an intermediate eno late.