Selective Syntheses of Δαβ and Δβγ Butenolides from Allylic Cyclopropenecarboxylates via Tandem Ring Expansion/33-Sigmatropic Rearrangements

摘要

Allylic cyclopropenecarboxylates undergo ring expansion reactions to give 2-allyloxyfuran intermediates, which subsequently rearrange to Δ^β,γ butenolides via Claisen rearrangement or to the corresponding Δ^α,β butenolides via further Cope rearrangement. Also described are methods for chirality transfer in the rearrangement of non-racemic allylic esters.