Application of the intramolecular wadsworth-emmons reaction to bicyclo[3.3.0]oct - Δ - en - 3 - ones. Synthesis and x-ray structure of a novel

The cyclisation of β,ε-diketophosplionates is shown to provide an expeditious route to bicyclo3.3.0]oct - Δ^1,2 - en - 3 - ones, which lack substitoents at C-2 and C-5. Application of the method to the parent member 12 results in the formation of a novel dimer 16 whose structure has been determined by X-ray crystallography. The dimer is thought to derive from 12 by a double Michael addition sequence involving the allyl anion 13 and the enolate 15.