The sequential ester dienolate [2,3]-Wittig/3-oxy-Cope rearrangement. New access to substituted alpha-keto esters

The dienolate [2,3]-Wittig rearrangement of 2-allyloxy-substituted alpha,be ta-unsaturated esters 1a-h afforded 3- alkoxycarbonyl-3-hydroxy-substituted 1,5-hexadienes 4a-h which were transformed to alpha-keto esters 5a-h via a thermal or Pd(II)-catalyzed oxy-Cope rearrangement. Examples for a domino dienolate [2,3]-Wittig / 3-oxy Cope rearrangement and for a domino oxy-Cope rearrangement / ene reaction are reported.