Homologous Mukaiyama Reactions via Trapping of the Nazarov Intermediate with Silyloxyalkenes

Treatment of 1,4-pentadien-3-ones and silyloxyalkenes with BF3·OEt2 at room temperature or lower initiates a domino process consisting of sequential 4π electrocyclization and capture of the resulting cyclopentenyl cation by the electron-rich trap. The overall process furnishes 1,4-dicarbonyl products containing highly substituted cyclopentanones in good yields and with the establishment of up to five new stereocenters.