Treatment of 1,4-pentadien-3-ones and silyloxyalkenes with BF(3)·OEt(2) 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.
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