Lewis Acid‐Catalyzed Unusual (4+3) Annulation of para‐Quinone Methides with Bicyclobutanes: Access to Oxabicyclo4.1.1 octanes

Over the past few years, there has been a surge of interest in the chemistry of bicyclobutanes (BCBs). Although BCBs have been used to synthesize bicyclo2.1.1hexanes and bicyclo3.1.1heptanes, the synthesis of bicyclo4.1.1octanes has remained elusive. Herein, we report the first Lewis acid-catalyzed unexpected (4+3) annulation of para-quinonemethides (p-QMs) with BCBs allowing the synthesis of oxabicyclo4.1.1octanes proceeding under mild conditions. With 5 mol % of Bi(OTf)