Asymmetric Organocatalytic Synthesis of Sulfone‐Containing (Dihydro)pyrans via Formal (4 + 2)‐Cycloadditions of Allenylsulfones or Propargylsulfones and Michael Acceptors

Abstract The activation of electron‐poor allenes with Lewis's base catalysts allows for unique transformations and chiral isochalcogenoureas were recently introduced as powerful catalysts for allenoate‐based (4 + 2)‐cycloadditions. We herein report the use of these catalysts for the activation and control of allenylsulfones and propargylsulfones for asymmetric (4 + 2)‐cycloadditions with Michael acceptors. Based on the reaction conditions, this strategy either gives access to sulfone‐containing dihydropyrans or analogous 4H‐pyrans with high yields and excellent levels of enantioselectivities (up to > 99:1 er).