Switchable Chemo‐, Regio‐ and Pseudo‐Stereodivergence in Palladium‐Catalyzed Cycloaddition of Allenes

Abstract Here, we report a strategy enabling triple switchable chemo‐, regio‐, and stereodivergence in newly developed palladium‐catalyzed cycloadditions of allenes. An asymmetric pseudo‐stereodivergent cycloaddition of allenes bearing a primary leaving group at the α ‐position, where a dynamic kinetic asymmetric hydroalkoxylation of racemic unactivated allenes was the enantio‐determining step, is realized, providing four stereoisomers [( Z,R ), ( Z,S ), ( E,S ), and ( E,R )] containing a di‐substituted alkene scaffold and a stereogenic center. By tuning reaction conditions, a mechanistically distinctive cycloaddition is uncovered selectively with the same set of substrates. By switching the position of the leaving group of allenes, a cycloaddition involving an intermolecular O‐attack is disclosed. Diverse mechanisms of the cycloaddition reactions of allenes enable rapid access to structurally and stereochemically diverse 3,4‐dihydro‐2 H ‐1,4‐benzoxazines in high efficiency and selectivity.