Asymmetric [3 + 2] Cycloaddition to Access 3‐Pyrrolines and Their Switchable Transformations to Nine‐Membered Cyclic Sulfamidates and 2 H ‐Pyrroles

Herein, Pd‐catalyzed asymmetric [3 + 2] cycloaddition and olefin isomerization is reported to afford chiral 3‐pyrrolines using cyano‐TMM (trimethylenemethane) and cyclic sulfamidate imines. This represents a unique protocol to provide chiral N ‐heterocycles bearing endocyclic olefins by asymmetric Pd‐TMM cycloaddition. The developed Pd‐catalyzed cycloaddition further extends to versatile synthetic transformations, offering a facile and unified approach to synthetically challenging yet valuable classes of heterocycles, including medium‐sized sulfamidate rings and 2 H ‐pyrroles, in a one‐pot operation. In particular, chemo‐switchable ring expansion and desulfonylation of sulfamidate‐fused 3‐pyrrolines are achieved by simple solvent and temperature changes under identical alkoxide base conditions.