Asymmetric [3 + 2] Cycloaddition to Access 3‐Pyrrolines and Their Switchable Transformations to Nine‐Membered Cyclic Sulfamidates and 2 <i>H</i> ‐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 2H-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.