Catalytic Asymmetric [8+3] Annulation Reactions of Tropones or Azaheptafulvenes with meso‐Aziridines.

Abstract: Highly enantioselective [8+3] high‐order cycloaddition reactions of tropones or azaheptafulvenes with meso‐aziridines were achieved by a desymmetrization/annulation process in the presence of chiral N,N′‐dioxide/Mg(OTf)2 complex. The corresponding tetrahydrocyclohepta[b][1,4]oxazines and tetrahydro‐1H‐cyclohepta‐ [b]‐pyrazines were obtained in good yields (66–98 %) with excellent diastereo‐ and enantioselectivities (>19:1 d.r., 90–96 % ee). A possible transition state model was proposed to elucidate the origin of chiral induction based on the control experiments and X‐ray crystal structure of the catalyst. [ABSTRACT FROM AUTHOR]