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

Highly enantioselective [8+3] high-order cyclo-addition 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.