Catalytic Asymmetric [8+2] Annulation Reactions Promoted by a Recyclable Immobilized Isothiourea

Higher order cycloadditions constitute an efficient approach towards the construction of medium to large ring systems. However, enantioselective versions of these transformations remain scarce, which hampers their deployment in medicinal chemistry, or any other discipline where homochirality is deemed crucial. Herein, we report a novel methodology for the production of enantioenriched cycloheptatrienes fused to a pyrrolidone ring, based on an isothiourea-catalyzed periselective [8+2] cycloaddition between chiral ammonium enolates (generated in situ from carboxylic acids) and azaheptafulvenes. The resulting bicyclic compounds can be hydrogenated, but most remarkably, they can undergo a completely regioselective [4+2] cycloaddition with active dienophiles to give rise to architecturally complex polycyclic compounds in a straightforward manner.