Stereoselective Construction of Bridged trans-aza-Bicyclo[7/6,3/2,1]alkenyl Imines through Ring Expansion aza-Cope Rearrangement.

A highly stereoselective method for efficient synthesis of unprecedented bridged bicyclo[7/6,3/2,1]alkenyl amidines is described using cyclic N-allyl-aminoalkyne as a substrate. A ketenimine formation/cyclization/aza-Cope rearrangement cascade proceeds either with or without the aid of external DIPEA depending on substrate basicity. Fused bicycloamidines are also obtained via the same protocol using different N-allyl cyclic aminoalkynes.