A facile and efficient N-to-C allyl shiftaza-Prins cyclization sequence of cyclic N-2-en-4ynyl-N-1-ynylamides is promoted by iron(III) chloride, generating chloro-containing bridged bicyclic enamines in minutes and in high yields. This reaction involves an unprecedented formation of a ketenimine via Fe(III)-mediated N-to-C allyl rearrangement, followed by aza-Prins cyclization. This sequence can also be applied to the generation of brominated cyclobutenamine derivatives using Fe(III) bromide and N-propargyl-N-1-ynylamides.

An efficient stereoselective synthesis of 7‐(E)‐arylidene‐2‐chloro‐6‐azabicyclo[3.2.1]octanes is described. The aluminum chloride‐promoted cyclization/chlorination of six‐membered ring 3‐enynamides enables a straightforward approach to the 6‐azabicyclo[3.2.1]octane nucleus that is incorporated in many biologically active compounds. Acid treatment of the resultant chlorinated arylideneazabicyclooctanes furnishes 3‐alkanoyl‐4‐chlorocyclohexanamines in excellent yields and high stereoselectivity.magnified image