Double Strain‐Release (3+3)‐Cycloaddition: Lewis Acid Catalyzed Reaction of Bicyclobutane Carboxylates and Aziridines

Abstract

A (3+3)‐cycloaddition to afford 2‐azabiyclo[3.1.1]heptanes was realized by reacting highly strained aryl bicyclo[1.1.0]butane (BCBs) carboxylates with tosylated aziridines. Under Sc(OTf)3 catalysis the transformation proceeded smoothly under mild conditions to the corresponding bicyclic products bearing at the bridgeheads of the embedded four‐membered ring aryl and ester moieties, respectively. This reaction is a rare example of a cycloaddition of two highly strained ring systems under Lewis acid catalysis. Mechanistic experiments provided insights into the reaction mechanism.