Enantioselective Organocatalytic Four‐Atom Ring Expansion of Cyclobutanones: Synthesis of Benzazocinones

Abstract

AbstractAn enantioselective Michael addition– four‐atom ring expansion cascade reaction involving cyclobutanones activated by a N‐aryl secondary amide group and ortho‐amino nitrostyrenes has been developed for the preparation of functionalized eight‐membered benzolactams using bifunctional aminocatalysts. Taking advantage of the secondary amide activating group, the eight‐membered cyclic products could be further rearranged into their six‐membered isomers having a glutarimide core under base catalysis conditions without erosion of optical purity, featuring an overall ring expansion– ring contraction strategy.