β‐N‐Heterocyclic Cyclobutane Carboximides: Synthesis through a Tandem Base‐Catalyzed Amidation/aza‐Michael Addition Protocol and Facile Transformations

A stereoselective one‐pot double derivatization of cyclobutene‐1‐carboxylic acid via a mild organic base catalyzed amidation/aza‐Michael addition of benzo[d]oxazol‐2(3H)‐ones has been developed. This unprecedented tandem reaction provides access to novel β‐N‐heterocyclic cyclobutane carboximide derivatives with a trans geometry. The carboximide moiety reacts smoothly with nucleophiles, allowing access to diverse derivatives of trans‐β‐N‐heterocyclic cyclobutanecarboxylic acid, including peptidomimetic structures. A stereoselective one‐pot double derivatization of cyclobutene‐1‐carboxylic acid via a mild organic base catalyzed amidation/aza‐Michael addition of benzo[d]oxazol‐2(3H)‐ones has been developed.