Synthesis of allenyl carbonyls and their use as heterodienes in a novel inverse electron demand hetero-Diels-Alder reaction

We report the development of a novel hetero-Diels-Alder reaction involving the use of allenyl carbonyls as heterodienes. We have described the synthesis of a variety of allenyl carbonyls via a base promoted and manganese mediated isomerization of alkynyl carbonyls for use in methodology studies. In our model studies, a variety of enamines were utilized effectively as dienophiles to form "hydrolyzed" Diels-Alder adducts while investigating optimal reaction conditions. Initial studies towards the synthesis of an allenyl ester tethered to an aldehyde for an eventual application in an intramolecular Diels-Alder reaction were performed. Possible mechanisms were proposed while computational studies were performed in attempt to rationalize product selectivity.