A Dehydro-Diels-Alder Reaction

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With this award, the Chemical Synthesis program is supporting Professor Kay M. Brummond at the University of Pittsburgh to develop the intramolecular didehydrogenative-Diels-Alder (IMDDA) reaction to prepare naphthalene derivatives and benzo-fused heterocycles. These substances are valuable building blocks for a variety of applications but are not readily available through known synthetic methods. The operational simplicity and scalability of the IMDDA has the potential to facilitate preparation of previously inaccessible aromatic compounds with the potential for application to organic light emitting diodes, liquid crystals, imaging agents, chiral ligands, and pharmaceuticals. Sustainable and green alternatives for the preparation of styrenyl compounds as IMDDA precursors will be explored. The thermal removal of hydrogen gas from IMDDA adducts to form aromatic compounds offers an environmentally benign alternative to reagent-based oxidation protocols. This research will provide state of the art training in synthetic organic chemistry for graduate students on a project with significant potential scientific broader impacts. In the IMDDA, [2+4] cycloaddition of tethered styrenyl and alkynyl groups is followed by thermal loss of molecular hydrogen to provide a naphthalene derivative. This research is expected to significantly expand the scope and utility of the IMDDA, making this reaction a viable avenue for the preparation of functionalized naphthalenes, dihydronaphthalenes and benzofused heterocycles. In addition, IMDDA reaction conditions will be developed to control the diverging reaction pathways for the selective and predictable formation of either an aromatic or a dihydroaromatic product. Through mechanistic studies, a better understanding of the acceptorless dehydrogenation reaction will be developed, and computational insight will be applied to guide the selection of reaction conditions, substrates and targets. Finally, it is expected that these thermal reaction conditions will be compatible with a variety of functionality, and thus amenable to the preparation of highly substituted and diversely functionalized naphthalenes and other valuable aromatic compounds.