Development of New Cascade Sequences for the Construction of Novel Chemical Structures

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The Organic Synthesis Program supports Professor Kung Wang's studies at the University of West Virginia of new cascade reaction sequences leading to the construction of novel chemical structures. Reaction sequences based on the cycloaromatization of enediynes and enyne-allenes, including (Z)-3-hexene-1,5-diynes and (Z)-1,2,4-heptatriene-6-ynes, lead to polycyclic carbon frameworks, while analogous cyclizations of enyne-ketenes, enyne-ketenimines, enyne-isocyanates, and enyne-carbodiimides afford access to novel polycyclic heterocycles. Cascade electrocyclizations of dienediynes provide reactive benzocyclobutadienes, the unusual polycyclic dimers of which represent synthetic entry to compounds containing multiple dibenzocyclooctatetraene units. Cyclizations of enediallenes lead to the formation of o-quinodimethanes and to the potential discovery of novel synthetic routes to estrone and tetracyclic structures forming the basis of a number of naturally-occurring diterpenes. Many of Nature's biologically active compounds display complex molecular structures, and the attempted synthesis of such compounds, whether for purposes of structure elucidation, large-scale production of scarce naturally occurring compounds, or preparation of next-generation synthetic analogs, requires the continuing development of new strategies to deal with their molecular complexity. By exploiting unusual cyclization reactions of electron-deficient precursor molecules, Professor Wang develops facile synthetic routes to a wide variety of polycyclic molecular structures containing all-carbon atoms as well as compounds containing nitrogen and oxygen atoms within their cyclic structures. These cyclization reactions are significant in their own right from a chemical perspective, addressing issues of fundamental importance with regards to organic structure and reactivity. Additionally, the reaction chemistry provides synthetic access to both recognized and novel chemical structures, affording new synthetic routes for the preparation of steroids such as estrone as well as other tetracyclic structures characteristic of a class of naturally-occurring compounds known as the diterpenes.