Professor Eric J. Enholm, of the Department of Chemistry at the University of Florida, is supported by the Organic Synthesis Program for his studies of new reactions and methodology using radical anions. These studies focus on metal- and silicon-associated ketyl radical anions, representing bifunctional intermediates with both free radical (single electron) and anionic/nucleophilic (two electron) behavior. Professor Enholm exploits the reactivity of these intermediates to develop novel allylation, ring scission, radical trapping, alkylation, and sigmatropic rearrangement chemistry. Reactions of allylstannanes with allylic O-stannyl ketyls represents a mild and chemically neutral alternative to classic Michael-type additions of organometallic reagents. Silane-based analogues of these reactions promise both to provide environmentally benign alternatives to tin reagents and to allow access to asymmetric reactions through the use of optically active O-silyl ketyls. Tin(IV) enolates undergo (3,3)-sigmatropic shifts via formation of intermediate allylic O-stannyl ketyls, offering entry to the ABC ring system of phyllanthocin, a novel bisabolene glycosidic inhibitor of several cancer tumor cell lines. Carbometallation reactions mediated by tin(IV) enolates permit the formation of products similar to those obtained via Conia ene reactions but at greatly reduced temperatures. With the support of the Organic Synthesis Program, Professor Eric J. Enholm, of the Department of Chemistry at the University of Florida, explores and exploits new reactions of radical anions, a class of reactive compounds which contain both a negatively-charged site and a site bearing a single unpaired electron. By taking advantage of the reactivity of each of these sites, Professor Enholm is able to prepare a wide variety of carbon `skeletons` which can serve as intermediate scaffolds for the construction of various natural products, medicinal agents, and biologically active molecules. His studies also target the development of silicon-based alternatives to the more traditional tin-based reagents for the formation of organic radicals, offering promise for the development of environmentally friendly alternatives to the toxic tin reagents.
