TANDEM EPOXIDE-OLEFIN CYCLIZATION-PINACOL REARRANGEMENT

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This proposal outlines the development of a tandem epoxide-olefin cyclization-pinacol rearrangement. This reaction will convert monocyclic alkanes bearing trimethylsilyloxy, alkenyl, and epoxy substituents into cis-bicyclic alkanones by the action of a Lewis acid. A variety of cycloalkane ring sizes, alkenyl substituents, and epoxides will be incorporated into the reaction substrates, and the effects that each of these variables has on the facility, stereoselectivity, and regioselectivity of the reaction will be noted. For example, incorporating cation-stabilizing functionality at the terminus of the epoxide should cause the mode of cyclization to switch from exo to endo. Another variation of the reaction that will be explored is the use of a vinylsilane as the alkenyl substituent. This would result in the presence of a carbon-silicon bond in the reaction product, which can be oxidized to an alcohol. Collectively, these studies will provide an effective method of predictably generating a wide variety of highly substituted bicyclic products. As several of these products are likely to either have biological activity or be intermediates leading to biologically significant compounds, this process will doubtless find wide application in medicinal research. The utility of the tandem epoxide-olefin cyclization- pinacol rearrangement is demonstrated in a proposed total synthesis of the modified labdane diterpenoid cluytene D, a natural product which has never been synthesized in the laboratory.