Complexity Control in Enyne Photocycloadditions

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With this award, the Chemical Synthesis Program of the Chemistry Division is funding Professor Scott Sieburth of the Department of Chemistry at Temple University to study a photochemical cycloaddition reaction between aromatic rings and enynes (a.k.a. vinyl acetylenes) and application of the products. Cycloaddition reactions are among the most powerful ways of building molecules. This new cycloaddition assembles an eight-membered ring, a medium ring that is not easily accessible, by bringing together two four-atom components. The [4+4] class of cycloadditions is itself unusual and use of enynes for this reaction is unprecedented. The product contains a strained and highly reactive allene that undergoes subsequent chemistry, including rearrangements and additional cycloaddition reactions. Overall, this photoreaction takes simple components and builds complex products in a single step that are rich in functional groups and stereochemistry. With a goal of building useful new chemical structures rapidly, trapping of the reactive allene functional group will be studied, both inter- and intramolecularly. The broader impacts involve training undergraduate students, graduate students and postdoctoral researchers. This work could lead to new chemical structures with useful properties, structures that are not accessible using standard synthetic transformations. Moreover, the use of light to induce reactions, instead of chemical reagents, is an intrinsically "green" process. Successful development of this chemistry will have a broad impact on research that relies on novel molecules and their properties, such as the pharmaceutical and agricultural industries. In addition, this project will provide training in both modern organic synthesis and photochemistry for students, from undergraduate to post-doctoral, including those from groups historically underrepresented in the sciences.