Combining stereoelectronics, traceless directing groups and dynamic covalent chemistry for the design of alkyne cascades: towards carbon-rich molecules and materials

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In this project funded by the Chemical Structure, Dynamic & Mechanism B and the Macromolecular, Supramolecular and Nanochemistry Programs of the Chemistry Division, Professor Igor Alabugin of the Department of Chemistry and Biochemistry at Florida State University will develop new routes to conjugated carbon nanostructures with predesigned shape and functionality based on atom-economical transformations of high-energy alkyne precursors into conjugated cyclic structures. Such transformations will be useful in organic synthesis and materials science. In particular, this work will pave the way to carbon-rich conjugated molecules that can serve as unique components in the design of optoelectronic materials, energy storage devices, sensors, transistors, solar cells, and polymer composites. This research will also broaden the mechanistic, structural, and kinetic foundations for design of new organic reactions. The theoretical and experimental components of this work will allow training of specialists in each area and will provide researchers at the undergraduate, graduate and postdoctoral levels with an opportunity to integrate learning and discovery. The results will be disseminated in peer-reviewed publications and outreach activities, including participation in symposia and lecturing at undergraduate and graduate institutions. In this project, ortho polyyne chains of varying sizes, equipped with different functionalities, are built in a modular fashion using well-characterized and reliable cross-coupling chemistry. In the key step, these systems are then "zipped" up via a cascade of fast and selective radical cyclizations. Selectivity of initial radical attack on the multifunctional substrates is controlled by the presence of "traceless directing groups" that are removed in the course of the one-pot process. In parallel, self-terminating reactions of enynes overcome stereoelectronic restrictions on the 6-endo-dig cyclizations by utilizing alkenes as synthetic equivalents of alkynes with the final "oxidation" accomplished in the cascade termination step as an aromatizing C-C bond scission.