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

佛罗里达州立大学化学与生物化学系的Igor Alabugin教授将在高能炔前体向共轭环结构的原子经济转化的基础上，开发具有预先设计形状和功能的共轭碳纳米结构的新途径，该项目由化学结构、动力学与机理B以及化学系的大分子、超分子和纳米化学项目资助。这种转化将在有机合成和材料科学中发挥作用。特别是，这项工作将为富碳共轭分子铺平道路，这些分子可以作为光电材料、储能设备、传感器、晶体管、太阳能电池和聚合物复合材料设计中的独特组件。这项研究也将为设计新的有机反应拓宽机理、结构和动力学基础。这项工作的理论和实验部分将允许培训每个领域的专家，并将为本科生，研究生和博士后水平的研究人员提供整合学习和发现的机会。研究结果将在同行评议的出版物和外联活动中传播，包括参加专题讨论会和在本科和研究生机构演讲。在这个项目中，不同尺寸的邻位聚烯烃链，配备不同的功能，以模块化的方式使用良好表征和可靠的交叉偶联化学构建。在关键的一步中，这些系统通过一系列快速和选择性的自由基环化被“压缩”起来。对多功能底物的初始自由基攻击的选择性是由“无迹导向基团”的存在控制的，这些基团在一锅过程中被去除。与此同时，炔的自终止反应通过利用烯烃作为炔的合成等价物，克服了对6端环化的立体电子限制，最终的“氧化”在级联终止步骤中作为芳构化C-C键的断裂完成。

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.