Hyperconjugative assistance in alkyne cyclizations and cycloadditions

在这个由化学系化学结构、动力学和机理计划支持的项目中，伊戈尔·阿拉布金教授和他的研究小组将把炔烃反应性的研究扩展到三个新的方向。它将使用计算来发现立体电子效应，能够控制炔烃的阴离子环化反应和非催化的炔环加成反应，并利用这一知识开发有效的化学过程。在这个项目的第一部分，研究小组将寻找两种几乎没有被探索过的炔环化模式：3-exo-dig和4-exo-dig闭合。拟议的实验将测试关于不同环化模式的相对效率的计算预测，并利用协作超共轭相互作用来控制反应性。在第二部分中，研究人员将使用负超共轭在竞争的内环化和外环化的微妙平衡对中实现选择性内切闭合。该项目的最后部分将测试超共轭辅助作为新的过渡态稳定方法在非催化的炔叠氮环加成反应中的应用。这项研究的智力价值在于通过实验和理论研究相结合的方式揭示了电子和结构因素对控制炔环化和环加成反应的效率和选择性的贡献。对轨道相互作用的关注将增加这些发现的一般重要性，拓宽我们对这些基本因素的理解，并导致自由基和阴离子反应新范式的发展。更广泛的影响将为炔烃反应在合成和材料科学中的成功应用奠定机理、结构和动力学基础。拟议的研究将加强我们对炔基和自由基物种的反应性的理解。计算与动力学研究的结合将用于验证有机反应研究的计算方法。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、研究生和博士后一级的研究人员提供一个将学习和发现结合起来的机会。这些成果将在出版物和外联活动中传播，包括参加本科生和研究生院的研讨会和讲座。

In this project supported by the Chemical Structure, Dynamics and Mechanisms Program of the Division of Chemistry, Professor Igor Alabugin and his research group will extend studies of alkyne reactivity into three new directions. It will use computations to discover stereoelectronic effects capable of controlling anionic cyclizations of alkynes and non-catalyzed alkyne cycloadditions and utilize this knowledge to develop efficient chemical processes. In the first part of this project, the research team will search for the two virtually unexplored alkyne cyclization patterns: 3-exo-dig and 4-exo-dig closures. Proposed experiments will test computational predictions regarding the relative efficiency of different cyclization patterns and utilize cooperative hyperconjugative interactions for the control of reactivity. In the second part, the researchers will use negative hyperconjugation to enable selective endo closures in the delicately poised pairs of competing endo and exo cyclizations. The final part of the project will test hyperconjugative assistance as the new transition state stabilization approach in non-catalyzed alkyne-azide cycloadditions. The intellectual merit of this research is in unraveling the contribution of electronic and structural factors controlling efficiency and selectivity of alkyne cyclizations and cycloaddtions through a combination of experimental and theoretical studies. The underlying focus on orbital interactions will increase the general importance of these findings, broaden our understanding of these fundamental factors and lead to the development of new paradigms of radical and anionic reactivity.The broader impact will be the laying of mechanistic, structural, and kinetic foundations for successful applications of reactions of alkynes in synthesis and materials science. The proposed research will enhance our understanding of the reactivity of the alkyne moiety as well as radical species. The combination of computations with kinetic studies will be used to validate computational approaches for studies of 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 publications and through outreach activities, including participation in symposia and lecturing at undergraduate and graduate institutions.