Synthesis of Ligand-Centered Boron Cations to Access Tandem Reactions with Transition Metals

在化学系化学合成项目和刺激竞争性研究既定项目（EPSCoR）的支持下，爱荷华州大学的Scott Daly和高露洁大学的Jason基思将研究金属络合物，这种络合物能够在一锅反应中实现目标有机化合物的串联、多步分子组装。待探索的创新概念是开发活性硼分子，其结合金属并允许使用单一金属催化剂进行两种不同的催化反应。 这一策略有望建立更有效和更具成本效益的方法，将简单的化学结构单元转化为用于药物，农用化学品和其他精细化学品的复杂分子支架。这项研究还将为来自不同背景的研究生和本科生提供重要的劳动力发展和科学培训。招募和支持非传统和有风险的STEM（科学，技术，工程和数学）专业将通过化学排的持续发展得到促进，化学排是爱荷华州大学一个广受好评的外联项目，旨在帮助退伍军人和军事附属机构学习化学入门课程，串联反应是一种耦合的催化反应，通过化学反应将底物依次转化为两个或多个不同的机械过程。当需要两种或更多种催化剂时，这些反应通常受到助催化剂不相容性的限制，以及难以概括广泛类别的重要化学转化的反应性。有人提出，这些问题可以解决使用单一的多功能金属络合物含有活性硼配体能够进行催化反应，在串联的金属。使用环加成催化作为工具，Daly团队将评估硼配体的化学变化如何影响立体选择性和反应产率，不同反应条件下的催化稳定性以及金属的串联交叉偶联范围。合成工作将由基思研究小组的密度泛函理论计算和尖端的同步加速器光谱测量-B和P K边XANES（X射线吸收近边光谱）-来补充，以绘制出控制理想反应性的反应机制和潜在的电子结构变化。这些合作努力有望阐明产生所需的串联金属配体催化的化学因素，并提供了一种可能的替代方法。预计这些研究将与主族化学和催化具有交叉相关性，同时也提供与其他类型催化反应密切相关的新结构-反应性见解。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With the support of the Chemical Synthesis program in the Division of Chemistry and the Established Program to Stimulate Competitive Research (EPSCoR), Scott Daly of the University of Iowa and Jason Keith of Colgate University will study metal complexes that enable tandem, multistep molecular assembly of targeted organic compounds in one-pot reactions. The innovative concept to be explored is the development of reactive boron molecules that bind metals and allow two different catalytic reactions to be performed using a single metal catalyst. This strategy holds promise for establishing more efficient and cost-effective methods to transform simple chemical building blocks into complex molecular scaffolds used in pharmaceuticals, agrochemicals, and other fine chemicals. This research will also provide important workforce development and scientific training for graduate and undergraduate students from diverse backgrounds. The recruitment and support of nontraditional and at-risk STEM (science, technology, engineering and mathematics) majors will be facilitated by continued development of the Chemistry Platoon, an acclaimed outreach project at the University of Iowa aimed at assisting veterans and Military affiliates in introductory chemistry courses, and by intensive undergraduate research efforts at Colgate University.Tandem reactions are coupled catalytic reactions that sequentially transform a substrate via two or more mechanistically distinct processes. These reactions are often limited by co-catalyst incompatibility when two or more catalysts are required, as well as difficulties generalizing the reactivity for broad classes of important chemical transformations. It is proposed that these problems can be addressed using single multifunctional metal complexes containing reactive boron ligands capable of performing catalytic reactions in tandem with the metal. Using cycloaddition catalysis as a tool, the Daly team will assess how chemical changes at the boron ligand affect stereoselectivity and reaction yields, catalytic stability under different reaction conditions, and tandem cross-coupling scope at the metal. Synthetic efforts will be complemented by density functional theory calculations by the Keith research team and by cutting-edge synchrotron spectroscopy measurements-B and P K-edge XANES (X-ray absorption near edge spectroscopy)-to map out reaction mechanisms and underlying electronic structure variations that govern desirable reactivity. These collaborative efforts are expected to illuminate chemical factors that yield desirable tandem metal-ligand catalysis, and provides a possible alternative to established methods. These studies are anticipated to have cross-cutting relevance to main-group chemistry and catalysis while also affording new structure-reactivity insights germane to other types of catalytic reactions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.