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

在化学系化学合成项目和促进竞争性研究的既定项目（EPSCoR）的支持下，爱荷华大学的Scott Daly和高尔盖特大学的Jason Keith将研究金属配合物，这种配合物能够在一锅反应中实现目标有机化合物的连续、多步骤分子组装。要探索的创新概念是开发活性硼分子，它可以结合金属，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，将简单的化学构建块转化为用于制药、农用化学品和其他精细化学品的复杂分子支架。这项研究也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。“化学排”是爱荷华大学备受赞誉的外展项目，旨在帮助退伍军人和军事附属机构学习化学入门课程。“化学排”的持续发展，以及高露洁大学（Colgate University）密集的本科生研究工作，将促进非传统和高风险STEM（科学、技术、工程和数学）专业学生的招聘和支持。串联反应是耦合催化反应，通过两个或两个以上机械上不同的过程依次转化底物。当需要两种或两种以上的催化剂时，这些反应往往受到共催化剂不相容性的限制，并且难以将反应性推广到广泛类别的重要化学转化中。有人提出，这些问题可以通过含有活性硼配体的单一多功能金属配合物来解决，这些配合物能够与金属进行串联催化反应。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同步加速器光谱测量（b和P k边缘XANES （x射线吸收近边缘光谱））来补充，以绘制反应机制和控制理想反应性的潜在电子结构变化。这些合作努力有望阐明产生理想的串联金属配体催化的化学因素，并为现有方法提供一种可能的替代方法。预计这些研究将与主基团化学和催化具有交叉相关性，同时也为其他类型的催化反应提供新的结构-反应性见解。该奖项反映了美国国家科学基金会的法定使命，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.