Mechanistic Studies Directed Toward Universal Ligands and Catalytic Reactions of Samarium Diiodide

化学结构、动力学和机理B项目支持理哈伊大学Robert A. Flowers教授对二碘化钐（SmI2）的化学机理进行研究。SmI2是一种重要的有机合成试剂，因为它在有机合成中可以介导许多重要的反应，包括还原、还原偶联和级联反应。SmI2的一个重要特点是可以通过添加助溶剂或添加剂来控制反应的化学选择性和非对映选择性。这项工作有两个科学目标。第一个目标是开展机制研究，确定溶剂、质子供体和配位或螯合添加剂对Sm（II）试剂的亲和力的影响。这些变量与Sm（II）的反应性之间的关系将应用于sm2使用容易获得、廉价和无毒的添加剂还原官能团的替代方法的开发。这项工作的第二个目标将集中在机制研究上，旨在检查已知的基于sm2的催化系统，并利用从这些研究中收集的信息来帮助开发使用sm2和其他基于Sm（II）的还原剂的催化反应。许多通过电子转移进行的有机反应的高度复杂性是基于我们对阴离子、阳离子、自由基和相关自由基离子的机理理解。化学家通过使用金属基氧化剂和还原剂来相互转化这些中间体的能力，导致了在成键事件中利用一种或多种活性中间体来合成具有重要社会意义的复杂分子的反应的发展。目前应用最广泛的单电子还原剂是SmI2，但添加剂在这些反应中的作用尚不清楚。在本项目框架内进行的实验旨在提供对Sm（II）基化学的机理理解和添加剂的作用，这些添加剂可以推断并应用于一系列重要和有用的过程，包括催化反应的发展。利用这种以机制为中心的方法进行研究，可能比展示单一的综合应用为科学界带来长期的好处。

The Chemical Structure, Dynamics and Mechanisms B Program supports Professor Robert A. Flowers of Lehigh University to carry out mechanistic studies on the chemistry of samarium diiodide (SmI2). SmI2 is an important reagent in organic synthesis due to its versatility in mediating numerous, fundamentally important reactions in organic synthesis including reductions, reductive couplings, and cascade reactions. One of the important features of SmI2 is that the addition of cosolvents or additives can be used to control the chemo- and diastereoselectivity of reactions. There are two scientific objectives of this work. The first objective is to carry out mechanistic studies that define the impact of the affinity of solvents, proton donors, and coordinating or chelating additives for Sm(II) reagents. The relationship between these variables and the reactivity of Sm(II) will be applied to the development of alternative approaches for the reduction of functional groups by SmI2 using readily available, inexpensive, and non-toxic additives. The second objective of this work will focus on mechanistic studies designed to examine known SmI2-based catalytic systems and employ the information gleaned from these studies to aid in the development of catalytic reactions employing SmI2 and other Sm(II)-based reductants.The high degree of sophistication of many organic reactions that proceed through the transfer of electrons is based on our mechanistic understanding of anions, cations, radicals, and related radical ions. The ability of chemists to interconvert these intermediates through the use of metal-based oxidants and reductants has led to the development of reactions that utilize one or more reactive intermediates in bond-forming events to synthesize complex molecules of great societal importance. The most widely used single electron reductant is SmI2, but the roles of additives in these reactions are not well understood. The experiments carried out within the framework of this project are designed to provide a mechanistic understanding of Sm(II)-based chemistry and the role of additives that can be extrapolated and applied to a range of important and useful processes including the development of catalytic reactions. Studies utilizing this mechanism-centered approach are likely to provide longer-term benefits to the scientific community than the demonstration of a single synthetic application.