Mechanistic Role of Additives and Solvent in Sm(II)-Based Reactions

二碘化钐（SmI 2）和其他Sm（II）基还原剂为各种重要的合成转化提供了独特的试剂。 基于Sm（II）的还原剂的显着特征之一是，它们的反应性可以通过改变溶剂或添加助溶剂或其他添加剂来显着改变。 虽然在有机合成中使用Sm（II）试剂已经取得了很大的进步，但溶剂和添加剂在反应中的作用知之甚少，因此，这些还原剂-添加剂组合的全部潜力尚未实现。 本工作是针对理解溶剂和添加剂之间的关系和它们对Sm（II）介导的功能基团的转换率和选择性的影响，通过两个离散的mechanistic studies.The第一项研究将定义之间的关系的亲和性溶剂，质子供体，和协调或螯合添加剂的Sm（II）试剂和这些变量的关系Sm（II）的反应性。 这项工作将建立在何种程度上协调溶剂衰减Sm（II）的反应性，通过与基板和常用添加剂的相互作用，提供化学家与重要的机械数据比较Sm（II）-助溶剂配合物的反应性在一系列的溶剂中，它们是常用的。 总的来说，这部分工作的目标是通过将溶剂作为高摩尔浓度配体而不是固定介电常数的介质来处理分子水平上的溶剂化效应。 第二项研究解决了二碘化镍和其他过渡金属盐对Sm（II）介导的还原的机械功能。 催化二碘化镍和其他镍（II）盐的影响范围内的SmI 2的反应将严格审查通过一系列的机制研究采用停流分光光度法和反应量热法。 将使用反应进程动力学分析进一步研究为Ni（0）基化学提供证据的反应机理研究。随着这些研究的进行，将检查Ni（0）纳米颗粒的中间性以区分均匀性和基于胶体的化学。 这项工作的广泛目标是提供一个基于Sm（II）的化学机制的理解，可以外推和应用到一系列重要和有用的过程。 利用这种方法进行的研究可能会为科学界提供长期的利益，而不仅仅是演示单一的合成应用。 本提案中所包含的工作也将为研究生和本科生在有机合成中变得越来越重要的试剂的机械研究，使用和应用方面提供重要的专业准备。 学生将接受培训，使用和应用一系列有用的技术，而不是通常用于标准的有机实验室，因此，在这个项目中使用的工具的广度将提供独特的培训和有机学生的观点。 列入本科生从里海先进的实验室课程序列中的机械研究和发展的反应采用的SmI 2/催化二碘化镍系统将提供重要的培训，而不是典型的收购在传统的本科实验室课程。

Samarium diiodide (SmI2) and other Sm(II)-based reductants provide unique reagents for a variety of important synthetic transformations. One of the distinctive features of Sm(II)-based reductants is that their reactivity can be drastically altered by changing the solvent or by adding cosolvents or other additives. Although great strides have been achieved in the use of Sm(II) reagents in organic synthesis, the role of solvent and additives in reactions is poorly understood, and, as a result, the full potential of these reductant-additive combinations has not been realized. This work is directed towards understanding the relationship between solvent and additives and their effect on the rates and selectivities of Sm(II)-mediated functional group conversions through two discrete mechanistic studies.The first study will define the relationship between the affinity of solvents, proton donors, and coordinating or chelating additives for Sm(II) reagents and the relationship of these variables to the reactivity of Sm(II). This work will establish the degree to which coordinating solvents attenuate the reactivity of Sm(II) through interaction with substrates and commonly utilized additives providing chemists with important mechanistic data comparing the reactivity of Sm(II)-cosolvent complexes in a range of solvents in which they are commonly used. Overall, the goal of this portion of the work is to address the effects of solvation at the molecular level through the treatment of solvent as a high molarity ligand, not a medium of fixed dielectric constant. The second study addresses the mechanistic function of Ni diiodide and other transition metal salts on Sm(II)-mediated reductions. The impact of catalytic Ni diiodide and other Ni(II) salts on a range of reactions of SmI2 will be critically examined through a series of mechanistic studies employing stopped-flow spectrophotometry and reaction calorimetry. Mechanistic studies of reactions providing evidence for Ni(0)-based chemistry will be further investigated using reaction progress kinetic analysis. As these studies proceed, the intermediacy of Ni(0) nanoparticles will be examined to distinguish homogeneity from colloid-based chemistry. The broad goal of this work is designed to provide a mechanistic understanding of Sm(II)-based chemistry that can be extrapolated and applied to a range of important and useful processes. Studies utilizing this approach are likely to provide longer term benefits to the scientific community than simply the demonstration of a single synthetic application. The work contained in this proposal will also provide important professional preparation for graduate and undergraduate students in the mechanistic study, use, and applications of a reagent that is becoming increasingly important in organic synthesis. Students will receive training in the use and application of a range of useful techniques not typically used in standard organic laboratories and therefore the breadth of tools used in this project will provide unique training and perspective to organic students. Inclusion of undergraduate students from the Lehigh advanced laboratory course sequence in the mechanistic study and development of reactions employing the SmI2/catalytic Ni diiodide system will provide important training not typically acquired in a traditional undergraduate laboratory course.