Proton-coupled electron-transfer in Sm(II)-proton donor reactions

美国国家科学基金会化学部的化学结构、动力学和机理项目支持里海大学化学系Robert Flowers教授的研究。弗劳尔斯教授和他的学生正在研究碘化钐（SmI2）的反应机制，这是一种广泛用于有机合成的试剂。该项目的第一个目标是检查质子供体（醇和水）对反应活性和效率的作用，并确定电子和质子是按顺序转移的，还是该过程是协调一致的，并通过正式的氢原子转移发生。该项目的第二个目标是利用smi2 -质子供体系统研究的机制信息来开发催化反应。本科生和研究生接受一系列科学技术方面的培训。向小学生伸出援手会导致与当地社区的持续接触。最后，在这些研究过程中制定的实验方案的视频记录在Flowers研究小组的网页上自由传播，以帮助使用基于SmI2的试剂的科学家。SmI2是通过单电子转移来还原底物和活性中间体的最广泛使用的试剂之一。虽然SmI2的大多数反应都需要质子供体，但这种试剂组合的机制尚不完全清楚，目前的观点是还原和还原偶联反应是通过连续的电子转移、质子转移过程进行的。这项工作测试了还原和还原偶联反应通过正式的氢原子转移进行的假设，并且电子和质子的耦合转移负责Sm(II)-配位质子供体还原底物的独特反应性，这些底物通常难以通过单电子转移还原。随着对Sm(II)-质子供体系统的机理研究的开展，从这些研究中获得的数据用于开发有用的和用户友好的催化反应；这是该领域长期存在但难以实现的目标。整合了一系列实验技术以及质子耦合、电子转移在合成中的应用，为学生提供了一个动态的智力环境。该教育计划包括与当地小学的长期合作，旨在培养人们对科学的更大兴趣。最后，当研究发表在同行评议的期刊上时，所有实验协议的视频记录都被制作出来，以帮助那些想要重复反应协议的科学家。

The Chemical Structure, Dynamics, and Mechanism Program of the NSF Chemistry Division supports the research of Professor Robert Flowers in the Department of Chemistry at Lehigh University. Professor Flowers and his students are examining the mechanism for reactions of samarium (II) iodide (SmI2), a widely used reagent in organic synthesis. The first goal of this project is designed to examine the role of proton donors (alcohols and water) on the reactivity and efficiency of reactions and determine whether electrons and protons are transferred in sequential steps, or whether the process is concerted and occurs through a formal hydrogen atom transfer. The second goal of this project is to use the mechanistic information from studies on SmI2-proton donor systems to develop catalytic reactions. Students at the undergraduate and graduate level receive training in a range of scientific techniques. Outreach to elementary students leads to sustained engagement with the local community. Finally, video recordings of experimental protocols developed during these studies are freely disseminated on the Flowers research group webpage to assist scientists who use reagents based on SmI2. SmI2 is among the most widely employed reagents that reduce substrates and reactive intermediates through single electron transfer. Although most reactions of SmI2 require proton donors, the mechanism of this reagent combination is not fully understood and the current view is that reductions and reductive coupling reactions proceed through a sequential electron-transfer, proton-transfer processes. This work tests the hypothesis that reductions and reductive coupling reactions proceed through a formal hydrogen atom transfer and that the coupled transfer of an electron and proton is responsible for the unique reactivity of Sm(II)-coordinating proton donor reductions of substrates which are typically recalcitrant to reduction through single electron transfer. As mechanistic work on Sm(II)-proton donors systems is performed, data obtained from these studies is used for the development of useful and user-friendly catalytic reactions; a longstanding, but elusive goal in this field. Integration of a range of experimental techniques along with synthetic applications of proton-coupled, electron-transfer in synthesis provides a dynamic intellectual environment for students at all levels of study. The educational plan includes long-term engagement with local elementary schools designed to nurture greater interest in science. Finally, as research is published in peer-reviewed journals, video recordings of all experimental protocols are made to aid scientists who want to repeat the reaction protocols.