Bifunctional Catalysts for MHAT Hydrofunctionalization of Alkenes

在化学系化学催化项目的支持下，斯克里普斯研究所的Ryan Shenvi教授将研究一种新型的贱金属催化。生产商业产品和实验性新材料的化学反应会造成沉重的经济和环境负担。当这些反应由少量贵金属（如铂、金、铱）催化时，这些负担就可以减轻。然而，获取和移除这些贵金属可能会产生自己的环境、经济和政治问题。本研究寻求用铁等富土金属催化剂代替贵金属催化剂。通过这项工作，旧的化学反应和现有的材料可以产生更少的负面影响。此外，这些催化剂使贵金属无法获得的新化学反应和新材料成为可能。通过这些努力，各种各样的研究生将被训练成进入科技行业的劳动力。神威集团计划在社区学校开展化学推广活动，以吸引下一代科技专业人士。烯烃交叉偶联通常涉及贵金属配合物，它们经历连续的双电子内球反应。这些途径包括底物的顺序激活，其中金属中心与中间体共价结合：氧化加成、配位、迁移插入、β-氢化物消除、解复合。这些步骤都可以限制底物的范围，特别是烯烃配位步骤，由于空间排斥力，其速率随着烯烃取代的增加而降低。一个较少研究的烯烃反应途径涉及金属氢化物氢原子转移（MHAT），质子耦合电子转移（PCET）的一个子集。这个外球基本步骤直接从烯烃生成以碳为中心的自由基，而不需要氧化还原活性助剂或三烷基锡氢化物。与内球、配位金属氢化物反应随着烯烃取代的增加而减慢相反，MHAT反应可以在四取代烯烃上或在空间拥挤中高速率发生，甚至在叔胺和生物分子（如DNA）之间的稀水缓冲液中也可以发生。该研究将研究和扩展一类新型的基于mhat的烯烃功能化反应，其中贱金属催化剂在每个烯烃碳上催化成键，而不需要任何中间金属-碳键的形成。反应中间体化学、复杂分子合成和配体设计交叉的问题将通过这项工作得到解决。新的生物活性材料、化学反应和催化剂的见解有望从这项催化研究中产生。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 Catalysis program in the Division of Chemistry, Professor Ryan Shenvi of Scripps Research will study a new type of base metal catalysis. Chemical reactions that produce commercial products and experimental new materials can create a heavy economic and environmental burden. When these reactions are catalyzed by small quantities of precious metals (e.g. platinum, gold, iridium), these burdens can be lessened. However, obtaining and removing these precious metals can create their own environmental, economic and political problems. This research seeks to replace precious metal catalysts with earth abundant metal catalysts such as iron. Through this work, old chemical reactions and existing materials can be made with fewer negative impacts. In addition, these catalysts enable new chemical reactions and novel materials that are unavailable to precious metals. Through these efforts, a diverse body of graduate students will be trained to enter the science and technology workforce. Chemical outreach activities from the Shenvi group to community schools are planned to engage the next generation of science and technical professionals.Alkene cross-coupling traditionally involves precious metal complexes that undergo sequential two- electron, inner-sphere reactions. These pathways involve sequential activations of substrate in which the metal center bonds covalently to intermediates: oxidative addition, coordination, migratory insertion, β- hydride elimination, decomplexation. Each of these steps can restrict the substrate scope, especially the alkene coordination step, whose rate decreases with increased alkene substitution due to steric repulsion. A lesser studied alkene reaction pathway involves metal hydride hydrogen atom transfer (MHAT), a subset of proton-coupled electron transfer (PCET). This outer-sphere elementary step generates a carbon- centered radical directly from an alkene without the need for redox-active auxiliaries or trialkyltin hydrides. In contrast to inner-sphere, coordinative metal-hydride reactions that decelerate with increasing alkene substitution, MHAT reactions can occur at high rates on tetrasubstituted alkenes or amidst steric crowding, even in dilute aqueous buffer among tertiary amines and biomolecules like DNA. The proposed research will study and expand a novel class of MHAT-based alkene functionalization reactions in which a base metal catalyst mediates bond formation at each olefinic carbon without any intermediate metal-carbon bond formation. Problems at the intersection of reactive intermediate chemistry, complex molecule synthesis and ligand design will be addressed through this work. New bioactive materials, chemical reactions and catalyst insights are expected to result from this research into catalysis.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.