CAREER: Nucleophilic Cobalt Photocatalysis for the Generation of Radicals from Non-Traditional Precursors

职业：亲核钴光催化从非传统前体产生自由基

• 批准号: 2338732
• 负责人: Spencer Pitre
• 金额: $ 68万
• 依托单位: Oklahoma State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-07-01 至 2029-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2338732&HistoricalAwards=false
• 关键词: CAREER; Nucleophilic; Cobalt; Photocatalysis; Generation

With the support of the Chemical Catalysis Program in the Division of Chemistry and the Established Program to Stimulate Competitive Research (EPSCoR), Spencer Pitre of Oklahoma State University is developing cobalt catalysts to generate carbon radicals from non-traditional precursors using visible light irradiation. Carbon radicals have become an indispensable tool for the construction of complex organic molecules. However, most organic compounds must be preactivated to be effective as radical precursors, adding undesired synthetic steps and creating additional byproducts and chemical waste. Inspired by Vitamin B12 and its natural reactivity, Dr. Pitre and his research group are leveraging analogous cobalt complexes to generate carbon radicals from new classes of precursors, avoiding the need for preactivated substrates. These methods rely on visible light photochemistry to mediate radical formation, an emerging synthetic strategy that enables mild reaction conditions. Despite its importance to the field of organic chemistry, students at the undergraduate level do not receive any exposure to photochemistry in the traditional curriculum. This omission is being addressed through an annual undergraduate photochemistry workshop, which gives students that have limited access to research opportunities from across Oklahoma the chance to learn about photochemistry and its impact on the development of new chemistries. These research effort will also serve to train a diverse group of graduate and undergraduate researchers in photochemistry and catalysis.Cobaloximes, which mimic the reactivity of the cobalt atom of Vitamin B12, are among the strongest nucleophiles known when in the Co(I) oxidation state and can undergo SN2 reactions with electrophiles. The resulting alkyl–cobalt can undergo facile homolytic cleavage when irradiated with visible light to generate carbon-centered radicals. Despite having similar nucleophilicities, cobaloximes are generally less efficient than Vitamin B12 at catalyzing radical generation from electrophilic substrates. Dr. Pitre and his research team are probing the effect of the axial ligands on each step of the catalytic cycle to develop more efficient nucleophilic cobalt photocatalysts. These nucleophilic cobalt photocatalysts are being tuned to enable radical formation from new classes of precursors, including chloroform, electron-deficient alkenes, iminium ions and vinyl halides and triflates. If successful, these studies will expand understanding of cobaloxime chemistry and enhance the potential for the development and deployment of Co(I) cobaloxime catalytic systems.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.

在化学系化学催化项目和刺激竞争研究既定项目 (EPSCoR) 的支持下，俄克拉荷马州立大学的 Spencer Pitre 正在开发钴催化剂，利用可见光照射碳从非传统前体产生碳自由基。自由基已成为构建复杂有机分子不可或缺的工具，然而，大多数有机化合物必须预先活化才能有效地作为自由基前体，从而增加了不需要的合成。受维生素 B12 及其天然反应性的启发，Pitre 博士和他的研究小组正在利用类似的钴络合物从新型前体中产生碳自由基，从而避免了对预活化底物的需要。可见光光化学介导自由基形成，这是一种新兴的合成策略，可以实现温和的反应条件，尽管它对有机化学领域很重要，但本科生并没有接触过任何光化学。传统课程中的这一遗漏正在通过一年一度的本科生光化学研讨会得到解决，该研讨会为来自俄克拉荷马州各地的研究机会有限的学生提供了了解光化学及其对新化学发展的影响的机会。旨在培养光化学和催化领域的各类研究生和本科生研究人员。钴肟模仿维生素 B12 钴原子的反应性，是已知的最强的亲核试剂之一。 Co(I) 氧化态，可与亲电子试剂发生 SN2 反应，在可见光照射下，生成的烷基钴可发生容易的均裂，生成以碳为中心的自由基，尽管钴肟具有相似的亲核性，但其效率通常低于维生素 B12。 Pitre 博士和他的研究小组正在探索轴向配体对每个亲电子底物催化自由基生成的影响。催化循环的一步是开发更有效的亲核钴光催化剂，这些亲核钴光催化剂可以通过新型前体形成自由基，包括氯仿、缺电子烯烃、亚胺离子以及卤化乙烯和三氟甲磺酸酯。研究将扩大对钴肟化学的理解，并增强钴肟催化材料的开发和应用潜力该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。