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.

在化学催化计划的化学和启用竞争研究的既定计划（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，以使用可见光光照射从非传统前体产生碳自由基。碳自由基已成为建造复杂有机分子的必不可少的工具。但是，大多数有机化合物必须被预选为有效作为根部的先驱物，从而添加未卫生的合成步骤并创建其他副产品和化学废物。受维生素B12及其自然反应性的启发，Pitre博士及其研究小组正在利用类似的钴络合物来产生新的前体类别的碳自由基，从而避免了对预催化的底物的需求。这些方法依靠可见光光化学来介导自由基的形成，这是一种新兴的合成策略，可实现轻度的反应条件。尽管对有机化学领域的重要性很重要，但本科级别的学生在传统课程中没有获得任何光化学的接触。通过年度本科光化学研讨会来解决这一遗漏，该研讨会使俄克拉荷马州各地研究机会的学生有机会了解光化学及其对新化学发展的影响的机会。这些研究工作还将有助于培训一群在光化学和催化领域的研究生和本科研究人员。核钙蛋白脂肪素（模仿维生素B12的钴原子的反应性）是在CO（i）氧化状态中所知道的强大核致毒液，并且可以在氧化状态下进行SN2反应与电动机的反应。当用可见光照射以产生以碳为中心的自由基时，所得的烷基 - 库库可以进行齐全的均质裂解。尽管具有相似的核植物能力，但在催化自由基底物的催化自由基产生时，cobaloxime的效率通常低于维生素B12。 Pitre博士和他的研究团队正在探测轴向配体对催化循环每个步骤的影响，以开发出更有效的核纤维卵形钴光催化剂。这些核植物钴光催化剂正在调节，以使新的前体的自由基形成，包括氯仿，电子缺陷烷烯，易胺离子和乙烯基卤化物和triflates。如果成功的话，这些研究将扩大对co氧化化学的理解，并增强CO（i）co（i）co（i）钴氧化催化系统的发展和部署的潜力。该奖项反映了NSF的法定任务，并被认为是通过基金会的智力优点和更广泛的影响标准通过评估来评估的支持。