CAS: Catalytic Synthesis via Small Molecule Evolution

在化学系化学合成计划的支持下，堪萨斯大学的Jon Tunge教授正在研究开发利用分子中固有能量的策略，以实现高效和环境可持续的化学制造过程。具体地说，从简单的原料中释放出稳定的小分子(二氧化碳和/或氢)，有时与收集光能相结合，将提供推动化学反应的能量，而不需要传统的、更浪费的能量输入方法。为了进一步减轻化学反应对环境的影响，同时允许开发新型反应途径，将使用基于钴的催化剂作为关键促进剂，钴是一种富含稀土的金属，而不是传统的更昂贵和稀有的贵金属。预计所开发的方法将适用于各种材料的合成，这些材料具有潜在的应用，如药剂、农用化学品和其他对科学、工程和商业有价值的物质。这个资助项目的更广泛的影响延伸到了为社会带来的好处，因为Tunge教授和他的同事们参与了旨在将这项研究的目标与培训和招聘计划相结合的外展和教育活动，这些培训和招聘计划包含了促进绿色化学原则的内容。这些活动的一个重要目标是吸引来自不同背景的学生，包括在科学、技术、工程和数学(STEM)领域中代表性较低的群体的个人，以应对可持续化学的当代挑战。资助的项目侧重于通过C-C和C-H键的断裂催化生成活性中间体的化学转化的发展。正在开发的催化途径利用脱羧化为直接从廉价的羧酸原位生成合成有用的活性中间体提供了一种有效的策略。其他正在研究的工艺利用析氢反应(HER)实现原子经济官能化。钴催化剂在脱羧基偶联反应中取代了传统的昂贵的钯催化剂，预计将允许新的转化类型，而这些类型是目前技术无法实现的。此外，光氧化还原催化的放氢将允许氨基酸和多肽的特定部位功能化，同时也使区域受控的脱羧基Heck样酰化成为可能。这些研究将为合成化学家提供一个通用的范例，用于在温和的条件下访问活性物种，同时产生最少的废物：(1)用于过渡金属催化剂氧化还原洗牌的可见光光氧化还原催化剂，以及(2)通过释放最小分子氢进行氧化偶联的放氢。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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 Synthesis Program in the Division of Chemistry, Professor Jon Tunge of the University of Kansas is studying the development of strategies that harness the inherent energy in molecules to enable efficient and environmentally sustainable processes for chemical manufacturing. Specifically, the release of small stable molecules (carbon dioxide and/or hydrogen) from simple feedstocks, sometimes in combination with harvesting light energy, will provide the energy to drive chemical reactions without the need for traditional, more wasteful, methods of energy input. To further lessen the environmental impact of the chemistry while also allowing for the exploitation of new types of reaction pathways, catalysts based on cobalt, an earth abundant metal, rather than traditional more expensive and rare precious metals, will be employed as critical promoters. It is anticipated that the methods developed will be applicable to the synthesis of a wide variety of materials with potential applications as pharmaceutical agents, agrochemicals, and other substances of value to science, engineering, and commerce. The broader impacts of the funded project extend to the benefits accrued to society as Professor Tunge and his coworkers engage in outreach and educational activities designed to integrate the goals of this research with training and recruitment programs that incorporate the promotion of 'green chemistry' principles. A significant goal of these activities will be to attract students from diverse backgrounds, including individuals belonging to groups underrepresented in science, technology, engineering, and mathematics (STEM) fields, to address contemporary challenges in sustainable chemistry.The funded project is focused on the development of chemical transformations based on the catalytic generation of reactive intermediates via the cleavage of C–C and C–H bonds. The catalytic pathways being developed utilize decarboxylation to provide an efficient strategy for the in situ formation of synthetically useful reactive intermediates directly from inexpensive carboxylic acids. Other processes under investigation utilize the hydrogen evolution reaction (HER) for atom-economical functionalization. Cobalt catalysts replace traditional, expensive, palladium catalysts in decarboxylative coupling reactions and are anticipated to allow for new transformation types that are inaccessible using current technologies. Additionally, photoredox-catalyzed hydrogen evolution will allow for the site-specific functionalization of amino acids and peptides, while also enabling regiocontrolled decarboxylative Heck-like acylations. These studies will advance a general paradigm for synthetic chemists to use for accessing reactive species under mild conditions, while generating minimal waste using: (1) visible light photoredox catalysts for redox shuffling of transition metal catalysts, and (2) hydrogen evolution to allow oxidative couplings through liberation of the smallest molecule, hydrogen.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.