Metalloradical Catalysis for Selective Radical Reactions

在化学系化学催化项目的支持下，波士顿学院的Peter Zhang教授正在研究环境可持续的金属基催化工艺，以制备对科学和商业有用的有机化合物。大多数金属催化过程依赖于所谓的“极性反应”，其中化学反应一次涉及两个电子的变化。在新兴的“金属催化”概念的指导下，一次一个电子发生变化，张教授和他的同事团队正在开发利用自由基反应独特特征的新型催化系统。与通常需要稀有和昂贵的金属来介导双电子极性反应相比，我们感兴趣的单电子冶金反应是用基于地球上丰富和廉价的过渡金属（如钴）的催化剂进行的。因此，该资助的研究项目解决了精细化工生产中可持续性的重要问题，并为生物学、医学和材料带来了潜在的长期效益。资助项目的更广泛影响将扩展到在公众中推广科学，支持张氏团队为K-12教师提供教育资源，并开展外展活动，激发对STEM（科学，技术，工程和医学）的兴趣。作为这些努力的一部分，将创建并向公众提供题为“生命的色彩”的教育网络材料，并为高中学生和教师以及本科生提供在实验室获得第一手研究经验的机会。本项目的重点是建立金属催化作为控制自由基反应活性和立体选择性的一种全新的方法。基于手性卟啉钴（II）配合物的金属化学体系将被开发，以充分利用均溶自由基化学的潜力。这些新的催化自由基过程，既具有机械上的独特性，又具有操作上的简单性，将成为构建有机化合物的有价值的合成工具，包括生物学上重要的天然产物和药学上有趣的小分子。金属催化的概念旨在充分探索均解作为断键和成键的基本平台，它将对有机合成产生深远的影响，并有可能刺激基于自由基化学的进一步新的合成方法的发展。钴基金属自由基催化的进一步探索有可能指导基于开壳金属离子和手性配体的不同组合的新型金属催化剂体系的发展，这些体系可以催化广泛的立体选择性自由基反应。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 Peter Zhang of Boston College is studying metal-based catalytic processes for the environmentally sustainable preparation of organic compounds of utility to science and commerce. Most metal-catalyzed processes rely on so-called "polar reactivity" wherein chemical reactions involve changes of two electrons at a time. Guided by the emerging concept of "metalloradical catalysis" in which changes instead happen one electron at a time, Professor Zhang and his team of coworkers are developing new catalytic systems that take advantage of the unique features of radical reactions. In comparison with the typical need for rare and expensive metals to mediate two-electron polar reactions, the one electron metalloradical reactions of interest are carried out with catalysts based on earth-abundant and inexpensive transition metals such as cobalt. As such, the funded research project addresses important issues of sustainability in fine chemical manufacture and with potential long term benefits for biology, medicine, and materials. The broader impacts of the funded project extend to the promotion of science among the general public by supporting the Zhang group as they provide educational resources for K-12 teachers and stimulate interest in STEM (science, technology, engineering and medicine) conducting outreach activities. As part of these efforts, educational web-based material entitled "The Colors of Life" will be created and made available to the public, and opportunities will be provided for high school students and teachers, as well as undergraduate students, to gain first-hand research experiences in the laboratory.This project focuses on the establishment of metalloradical catalysis as a fundamentally new approach for controlling the reactivity and stereoselectivity of radical reactions. Metalloradical systems based on cobalt(II) complexes of chiral porphyrins will be developed to harness the full potential of homolytic radical chemistry. These new catalytic radical processes, which are both mechanistically distinctive and operationally straightforward, will serve as valuable synthetic tools for the construction of organic compounds, including biologically important natural products and pharmaceutically interesting small molecules. The concept of metalloradical catalysis, which aims at the full exploration of homolysis as a fundamental platform for bond-breaking and -making, will have a far-reaching impact on organic synthesis and it is likely to stimulate the development of further new synthetic methods based on radical chemistry. The further exploration of cobalt-based metalloradical catalysis has the potential to guide the development of new metalloradical catalyst systems based on different combinations of open-shell metal ions and chiral ligands that can catalyze a broad range of stereoselective radical reactions.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.