Metalloradical Catalysis for Stereoselective Carbene and Nitrene Transfers

美国国家科学基金会化学部化学催化项目的X教授获得了这个奖项。南佛罗里达大学的Peter Zhang将开发金属自由基催化，并将寻求立体选择性自由基反应的应用。金属自由基催化代表了一种控制C-和N-中心自由基反应的反应性和选择性的全新方法。稳定的金属自由基如钴（II）卟啉络合物能够活化重氮试剂和有机叠氮化物以分别干净地产生C-和N-中心的自由基，其中氮以受控和催化的方式作为唯一的副产物。最初形成的C-和N-中心的自由基，这仍然与钴（II）卟啉络合物络合，并被称为钴-卡宾和-氮烯自由基，分别可以进行常见的自由基反应，如自由基加成和原子抽象，但有效地控制卟啉配体环境的反应性和立体选择性。包括Co-C/Co-N键的低的和适当的键离解能的几个因素是成功的基于Co（II）的催化卡宾和氮烯转移的关键。通过卟啉配体的可调的电子，空间和手性环境的支持，这种一般概念的钴（II）基金属自由基催化将被应用于各种自由基过程的发展，包括一些立体选择性的卡宾和氮烯transfer.The概念的金属自由基催化可能会有深远的影响，在几个领域的研究，包括卡宾，氮烯和自由基化学。它的建立将促进金属自由基催化剂体系的进一步发展，该体系具有开壳金属离子和手性配体的不同组合，用于各种立体选择性自由基反应，与离子反应相比具有许多固有的合成优势。由于金属自由基催化可以催化生成自由基中间体，而不需要化学计量的引发剂，如常用的有机锡试剂，它也将具有积极的环境影响。卟啉配体的生物学和医学相关性，以及手性化合物作为药物，香料和芳香化学品，农业化学品和特种材料的实际应用，将使计划中的研究成为一个很好的主题，以促进公众之间的科学，为K-12教师提供教育资源，并激发K-12学生的科学兴趣。

With this award from the Chemical Catalysis Program in the Chemistry Division at the National Science Foundation Professor X. Peter Zhang of the University of South Florida will develop metalloradical catalysis and will seek applications for stereoselective radical reactions. Metalloradical catalysis represents a fundamentally new approach for controlling reactivity and selectivity of radical reactions of both C- and N-centered radicals. Stable metalloradicals such as cobalt(II) porphyrin complexes are capable of activating diazo reagents and organic azides to cleanly generate C- and N-centered radicals, respectively, with nitrogen as the only byproduct in a controlled and catalytic manner. The initially formed C- and N-centered radicals, which remain complexed with cobalt(II) porphyrin complexes and are termed as cobalt-carbene and -nitrene radicals, respectively, can undergo common radical reactions such as radical addition and atom abstraction, but with effective control of reactivity and stereoselectivity by the porphyrin ligand environment. Several factors including the low and appropriate bond dissociation energy of Co-C/Co-N bonds are key for the successful turnover of the Co(II)-based catalytic carbene and nitrene transfers. Through the support of porphyrin ligands with tunable electronic, steric, and chiral environments, this general concept of Co(II)-based metalloradical catalysis will be applied for the development of various radical processes, including a number of stereoselective carbene and nitrene transfers.The concept of metalloradical catalysis may have a far-reaching impact in several areas of research, including carbene, nitrene and radical chemistry. Its establishment will stimulate further development of metalloradical catalyst systems with different combinations of open-shell metal ions and chiral ligands for various stereoselective radical reactions, which have a number of inherent synthetic advantages in comparison with ionic reactions. Since metalloradical catalysis can generate radical intermediates catalytically without the need of stoichiometric initiators such as the commonly employed organotin reagents, it will have a positive environmental impact as well. The biological and medical relevance of porphyrin ligands, together with the well demonstrated practical applications of chiral compounds as pharmaceuticals, flavor and aroma chemicals, agricultural chemicals, and specialty materials, will make the planned study an excellent theme to promote science among the general public, to provide education resources for K-12 teachers, and to stimulate scientific interests of K-12 students.