Metalloradical Catalysis for Selective Radical Reactions

Boston College, Chestnut Hill MA

Investigators

Abstract

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.