Designer Silver Catalysts for Tunable C-H and C=C Bond Amination
One of the major challenges facing chemists in the 21st century is identifying cheap and sustainable ways to transform substances obtained from petroleum and biorenewable sources into useful building blocks for the synthesis of critically needed pharmaceuticals, agrochemicals, polymers, and fuels. The carbon-hydrogen single bond (C-H) and carbon-carbon double bond (C=C) are two of the most common chemical bonds in organic compounds and represent convenient locations to introduce new functionality into those compounds. However, it is difficult to achieve a desired reaction at only one specific C-H or C=C bond of the many that are present in a single molecule. In this project, Dr. Schomaker is developing new silver catalysts that transform these bonds to important and useful carbon-nitrogen bonds with high yields, less waste, and with the ability to selectively make many different useful products from a single starting compound. Studies to understand the unique features of silver that enable such high, predictable levels of control over this reactivity are key to designing improved and durable catalysts that efficiently transform precious hydrocarbon feedstocks into valuable materials, even using water as reaction solvent. Dr. Schomaker is active in outreach programs related to her research interests in catalysis to educate and engage the general public, especially young women, in fields related to science, technology, engineering and mathematics (STEM). Her activities include developing hands-on experimental modules centered on topics related to silver catalysis for "Expanding Your Horizons", a STEM-centered program for girls in 6-8th grades, as well as entertaining and educational demonstrations on silver chemistry for "Science is Fun" public presentations.
With funding from the Chemical Catalysis Program of the Chemistry Division, Dr. Jennifer Schomaker of the University of Wisconsin is developing low-cost, modular catalysts for the tunable functionalization of C-H bonds to valuable C-N bonds. Such methods are crucial for streamlined syntheses of pharmaceuticals, agrochemicals, chiral ligands and amine building blocks, but represent a long-standing challenge in the field of catalysis. To address this issue, Dr. Schomaker is pursuing a fundamental understanding of the unique features of silver complexes that enable them to achieve catalyst-controlled transformations of C-H bonds to C-N bonds through metal-catalyzed nitrene transfer processes. A combination of variable temperature (VT) NMR, diffusion spectroscopy, mechanistic and computational studies (density functional theory and higher-level ab initio methods such as CASSCF) are being employed to assess how the features of N-donor ligands influence the electronic structure of the metal nitrene, the dynamic/fluxional behavior of reactive intermediates in solution and promotion of non-covalent interactions between substrate/catalyst to influence the site of the C-H functionalization event. Ultimately, this work is establishing universal design principles for the synthesis of catalysts that facilitate non-directed C-H functionalizations capable of overriding innate reactivity preferences that are extendable to other metals and other C-H oxidation reactions, particularly in an asymmetric context. Dr. Schomaker is also active in a number of STEM outreach programs to engage and educate students in her community about the importance of catalysis in solving challenges that currently face our society. She is particularly interested in increasing the representation of women in STEM disciplines to support the broader impacts of this work.
