Cobalt-Catalyzed Cycloadditions and Hydrofunctionalizations of Alkenes

Ohio State University, The, Columbus OH

Investigators

Abstract

With this award, the Chemical Catalysis Program of the NSF Division of Chemistry is supporting the research of Professor Thaliyil RajanBabu of The Ohio State University. Professor RajanBabu is developing efficient and selective reactions that can offer practical approaches to the synthesis of organic molecules for medicinal, agricultural, or material applications. In this context, new reactions involving the use of abundantly available and sustainable feedstock starting materials such as ethylene, butadiene, isoprene, methyl acrylate, earth-abundant metals such as cobalt and nickel, and ligands that bind to those metals are being examined. This research is solving two significant challenges in this area, namely, activation of stable molecules and their subsequent selective incorporation into other molecules. It is also providing outstanding opportunities for fundamental discoveries in chemistry. The interdisciplinary nature of this research, which covers the areas of organic, inorganic and organometallic chemistry, and employs the techniques from analytical, physical organic, and computational chemistry, also provides a useful platform for training undergraduate and graduate students. The RajanBabu group is involved in outreach activities with Columbus public schools, the Ohio Science Olympiad, and the REEL (Research Experiences to Enhance Learning) program at OSU. The later is transforming the undergraduate laboratory experience by incorporating state of the art instrumentation and providing experience on the use of this instrumentation to solve challenging chemical problems. Other outreach activities of Professor RajanBabu include giving lectures at universities including predominantly undergraduate institutions, industrial research centers, and conferences. 1,3-Dienes and enynes are classes of readily accessible substrates that have been used only rarely as precursors in intermolecular asymmetric C-C and C-G (G = a main group element) bond-forming reactions. The RajanBabu group recently reported the first examples of highly enantioselective cobalt(I)-catalyzed heterodimerization of a diene and an acrylate. A study of the reaction mechanism points to a new highly reactive low-valent cationic cobalt (I) species as a possible catalyst for this reaction. Preliminary results suggest that there are other reactions that could be catalyzed by a similar species. The RajanBabu group is developing these reactions, including asymmetric hydroboration, hydrosilylation, and hydroacylation. The proposed research is providing powerful tools for more efficient and selective synthesis of biologically relevant targets and their congeners, and adding to our repertoire of environmentally benign processes. At a fundamental level, the scope and limitations of these reactions and their mechanistic studies are revealing new ways of achieving chemo-, regio- and stereoselectivities of important organic reactions. The REEL program at OSU is introducing an advanced kinetic experiment using in situ IR spectroscopy to the undergraduate laboratory. The experiments are carefully chosen so that all students from a small class can collect data individually for a few minutes from an on-going reaction (borohydride reduction of a ketone, for example), and, do the kinetic analysis later, before submitting a full report for evaluation. This is introducing them to kinetics and spectroscopy, two topics in which few of our students currently get practical training in their regular laboratory classes, even though these topics are mainstays in both physical and organic chemistry. 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.