Professor Chae S. Yi of Marquette University is supported by the Chemical Catalysis Program in the Division of Chemistry to investigate the synthetic and mechanistic aspects of transition metal-catalyzed C-H bond activation reactions. Multinuclear ruthenium-hydride catalysts will be synthesized and used to achieve this objective. Another objective of the proposed research is to design and use chiral ruthenium-oxazoline catalysts for the asymmetric C-H bond oxidation reactions.
Catalytic C-H bond oxidation reactions are extensively used for the industrial production of oxygenated compounds from ubiquitous hydrocarbon compounds. The proposed research will contribute to our knowledge in homogenous catalysis, and will advance the development of energy efficient and environmentally compatible catalysts for important industrial processes. Students at Marquette University will be trained in organometallic chemistry and homogeneous catalysis and will be exposed to an international exchange experience in chemical catalysis. Minority students from Alcorn State University and the local community colleges in Milwaukee will be involved in this research.
for the NSF grant (CHE-1011891). The central theme of the proposed research has been to develop and utilize novel catalytic methods for sustainable synthesis of a variety of complex organic molecules of pharmaceutical importance under environmentally benign conditions. This report summarizes the major research outcomes resulted from the group’s projects. Major Outcome #1: Green Catalytic C–H Coupling Methods for Alkenes and Arenes. Facing with growing environmental pollutions from petrochemical consumptions, one of the most urgent challenges in catalysis research centers on the development of new green catalytic processes that give desired products without forming wasteful byproducts. During the current NSF project period, we have been able to develop novel catalytic C–H coupling methods for arene and alkene substrates, which are suitable for the synthesis of a variety of high-value target molecules without forming any toxic byproducts. We have successfully used the catalytic method to directly functionalize a number of steroid molecules such as cholesterol and progesterone, as well as for a number of privileged natural products such as strychnine, quinine and sinomenine (a morphine analog) to efficiently form the coupling products. The catalytic method exhibits enzyme-like specificity in forming these alkylation products, and provides an effective protocol for synthesizing a library of pharmaceutically important compounds without resorting to multistep synthetic manipulations. The transformative features of the catalytic method are that it employs readily available alkene, phenol and alcohol substrates, exhibits a broad range of substrate scope while tolerating a variety of heteroatom functional groups, and liberates water as the only byproduct. We recently published three articles including one in Science journal on the basis of these results. Major Outcome #2: Catalytic Coupling Reactions of Biobased Reagents via Unreactive C–N and C–O Bond Cleavage. The group’s another major effort has been centered on the development of green catalytic coupling methods for harnessing bio-derived substrates. Catalytic reforming processes for biomass feedstock such as amino acids, carbohydrates and celluloid materials have tremendous potentials in transforming industrial processes for biofuels and bio-based commodities, which can significantly alleviate the dependence on petroleum based feedstock. We have been able to design a highly selective catalytic deaminative and decarboxylative coupling method of natural a-amino acids by using a well-defined cationic ruthenium-hydride catalyst. The most salient feature of the catalytic coupling method is that the direct C–C and C–N bond cleavage reaction of biomass-derived amino acid substrates without using any reactive reagents or forming harmful byproducts. We have successfully demonstrated a broad range of substrate scope and chemoselectivity for the alkylation reaction. We have also been able to develop a highly selective catalytic method for unsymmetrical ethers from the direct dehydration of two different alcohols. The catalytic method tolerates a range of sensitive functional groups, does not generate any wasteful byproducts, and most significantly, exhibits high selectivity toward the formation of unsymmetrically substituted ethers. In short, we have successfully developed a number of ecologically sustainable catalytic methods that utilize bio-based amino acids and alcohols for the synthesis of complex organic molecules of biological importance. Broader Impacts to Society. The group’s research has transpired a number of significant discoveries in the field of green catalysis, particularly in the development of energy-efficient and environmentally sustainable catalytic coupling methods. These developed catalytic methods provide a new platform for efficient synthesis of pharmaceutical agents and bioactive products. During the project period, the PI’s research program offered graduate education and training in organometallic chemistry and homogeneous catalysis for the workers. The PI’s group has also hosted the summer intern research program for two undergraduate chemistry students including an African American woman student. These individuals will contribute to highly skilled chemical workforce in the U.S. upon completion of their training.
