New Catalysts for Cis-Selective Metathesis: Agostic Interaction and Meso-N-Heterocyclic Carbenes

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This project will synthesize new catalysts for cis-selectivity in olefin metathesis. Two new, unexplored approaches will be taken in this project: (1) Use of agostic interactions in early transition metal Fischer carbene complexes to guide selectivity in enyne cross metathesis. In particular, we intend to improve the catalyst stability building upon what we have learned previously in the Diver group while studying enyne metathesis. (2) Building on N-heterocyclic carbene design we will construct an aromatic 'wall' on one side of meso-N-heterocyclic carbenes to control catalyst selectivity in ruthenium carbenes. Currently, the olefin metathesis provides one of the most effective methods for catalytic carbon-carbon double bond construction, and has been widely used by chemists in many fields. Despite the huge success of metathesis chemistry, the major limitation is control of double bond geometry: cis-double bonds cannot be made selectively. This project is focused on this cis-selectivity problem through catalyst development.With this award, the Organic and Macromolecular Chemistry Program is supporting the research of Professor Steven T. Diver of the Department of Chemistry at the State University of New York-Buffalo. Professor Steven Diver's research efforts center on the development of new metathesis methods for the synthesis of rings, the study of the catalytic mechanism of enyne metathesis and the development of new carbene catalysts. This three-pronged effort has impacted our understanding of fundamental aspects of metal carbene reactivity and led to improvements in selectivity in certain synthetic applications. Development of new carbene catalysts is expected to enhance cis-selectivity and lead to a better understanding of which factors are critical to selectivity. Metathesis methods are highly efficient, using small amounts of ruthenium carbene catalysts (known as the Grubbs carbenes) and are widely applicable to the synthesis of small molecules (such as pharmaceuticals) and polymeric structures (such as nanomaterials). Successful development of new catalysts will have an impact on synthesis in the pharmaceutical sector, leading to improved efficiency in drug production.