In this project funded by the Chemical Structure, Dynamics and Mechanisms B Program of the Chemistry Division, Professor Ross A. Widenhoefer in the Department of Chemistry at Duke University investigates the mechanisms of gold-catalyzed chemical reactions, especially those in which a divalent carbon atom is transferred to a carbon-carbon double bond to form a cyclopropane. This is a synthetic transformation of growing importance. Studies include experiments to determine the scope and mechanisms of gold-catalyzed processes and the structure of gold complexes. This research provides mechanistic insight that will serve the ever growing global community of researchers working toward the development of new and more efficient gold(I) catalyzed transformations. Research activities are fully integrated into the scientific education and training of graduate and undergraduate student researchers, including students from groups traditionally underrepresented in the sciences. Graduate students augment their research experience through participation in educational activities offered through the Duke University Graduate School. Graduate students also participate in community outreach activities in collaboration with Dr. Ben Bobay of the Duke Nuclear Magnetic Resonance (NMR) center which provide local high school students with hands-on exposure to modern high-field NMR spectroscopy and one-on-one instruction in the processing and interpretation of NMR data.
This project investigates the structure and reactivity of gold carbenoid complexes and cationic gold carbene complexes, including those relevant to gold-to-alkene carbene transfer (cyclopropanation), gold alpha-oxo carbene and carbenoid complexes, and cationic beta, gamma-unsaturated gold carbene complexes. Despite a growing body of work in this area, limited experimental information is available regarding mechanisms which involve these gold complexes. Research activities fill important gaps in this field and develop an experimentally-grounded understanding of the nature of the complexes generated either through carbene transfer from stabilized diazo compounds or through the oxidation of alkenes in the presence of gold. The research addresses three main areas of inquiry: (1) elucidation of the mechanisms of gold to alkene carbene transfer by modeling the transition state for carbene transfer, independent synthesis of gold metallacyclobutane complexes, and kinetic analysis of gold to alkene carbene transfer under stoichiometric conditions; (2) evaluation of the nature and reactivity of cationic gold alpha-oxo carbene and carbenoid complexes by studying the reactions of gold complexes with stabilized N- and S-ylides and the reactions of pyridine N-oxides and with cationic gold complexes; and (3) interrogation of the structure and reactivity of unsaturated gold carbene complexes through the synthesis and characterization of cationic gold allenylidene and vinyl carbene complexes.
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.
