Iminium Ion Catalysis: Chemical and theoretical tools to understand the catalytic cycle

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Metal free processes are increasingly used to develop novel, cleaner, more efficient and selective transformations in synthetic chemistry. Much recent interest has centred on iminium ion and enamine catalysis using cyclic secondary amines, which has been shown to be an effective platform a wide range of reactions, providing a wealth of new methods with which to perform standard synthetic protocols in high yield and enantiomeric excess. Despite impressive advances in recent years, however, a detailed understanding of the mechanisms for these reactions remains elusive and catalyst design remains essentially a hit-and-miss affair.We propose to address this fundamental lack of knowledge by carrying out a series of physical measurements of key quantities, such as rate constants and activation barriers, for individual steps involved in iminium ion catalysis, and ultimately to the entire catalytic cycle. Such measurements will be complemented by theoretical calculations of reaction mechanisms, already underway in our group. In this way, we will augment the existing high profile synthetic methodologies using this practically simple and mechanistically fascinating class of transformation, and ultimately facilitate rational design of new, more efficient catalysts.