Project Summary: This proposal outlines the vision of a systematic, ongoing effort directed towards the fundamental understanding of catalytic asymmetric reactions and its application to the development of more selective catalysts and discovery of novel concepts in asymmetric organocatalysis. Our research program, since its inception in September 2013, has accumulated a vast body of mechanistic information including experimental kinetic isotope effect (KIE) studies and transition state analysis of several important organocatalytic reactions with a special emphasis on proline-enamine catalysis. This proposal describes our current efforts in utilizing this information to design more selective catalysts and to develop novel concepts in enamine catalysis. These efforts have met with some initial success and we have successfully developed a general strategy to obtain synthetically useful enantiodivergence – access to both antipodes of a target molecule using the same enantiomer of chiral catalyst – in proline-enamine catalysis. In this proposal, we are extending the application of this concept to develop two novel concepts in proline-enamine catalysis – chemodivergent and diastereodivergent enamine catalysis. The latter concept, diastereodivergent catalysis, provides access to complementary diastereomers of a chiral molecule in high enantiopurity using the same chiral catalyst – a phenomenon that has no precedent in asymmetric catalysis. Finally, we are seeking to expand the physical organic toolkit available to the synthetic organic community by developing probes for the rapid elucidation of reaction mechanisms. We have developed a novel methodology – intramolecular designed reactant (IDR) – for the rapid determination of 13C KIEs at natural abundance. We propose to apply the IDR method to conduct a high-throughput mechanistic study of several palladium catalyzed cross-coupling reactions. Cross-coupling reactions are the most-utilized carbon-carbon bond-forming strategy in medicinal chemistry and the mechanistic information gleaned from this study is expected to have a significant impact on process development in the pharmaceutical industry.