| The discovery of new activation modes is vital to the continuing importance of chemical synthesis to applications valued in medical and industrial settings. The use of small organic molecules as catalysts for important and new transformations in organic synthesis has come to the fore of academic chemical research since 2000. The MacMillan group has taken part in the discovery of new activation modes using imidazolidinone-based catalysts. Since 2007 we have been interested in expanding the scope of secondary amine catalysts toward single electron pathways that allow for the asymmetric formation of carbon-carbon bonds alpha to aldehydic carbonyls. SOMO (singly occupied molecular orbital) catalysis involves an umpolung coupling of an electrophilic enamine radical cation with nucleophilic silane partner, generating a new carbon-carbon bond (see Chapter 1). Chapter 2 introduces the application of this strategy toward ketones. Photoredox organocatalysis involves the coupling of enamine to fluorescent-light generated, stabilized alkyl radical, also furnishing new carbon-carbon bonds. Chapter 3 applies this mode of activation towards the cyano- and nitroalkylation of aldehydes and shows several applications. Chapters 4 and 5 introduce a new mode of activation, the organocatalytic conjugate addition of alkyl and aryl boranes to alpha,beta-unsaturated aldehydes, respectively. Chapters 2 and 3 espouse the importance of expanding a newly developed activation mode. Chapters 4 and 5 testify to the importance of discovering a new activation mode. |
