CHAPTER 10: Trienamine-catalyzed Stereoselective Cycloadditions and Other Remote Functionalizations of Polyconjugated Enals/Enones

Organocatalyzed “catalysis-mediated with small organic molecule” stereoselective transformations have enjoyed tremendous growth in the last 17 years. Within this active area, amine-catalyzed activation of unmodified saturated and unsaturated carbonyl compounds through highest occupied molecular orbital (HOMO)-activating enamine and lowest unoccupied molecular orbital (LUMO)-activating iminium-ion formation have received cumulative attention. Particularly, the HOMO-raising activation strategy has been applied to the maximum number of asymmetric transformations via enamine, dienamine, trienamine and singly occupied molecular orbital (SOMO)-activation strategies. Recently, trienamine catalysis, an extension of the vinylogous enamine concept, has demonstrated the unique ability to promote stereoselective remote ε-position functionalizations for polyenals/polyenones. The successful realization of excellent diastereo- and enantio-selectivity in the reaction product by employing either a bulky, steric, shielding aminocatalyst or a bifunctional aminocatalyst, even though the ε-site of the reaction is seven bonds away from the stereodifferentiating element of the catalyst, validates the great usefulness of this activation strategy in synthetic organic chemistry. In this chapter, we will discuss the initial encounter and regular developments in the area of asymmetric trienamine catalysis over the past few years.