Catalytic Asymmetric Five-Component Tandem Reaction: Diastereo- and Enantioselective Synthesis of Densely Functionalized Tetrahydropyridines with Biological Importance

The first catalytic asymmetric five-component tandem reactions of -keto esters, aromatic aldehydes and anilines have been established in the presence of a chiral phosphoric acid, affording densely functionalized tetrahydropyridines with concomitant generation of five sigma bonds and two stereogenic centers in high diastereo- and enantioselectivities (up to >99:1 dr, 95:5 er). In addition, the first isolation and preparation of a diene species as the key intermediate of the reaction has been successfully realized, leading to the formation of the desired tetrahydropyridine via further condensation with in situ generated imine, which supported the proposed tandem [4+2] reaction pathway to some extent. This protocol not only represents the first enantioselective example of this five-component tandem reaction, but also provides an unprecedented access to enantioenriched tetrahydropyridines with structural diversity, which holds great potential in medicinal chemistry.