Lanthanide(III)-catalyzed multi-component aza-Diels–Alder reaction of aliphatic N-arylaldimines with cyclopentadiene

The Ln(OTf)3-catalyzed formal aza-Diels–Alder (or Povarov) reaction of cyclopentadiene with in situ generated N-arylimines containing enolizable protons is described. This three-component Povarov reaction generates highly functionalized C-2 aliphatic substituted tetrahydroquinolines, heterocycles that were previously inaccessible using the Povarov reaction, because of the instability of the intermediate aliphatic N-arylaldimine.