The asymmetric Povarov reaction with α‐alkyl styrenes as dienophiles was catalyzed by an N,N′‐dioxide L4–Sc(OTf)3 complex. Enantiopure tetrahydroquinoline derivatives with a quaternary stereocenter at the C4 position were synthesized for the first time. A wide variety of α‐alkyl styrenes and N‐aryl aldimines were tolerated in the reaction, to give excellent diastereo‐ (up to 99:1 d.r.) and enantioselectivities