Sc(OTf)(3)-Catalyzed Bicyclization of o-Alkynylanilines with Aldehydes: Ring-Fused 1,2-Dihydroquinolines

A Sc(OTf)(3)-catalyzed cascade Prins-type cyclization reaction of o-alkynylanilines, bearing a hydroxy or amine functionality, with aldehydes affords 1,2-dihydroquinoline derivatives having an extra fused ring efficiently under mild reaction conditions. It is interesting to observe the reversed reactivity in the highly selective formation of 1,2-dihydroquinoline derivatives instead of the formation of the usually favored indole derivatives.