An unexpected Sc(OTf)3-catalyzed and air-mediated cascade reaction of o-aminoacetophenones with methanamines was discovered as an efficient synthetic approach to a novel class of fluorescent fused-four-ring dibenzo[b,h][1,6]naphthyridine derivatives. Two possible mechanisms of the reaction were proposed. The photophysical properties of the dibenzo[b,h][1,6]naphthyridine were initially considered.