Trifluoroacetic acid has been discovered to be a highly effective and efficient reagent for the tandem Claisen rearrangement and cyclization reaction to yield 3-arylmethylene-3,4-dihydro-1 H-quinolin-2-ones from compounds obtained from the S N2 reaction between anilines and acetyl derivatives of Baylis–Hillman adducts of acrylates in the presence of DABCO. In contrast, similar compounds obtained from the acetyl derivatives of Baylis–Hillman adduct of acrylonitrile on treatment with trifluoroacetic acid directly furnish 3-arylmethyl-2-amino-quinoline via tandem Claisen rearrangement, cyclization and isomerization.