The title compound, the 4-phenyl-6-(trifluoromethyl)-3,4-dihydroquinolin-2(1 H )-one ( 4 ) with chemical formula: (C 16 H 12 F 3 NO), was synthesized from N -[4-(trifluoromethyl)phenyl]cinnamamide ( 3 ), chemical formula: (C 16 H 12 F 3 NO), through an intramolecular cyclization mediated by triflic acid. Preliminary molecular characterization of both compounds was performed by Fourier transform infrared spectroscopy, gas chromatography mass spectrometry, and nuclear magnetic resonance spectroscopy ( 1 H, 13 C); crystallographic characterization was completed by X-ray diffraction of polycrystalline samples. The title compound 4 crystallized in a monoclinic system and unit-cell parameters are reported [ a = 16.002 (3), b = 5.170 (1), c = 17.733 (3) Å, β = 111.11 (2)°, unit-cell volume V = 1368.5 (3) Å 3 , Z = 4] P 2 1 / c (No. 14) space group; the title compound 3 crystallized in a monoclinic system and unit-cell parameters are reported [ a = 12.902 (2), b = 5.144 (1), c = 20.513 (5) Å, β = 91.67 (2)°, unit-cell volume V = 1360.7 (4) Å 3 , Z = 4] P 2 1 / c (No. 14) space group.