Trichloromethyl-substituted enones (1-aryl-4,4,4-trichlorobut-2-en-1-ones, ArCOCH=CHCCl 3, CCl 3-enones) undergo intramolecular transformation into 3-trichloromethylindan-1-ones (CCl 3-indanones) in Brønsted superacid CF 3SO 3H (triflic acid, TfOH) at 80 °C within 2-10 h in yields up to 92%. Protonation of the carbonyl oxygen of the starting CCl 3-enones by TfOH affords the key reactive intermediates, the O-protonated forms ArC(=OH +)CH=CHCCl 3, which are then cyclized into the target CCl 3-indanones. These cations have been studied experimentally by means of NMR spectroscopy in TfOH and theoretically by DFT calculations. Under the same superacidic conditions in TfOH, CCl 3-hydroxy ketones (1-aryl-4,4,4-trichloro-3-hydroxybutan-1-ones; ArCOCH 2CH(OH)CCl 3) undergo dehydration to the corresponding CCl 3-enones, which are further cyclized into CCl 3-indanones. The yields of CCl 3-indanones starting from CCl 3-hydroxy ketones are up to 86% in TfOH at 80 °C within 3-18 h.