In the presence of trifluoromethanesulphonic (triflic) acid, isobutyronitrile reacts with anisole, 1,3-dimethoxybenzene, resorcinol, 1,3,5-trimethoxybenzene, and phloroglucinol at room temperature to give acylation products. A study of the reactions of acetonitrile and isobutyronitrile with triflic acid has shown that these modified Houben–Hoesch reactions occur by initial cyclotrimerization of the nitriles to 1,3,5-triazinium triflate salts followed by a slow reaction of the salts with the aromatic substrate. Support for this comes from the isolation of 2-(4-methoxyphenyl)-2,4,6-tri-isopropyl-1,2-dihydro-1,3,5-triazine from the reaction between anisole, triflic acid, and isobutyronitrile. Similar 1,2-dihydro-s-triazines and their salts have been prepared by reaction of trimethyl-s-triazinium triflate with 1,3-(MeO)2C6H4, and tri-isopropyl-s-triazinium triflate with 1,3-(RO)2C6H4(R = H or Me) and 1,3,5-(MeO)3C6H3; these salts are easily hydrolyzed to the corresponding aromatic ketones. The salt [1,3,5-Me3C3N3H2]+ 2Ō3SCF3 also reacts with o-phenylenediamine to give 2-methylbenzimidazolinium triflate in 83% yield. Nitrilium salts [RCNMe]+Ō3SCF3(R = Me, Ph, or PhCH2) undergo rapid reactions with 1,3-(MeO)2C6H4 to form acylation products after hydrolysis, and N,N-dimethylaniline similarly affords 4-Me2NC6H4COMe on reaction with [MeCNMe]+Ō3SCF3 at room temperature.