Trifluoromethanesulfonic acid supported on carbon used as catalysts in the synthesis of flavones and chromones

Solid acid catalysts based on trifluoromethanesulfonic acid (TFMS) were synthesized using two different activated carbons as supports. They were characterized by FT-IR, DTA–TGA and BET, and their acidity was measured by potentiometric titration with n-butylamine. The new catalysts were checked for the cyclization of 1-(2-hydroxyphenyl)-3-phenyl-1,3-propanedione. The reaction experiments were performed using toluene as the solvent, at reflux. In all cases the product (flavone) was obtained with high selectivity. Conversions up to 84% were obtained using the supported catalyst TFMSC2. The activity of the catalysts is strongly dependent on the textural properties of the support used to obtain them, particularly their mean pore size. Optimal reaction conditions were applied to the preparation of seven substituted flavones and chromones.