2,4,6-Triphenylpyrylium tetrafluoroborate is used as a sensitizer to carry out the photo oxidation of cathecol. It is also used in the preparation of three N-alkylpyridinium photosensitizers by reacting with (1R,2S)-(-)-norephedrine, (S)-(+)-2-(aminomethyl)pyrrolidine and (R)-(-)-1-cyclohexylethylamine.