Electrophilic substitution of indoles catalyzed by triphenyl phosphonium perchlorate: Synthesis of 3-acetyl indoles and bis-indolylmethane derivatives

Triphenyl phosphonium perchlorate (TPP) is found to catalyze the acetylation of indoles with acetic anhydride to give 3-acetyl indoles. Similarly bis-indolylmethane derivatives were prepared by the electrophilic substitution reaction of indole with substituted benzaldehydes.