Chemoselective synthesis of bis(indolyl)methanes using sulfonic acid-functionalized chitosan

Herein, we describe the electrophilic substitution reaction of indole with aldehydes and ketone using sulphonic acid functional group containing chitosan for the synthesis of bis(indolyl)methanes. The reaction is chemoselective affording a product from aldehydes and indole. The catalyst can be reused up to three times without great loss in yields. Hence, chitosan–SO 3 H (CTSA) proved to be a heterogeneous, efficient, chemoselective, and reusable catalyst for the synthesis of bis(indolyl)methane derivatives. Graphic abstract