A scandium arylsulfonate-based coordination polymer as a heterogeneous catalyst for the friedel–crafts reaction of indoles with aldehydes

The scandium sulfonate-based coordination polymer Sc₂ (BPDS)₃, which is easily prepared by mixing scandium triisopropoxides and biphenyl-4,4’-disulfonic acid (BPDSA), is an air-stable and storable solid that effectively catalyzes the Friedel–Crafts reaction of indoles with aromatic aldehydes under heterogeneous conditions to afford various aryl(diindolyl)methanes. The catalyst can be reused without significant loss of activity after separation from the reaction mixture by simple centrifugation followed by drying.