Triphenylphosphine-m-sulfonate/Carbon Tetrabromide as an Efficient and Easily Recoverable Catalyst System for Friedel-Crafts Alkylation of Indoles with Carbonyl Compounds or Acetals

A solid complex, conveniently prepared from commercially available sodium triphenylphosphine-m-sulfonate (TPPMS) and carbon tetrabromide, can be used as an easily recoverable and reusable catalyst system for Friedel-Crafts alkylation of indoles with carbonyl compounds or acetals to produce bis(indolyl)alkane products (BIAs).