Solid-Phase Synthesis of 2,3,5-Trisubstituted Indoles

2,3,5-Trisubstituted indoles are synthesized in three steps starting from resin-bound aniline 2. R1 is introduced by a palladium-mediated coupling of the aryl iodide with terminal alkynes followed by intramolecular cyclization to form the indole core. Acylation at C-3 with an acid chloride in the presence of AlCl(3) catalyst introduces R2. The indole C-5 position is then diversified either by Sonagashira or Suzuki couplings with the aryl bromide. Finally, indole N-1 can be modified by post-cleavage methylation. [reaction: see text]