Indolecarbonyl coupling reactions promoted by samarium diiodide: application to the synthesis of indole-fused compounds

Hydroxyalkylations of indole-3-carbonyls were performed through the help of an N-sulfonyl group or a cyano group at the C-2 position by the promotion of samarium diiodide. The indolecarbonyl coupling reactions occurred in high stereoselectivity through chelate transition states. Intramolecular indolecarbonyl couplings of 1-(3-oxopropyl)indole-3-carboxaldehydes were accomplished as the indolecarbonyl group was more reactive to SmI2 than the aliphatic carbonyl group.