4-Indolylbutanals from rhodium-catalyzed hydroformylation of allylindoles as precursors of benzofused indolizines

New 4-indolylbutanals have been prepared via a rhodium-catalyzed hydroformylation of differently substituted N-allylindoles. The aldehydes bearing an electron-donating group on the indole nucleus 3-position can evolve into benzofused indolizines via a one pot intramolecular cyclodehydration.