Photoinduced Intramolecular Addition of 3-Acyl-2-haloindoles to Alkenes

1,2-Fused indoles and pyrroles were prepared via an efficient intramolecular photoaddition reaction of 1-(ω-alkenyl)-2-haloindole-3-carbaldehydes and 1-(ω-alkenyl)-2-chloropyrrole-3-carbaldehydes. The presence of an acyl group was necessary for the photocyclization reactions. The halogen-atom-retained exo- and endo-cyclization products were generally produced with results similar to those of an atom-transfer cyclization reaction. In contrast, unsaturated cyclization products were obtained in the photoreaction of substrates having methyl groups on the vinyl group.