β-(3-Iodopropoxy)-substituted α,β-unsaturated lactams, lactones, and cycloalkenones (eight examples) underwent reductive radical reactions in a dichloromethane solution of N,N-diisopropylethylamine (Hünig's base) upon irradiation with visible light (λ=419 nm). Apart from plain reduction reactions (hydro-de-iodination), a significant degree of cyclization was observed in three cases. In parallel to the conversion of the substrates, the formation of intensely colored by-products was observed. Based on mass spectrometric evidence and upon comparison with known compounds, the by-products were identified as cyanine dyes. Their formation supports the hypothesis that irradiation of dichloromethane solutions of Hünig's base leads to the formation of radicals, which in turn can either initiate a radical reaction or combine with cyanine precursors. It was shown by deuterium-labelling experiments, that one equivalent of dichloromethane is incorporated into the cyanine dyes and that the reductive quenching of radical intermediates is at least partially due to hydrogen abstraction from the solvent. As a consequence, a reductive cyclization of the starting materials is favored in CD Cl solutions as shown for two β-(3-iodopropoxy)-substituted tetronates, which underwent in dichloromethane almost exclusive reduction, but gave predominantly the cyclization products in CD Cl .

Iridium complexes were prepared which are covalently linked via a bipyridine ligand to a chiral octahydro-1H-4,7-methanoisoindol-1-one skeleton. The skeleton allows for two-point hydrogen bonding to prochiral lactams, which can be processed in iridium-catalyzed photochemical reactions. Attempts to use the iridium complexes in reactions, which typically involve photoinduced electron transfer, failed to provide the desired enantioselectivity. If employed as triplet sensitizers the complexes showed an improved performance and moderate enantioselectivities (up to 29% ee) were achieved in a photochemical epoxide rearrangement.

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