Catalytic Activation of Skeletal Bonds in Strained Photoproducts

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The activation of skeletal bonds (in particular C-C and C-N) in organic molecules has a high potential for the efficient synthesis of novel molecular frameworks. Due to energetic reasons, such bond activations are, however, difficult to perform. They usually require chelating moieties in combination with reactive (and mostly pricy) transition metal catalysts or strained reactants. The latter substrates can be easily prepared from readily available starting materials by photochemical transformations. The aim of the present project is the search for novel catalytic bond activations of strained photoproducts, their mechanistic investigation as well as the exploration of their applicability for the synthesis of heterocyclic frameworks.The inclusion of heteroatoms (in particular oxygen and nitrogen) will provide additional activation as well as regiocontrol for the bond activations. In addition to classical batch-procedures with pure stable photoproducts, reactions of short-lived intermediates generated in flow photoreactors shall also be investigated. Only few photochemically generated high-energy compounds have been subjected to such bond activations so far and the particularly attractive intermolecular reactions are largely underinvestigated. Nevertheless, the practicability of the general concept could be demonstrated in preliminary investigations and two novel syntheses of imidazoles and pyrroles have already been developed.Ideally, the projected methodology permits the construction of attractive molecular scaffolds by employing UV-light as the sole energy source while avoiding the formation of low-energy co-products (e.g. metal salts, boric acid derivatives) in a sustainable approach.