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Fernandez, Sarah; Ganiek, Maximilian A.; Karpacheva, Mariia; Hanusch, Fabian C.; Reuter, Stephan; Bein, Thomas; Auras, Florian; Knochel, Paul (2016): Synthesis and Reactivity of Triazaphenanthrenes. In: Organic Letters, Vol. 18, No. 13: pp. 3158-3161
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Pyridonaphthyridines (triazaphenanthrenes) were prepared in 4 steps and in 13-52% overall yield using Negishi cross-couplings between iodopicolines and 2-chloropyridylzinc derivatives. After chlorination, Gabriel amination and spontaneous ring-closure, the final aromatization leading to the triazaphenanthrenes was achieved with chloranil. This heterocyclic scaffold underwent a nucleophilic addition at position 6 leading to further functionalized pyridonaphthyridines. The influence of these chemical modifications on the optical properties was studied by steady-state and time-resolved optical spectroscopy. While the thiophene-substituted heterocycles exhibited the most extended absorption, the phenyl- and furan-substituted" compounds showed a stronger photoluminescence, reaching above 20% quantum yield and lifetimes of several nanoseconds.