Synthesis and Properties of 5-Azaullazines

Divergent Synthesis of 5,7-Diazaullazines Derivatives through a Combination of Cycloisomerization with Povarov or Alkyne-Carbonyl Metathesis

Ullazines and their π-expanded derivatives have gained much attention as active components in various applications, such as in organic photovoltaic cells or as photosensitizers for CO2 photoreduction. Here, we report the divergent synthesis of functionalized diazaullazines by means of two different domino-reactions consisting of either a Povarov/cycloisomerization or alkyne-carbonyl metathesis/cycloisomerization protocol. The corresponding quinolino-diazaullazine and benzoyl-diazaullazine derivatives were obtained in moderate to good yields. Their optical and electronic properties were studied and compared to related, literature-known compounds to obtain insights into the impact of nitrogen doping and π-expansion.

π-Expanded azaullazines: synthesis of quinolino-azaullazines by Povarov reaction and cycloisomerisation

Doping and extension of polycyclic aromatic hydrocarbons (PAHs) by simple and efficient synthetic methods is of increased demand for the development of novel and improved organic electronics. Diarylindolizino[6,5,4,3-ija]quinolino[2,3-c][1,6]naphthyridines (quinolino-azaullazines) were prepared by combination of Pd catalyzed cross-coupling with Povarov and cycloisomerisation reactions. The products contain an electron-rich ullazine and an electron-poor quinoline moiety and show intramolecular charge transfer properties that can be tuned by the substitution pattern. The optical properties were studied experimentally and further elaborated by (TD)DFT calculations.

Synthesis and Properties of 5,7-Diazaullazines

Hitherto unknown 5,8-substituted-pyrimido[4,5,6-ij]pyrrolo[2,1,5-de]quinolizines (5,7-diazaullazines) were prepared by a three-step synthesis via Clauson-Kaas, Sonogashira, and cycloisomerization reactions with diverse functionalization. The properties, including cyclovoltammetry and UV-vis and fluorescence spectroscopy, as well as solvatochromism, were studied for selected derivatives and supported by density functional theory calculations. Results were compared in detail with previously reported 5- and 6-azaullazines, and the impact of introduced nitrogen atoms was analyzed.