The Povarov reaction combines aromatic amines, aldehydes, and alkynes in a single step and is regarded as an annulative π-extension reaction of aromatic amines. In this study, the Povarov reaction was investigated as an efficient tool for the synthesis of aza-polycyclic aromatic hydrocarbons via multiple π-extensions. The double Povarov reaction of 1,4-diaminobenzene yielded the 4,7phenanthroline derivative as the major product, regardless of the steric repulsion in the product. The site selectivity mainly depended on the HOMO distribution of the intermediate rather than the steric factor. Based on these insights, a 1,5,9-triazatriphenylene derivative was synthesized via a triple Povarov reaction. The structures of the synthesized compounds were unambiguously determined by single-crystal X-ray diffraction analysis. The triazatriphenylene derivative formed a smooth and stable thin film upon vacuum vapor deposition and served as a hole-blocking material in organic light-emitting diodes.

Phenanthroline derivatives are typical simple aza-polycyclic aromatic hydrocarbons that have been used as hole-blocking and electron-transporting materials in organic light-emitting diodes (OLEDs). In contrast to the widely used 1,10-phenanthroline derivatives, other isomers, including 1,7-phenanthrolines, have been explored less, partly due to the lack of effective and selective synthesis methods. This study demonstrates the facile synthesis of 1,7-phenanthroline derivatives bearing various substituents via a multicomponent reaction based on the aza-Diels-Alder reaction. By investigating the correlation between the substituents and their performance as hole-blocking materials in OLEDs, we gained insight into the molecular design of 1,7-phenanthroline derivatives for material applications.

The Povarov reaction is a representative multicomponent reaction used for synthesizing nitrogen‐containing aromatic compounds from aromatic amines, aldehydes, and dienophiles, such as electron‐rich alkenes and alkynes. In this study, we investigated a triple Povarov reaction of 1,3,5‐triaminobenzne with aromatic aldehydes and phenylacetylene to obtain triazatriphenylene derivatives. Reactions with arylaldehydes containing electron‐donating groups proceeded smoothly to provide triazatriphenylene derivatives. In contrast, reactions with arylaldehydes containing electron‐withdrawing groups resulted in low yields. Reactions with electron‐rich arylaldehydes are probably more favorable in terms of high stability of imine intermediates and smooth electrophilic cyclization. Single‐crystal X‐ray structure analysis revealed that the aryl groups derived from the aldehydes had small dihedral angles between with the triazatriphenylene core. The derivative with tertiary butyl groups (tBu‐TaT) had a high glass transition temperature, while that without tertiary butyl groups (H‐TaT) had a lower highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) level and served as an efficient hole‐blocking material with better electron transport properties than those of tBu‐TaT. This study provides insights into the scope and limitations of the multicomponent reactions based on the Povarov reaction, substituent dependence on the crystal structures, and physical properties of π‐extended nitrogen‐containing aromatic compounds.