Synthesis of Triazatriphenylene Derivative Through Multi-Component Reaction of Aryl-amine, Aldehyde, and Alkyne

Abstract

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.