2-(2’-Hydroxyphenyl)benzazole dyes are particularly interesting molecules that exhibit excited-state intramolecular proton transfer (ESIPT) following photoexcitation. In 1957, Hein employed polyphosphoric acid as both a solvent and dehydrating agent to synthesize a series of 2‑aryl-substituted benzimidazoles, benzoxazoles, and benzothiazoles, which had previously been inaccessible. However, the harsh reaction conditions for an extended period produce side reactions, and even carbonization inevitably can occur. Since this method continues to be used widely, in our work we have done time-dependent experiments to verify whether it would be possible to shorten reaction time. For this, the synthesis of a series of 2‑(2’-hydroxyphenyl)benzazole dyes from anilines ortho-substituted with aromatic carboxylic acids in polyphosphoric acid was monitored over time through 1H, 13C NMR, UV-vis, and fluorescence spectroscopies. Our results showed that all reagents were consumed, and the expected dyes were formed within an hour of reaction with yields ranging from 30 to 96
Photophysical, solvatochromic, and electronic properties of the azo dye (E)-1-[(3-hydroxy-2-oxo‑2H-chromen-4-yl)diazenyl]anthracene‑9,10-dione were investigated by experimental and theoretical methods. UV-visible absorption and fluorescence emission spectra recorded in solvents of varying polarity revealed pronounced positive solvatochromism, accompanied by large Stokes shifts that increase in polar and hydrogen-bonding media. Solute-solvent interactions were quantitatively analyzed using the Catalán multiparameter model, demonstrating that polarizability, dipolarity, and both acidic and basic hydrogen-bonding interactions significantly stabilize the excited state. Density functional theory calculations revealed a nearly planar structure with strong π‑conjugation across the azo bridge. Frontier molecular orbital analysis showed that the HOMO is primarily localized on the anthraquinone moiety, while the LUMO is distributed over the azocoumarin fragment, confirming intramolecular charge transfer with a calculated energy gap of 3.121 eV. Natural transition orbital (NTO) analysis provided a clear visualization of the excitation process, revealing hole localization on the anthraquinone unit and electron density on the azocoumarin segment, thereby confirming directional charge transfer in the excited state. This is further supported by quantitative hole-electron analysis, indicating significant charge separation. Global chemical reactivity descriptors suggest that this dye is a soft electrophilic system with high electron affinity (2.858 eV) and electrophilicity index (6.372 eV). When implemented in a TiO2-based dye-sensitized solar cell under AM 1.5G illumination, E‑AN exhibited a short-circuit current density of 19.3 mA·cm−2, an open-circuit voltage of 0.257 V, a fill factor of 39.5
This microreview summarizes mainly the literature from the last seven years on the application of oxime esters in the synthesis of 1,3-thiazoles and related structures. The material is systematized in accordance with the structure of the obtained compounds.
Frizzled receptors, central to Wnt/β-catenin signaling, are promising targets for enhancing wound healing. This exploratory study evaluates the wound healing potential of 2‑(4-isopropylphenyl)-5-nitrobenzoxazole, a benzoxazole derivative, through a combined in vitro scratch assay and molecular docking analysis. Normal human dermal fibroblasts were treated with 2‑(4-isopropylphenyl)-5-nitrobenzoxazole at 10, 1, and 0.1 µM, and wound closure was assessed at 0, 16, 24, and 40 h. Although no statistically significant differences in migration were observed, time-dependent increases in the motility index were consistent across all groups. Molecular docking against Frizzled (PDB ID: 6TFB) demonstrated stable binding of 2‑(4-isopropylphenyl)-5-nitrobenzoxazole, supported by a favorable docking score (−5.746) and key interactions with Gln56, Phe57, and Pro103. These findings suggest that IPNB may interact with the Frizzled receptor without impairing fibroblast migration, warranting further mechanistic studies. This represents the first report of a benzoxazole derivative evaluated for Frizzled modulation in a wound healing context.
