Search

Thermal, structural, and photophysical properties of five pyrazolo[1,5‐a]pyrimidine‐triphenylamine hybrid systems substituted at position 3 of the fused ring were studied (probe/R: D1/H, D2/I, D3/CCSiMe3, D4/CHO, D5/CN). The solvatofluorochromism of D4 and D5 showed that the solvent dipolarity (SdP) is mainly responsible for their spectral changes, which arose from an internal charge transfer (ICT) from the triphenylamine (TPA) group to the acceptor substituent at position 3. As a result, D5 was applied for the detection of water in organic solvents (i. e., AcOEt and THF); this probe also exhibited an intense light emission in the solid‐state at 530 nm (ϕ=0.60). The five compound structures were solved and analyzed by X‐ray crystallography (XRC), with a link found between their structural characteristics and their physicochemical properties. For example, although all the probes exhibited good thermostabilities, this property decreased in D3 and was explained by frontier molecular orbital calculations based on the XRC results. Crystallographic studies were also used to interpret the differences in solid‐phase emission intensities in D1–D4 versus D5. [ABSTRACT FROM AUTHOR]

This work describes the synthesis and antifungal evaluation of 5-arylidene-( Z)-2-(1,1-dicyanomethylene)-1,3-thiazol-4-ones obtained from the reaction of 2-(1,1-dicyanomethylene)-1,3-thiazol-4-one and benzaldehydes . The starting material was synthesized by a condensation reaction of rhodanine and malononitrile . The structures of the obtained products were established by IR, NMR, mass spectrometry, and elemental analysis. J. Heterocyclic Chem., (2011). [ABSTRACT FROM AUTHOR]

An operably simple microwave-assisted BF 3 -mediated acetylation reaction of pyrazolo[1,5- a ]pyrimidines and a plausible mechanism based on density functional theory (DFT) theoretical calculations for this transformation are reported. Remarkably, and to the best of our knowledge, this is the first example of the direct acetylation for the functional pyrazolo[1,5- a ]pyrimidine (PP) core. The synthesis of this essential building block is reported in high yields using mild reaction conditions, inexpensive reagents, and even substrates with electron-deficient or highly hindered groups. In addition, one of the new methyl ketones was successfully used as a substrate for producing novel and valuable bis-electrophilic compounds with yields of up to 90%. Notably, the discovered acetylation method was successfully applied in other π-excedent ( N -hetero)aromatic substrates.

Fluorescent molecules are crucial tools for studying the dynamics of intracellular processes, chemosensors, and the progress of organic materials. In this study, a family of pyrazolo[1,5- a ]pyrimidines (PPs) 4a-g has been identified as strategic compounds for optical applications due to several key characteristics such as their simpler and greener synthetic methodology (RME: 40-53%) as compared to those of BODIPYS (RME: 1.31-17.9%), and their tunable photophysical properties (going from ε = 3320 M -1 cm -1 and ϕ F = 0.01 to ε = 20 593 M -1 cm -1 and ϕ F = 0.97), in which electron-donating groups (EDGs) at position 7 on the fused ring improve both the absorption and emission behaviors. The PPs bearing simple aryl groups such as 4a (4-Py), 4b (2,4-Cl 2 Ph), 4d (Ph) and 4e (4-MeOPh), allow good solid-state emission intensities (QY SS = 0.18 to 0.63) in these compounds and thus, solid-state emitters can be designed by proper structural selection. The properties and stability found in 4a-g are comparable to commercial probes such as coumarin-153, prodan and rhodamine 6G. Ultimately, the electronic structure analysis based on DFT and TD-DFT calculations revealed that EDGs at position 7 on the fused ring favor large absorption/emission intensities as a result of the ICT to/from this ring; however, these intensities remain low with electron-withdrawing groups (EWGs), which is in line with the experimental data and allows us to understand the optical properties of this fluorophore family., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)

An efficient and quick access toward a series of ( E )-2-arylideneaminopyrroles 6 and to their benzyne-promoted aza-Diels-Alder cycloaddition products is provided. These products are three pyrrolo[2,3- c ]isoquinolines 8a-c substituted in position 5 with different electron-acceptor (A) or electron-donor (D) aryl groups. Intermediates and products were obtained in good yields (up to 78 and 84%, respectively), and their structures were determined on the basis of NMR measurements and HRMS analysis. Photophysical properties of 8a-c were investigated, finding good Stokes shift in different solvents, but only the product 8c showed appreciable fluorescence intensity since its 5-aryl group (2,4-Cl 2 Ph) could favor the twisted intramolecular charge transfer effect. In addition, a riveting relationship between solvent viscosity and fluorescence intensity was found. Structures of 6 and 8 were studied and confirmed by single-crystal X-ray diffraction, observing that their electronic distributions effect the supramolecular assembly but with only long-distance hydrophobic interactions. A CE-B3LYP model was used to study the energetic topology and understand the crystal architecture of compounds as well as find a connection with both the synthetic and photophysical results., Competing Interests: The authors declare no competing financial interest., (Copyright © 2019 American Chemical Society.)