Thiophene ring-fragmentation reactions: Principles and scale-up towards NLO materials

Anticancer potential of new 3-nitroaryl-6-(N-methyl)piperazin-1,2,4-triazolo[3,4-a]phthalazines targeting voltage-gated K+ channel: Copper-catalyzed one-pot synthesis from 4-chloro-1-phthalazinyl-arylhydrazones

A series of six 3-aryl-6-(N-methylpiperazin)-1,2,4-triazolo[3,4-a]phthalazines were prepared through a facile and efficient one-pot copper-catalyzed procedure from 4-chloro-1-phthalazinyl-arylhydrazones with relatively good yields (62-83%). The one-pot copper-catalytic procedure consists of two simultaneous reactions: (i) a direct intramolecular dehydrogentaive cyclization between ylidenic carbon and adjacent pyrazine nitrogen to form 1,2,4-triazolo ring and, (ii) a direct N-amination on carbon-chlorine bond. Then, an in vitro anticancer evaluation was performed for the synthesized compounds against five selected human cancer cells (A549, MCF-7, SKBr3, PC-3 and HeLa). The nitro-derivatives were significantly more active against cancer strains than against the rest of tested compounds. Specifically, compound 8d was identified as the most promising anticancer agent with significant biological responses and low relative toxicities on human dermis fibroblast. The cytotoxic effect of compound 8d was more significant on PC3, MCF-7 and SKBr3 cancer cells with low-micromolar IC₅₀ value ranging from 0.11 to 0.59 μM, superior to Adriamycin drug. Mechanistic experimental and theoretical studies demonstrated that compounds 8d act as a K⁺ channel inhibitor in cancer models. Further molecular docking studies suggest that the EGFR Tyrosine Kinase enzyme may be a potential target for the most active 3-aryl-6-(N-methylpiperazin)-1,2,4-triazolo[3,4-a]phthalazines.

Recent advances in organic dyes and fluorophores comprising a 1,2,3-triazole moiety

Since the discovery of the copper catalyzed azide alkyne cycloaddition in the early 2000s, tremendous efforts have been devoted to enlarging the scope of applications of this relatively simple to handle reaction.

Optimization of phthalazin-based aryl/heteroarylhydrazones to design new promising antileishmanicidal agents: synthesis and biological evaluation of 3-aryl-6-piperazin-1,2,4-triazolo[3,4-a]phthalazines

1-Monosubstituted and 1,4-substituted phthalazins based on aryl/heteroarylhydrazinyl have demonstrated attractive antileishmanial profiles against amastigote forms of the Leishmania braziliensis parasite.

Regiocontrolled Halogen Dance of Bromothiophenes and Bromofurans

The LDA (lithium diisopropylamide)-promoted regiocontrolled halogen dance of α-bromothiophenes and α-bromofurans is described. Bromothiophenes bearing a diethyl acetal moiety undergo selective deprotonation at the β-position adjacent to the bromo group. In contrast, oxazoline, ester, and amide groups act as directing groups in the initial lithiation step to generate a carbanion at the β-position neighboring the directing group to exclusively give the other regioisomer. These results can be applied to the regiocontrolled halogen dance of bromofuran derivatives.

A novel selenoalkenyl-isoxazole based donor-acceptor nonlinear optical material

The structure property relationships of untwinned enantiomorphic Z-(methylseleno)alkenyl-substituted phenyl-isoxazole and its isostructural triazole congener both crystallizing in the P2₁2₁2₁ space group were investigated with respect to UV/vis absorption, thermal behaviour, and second harmonic generation ability. Differential scanning calorimetry revealed a significantly higher melting point of the novel isoxazole compound compared to the triazole derivative and therefore a broader thermal application window. The SHG efficiency of the isoxazole derivative is approximately two thirds the value of the triazole compound and approximately 27 times higher than potassium dihydrogen phosphate. Thus, the developed molecular scaffold represents an interesting novel type of nonlinear optical (NLO) chromophore.

Charge-transfer states in triazole linked donor-acceptor materials: strong effects of chemical modification and solvation

A series of 1,2,3-triazole linked donor-acceptor chromophores are prepared by Click Chemistry from ene-yne starting materials. The effects of three distinct chemical variations are investigated: enhancing the acceptor strength through oxidation of the sulphur atom, alteration of the double bond configuration, and variation of the triazole substitution pattern. A detailed photophysical characterization shows that these alterations have a negligible effect on the absorption while dramatically altering the emission wavelengths. In addition, strong solvatochromism is found leading to significant red shifts in the case of polar solvents. The experimental findings are rationalized and related to the electronic structure properties of the chromophores by time-dependent density functional theory as well as the ab initio algebraic diagrammatic construction method for the polarization propagator in connection with a new formalism allowing to model the influence of solvation onto long-lived excited states and their emission energies. These calculations highlight the varying degree of intramolecular charge transfer character present for the different molecules and show that the amount of charge transfer is strongly modulated by the conducted chemical modifications, by the solvation of the chromophores, and by the structural relaxation in the excited state. It is, furthermore, shown that enhanced charge separation, as induced by chemical modification or solvation, reduces the singlet-triplet gaps and that two of the investigated molecules possess sufficiently low gaps to be considered as candidates for thermally activated delayed fluorescence.