Search Results (10)

9-Mesitylacridinium salts are widely recognized as efficient organic photoredox catalysts owing to their strong excited-state oxidizing power and stability under visible-light irradiation. In this study, a new mesityl acridinium derivative bearing a di-tert-butylphenyl substituent on the nitrogen atom was synthesized. The introduction of tert-butyl groups on the N-aryl moiety was primarily aimed at improving solubility and chemical stability of the acridinium salt. Starting from a 9(10H)-acridinone precursor, the target compound was obtained in high overall yield through a concise synthetic sequence. The synthesis consists of a copper-catalyzed C–N coupling reaction to install the aryl substituent on the nitrogen atom, followed by a Grignard reaction and subsequent acid treatment to afford the corresponding acridinium salt. All transformations proceeded smoothly, providing efficient access to the desired novel acridinium derivative. This work presents a practical example of the structural modification of mesitylacridinium derivatives directed toward enhanced solubility and stability, and provides a useful synthetic platform for the preparation of structurally diverse acridinium salts. Full article

Triangulene, also known as Clar’s hydrocarbon, has been sought after by chemists for more than 70 years but with limited success. Herein, we report an oxidative dehydrogenation method to synthesize two kinetically blocked [3]triangulene derivatives TRI-1 (reported) and TRI-2 (newly synthesized), in which the three most reactive sites are substituted by bulky mesityl groups and electron-withdrawing 2,4,6-trichlorophenyl groups, and meanwhile, three vertices of triangulene are substituted by tert-butyl groups. Interestingly, the dihydro-triangulene core possesses two isomers well characterized by UV-vis, NMR spectroscopy, and X-ray crystallographic analysis, which is interestingly substituent-dependent. The newly synthesized TRI-2 is isolated in crystalline form, and X-ray crystallographic analysis reveals that the aryl substituents are nearly perpendicular to the triangulene plane and thus cause little perturbation of the electronic properties of the triangulene. Notably, 2,4,6-trichlorophenyl-substituted TRI-2 exhibits enhanced stability compared to the reported mesityl-substituted TRI-1, e.g., TRI-2 is stable for months in a crystalline state under a nitrogen atmosphere, and TRI-2 in a solution state is also more persistent than TRI-1 (half-life for TRI-1 ≈ 18 h vs. TRI-2 ≈ 132 h). This achievement will facilitate the design and synthesis of stable triangulene dimers and oligomers with higher spin multiplicity. Full article

The two naphthol isomers were investigated in different organic solvents by taking cyclic voltammograms, and fouling took place on a platinum electrode surface, except for dimethyl sulfoxide and dimethyl formamide. Studies in allyl alcohol rarely used in electrochemical investigations pointed to the importance of the carbon–carbon double bond as electrode deactivation was remarkably faster compared with its saturated analog solvent. Similarly, the use of the other unsaturated solvent mesityl oxide in the electropolymerization of naphthols resulted in different findings compared with methyl isobutyl ketone. As dimethyl formamide was the best choice concerning the solubility of products, it was successfully tested in electrode renewal after deactivation in an aqueous solution. The increase in dimethyl formamide content led to more and more improved reproducibility of the currents of the outlined aromatic compounds. Naphthol isomers were assessed in the suppression of layer growth originating from the electrooxidation of another monomer phloroglucinol. Its simultaneous electrooxidation with naphthol monomers had a dramatic effect on layer morphology and it was found that instead of a coherent organic layer originating from the homopolymerization of phloroglucinol, the copolymerization with naphthols led to the development of more porous and rougher deposits. The suppressed electropolymerization thus increased sensitivity towards a chosen redox active compound, 4-methoxyphenol. Full article

This study explores the characteristics of electrodeposition of the three hydroxybenzaldehyde isomers and selected hydroxybenzoic acids (4-hydroxybenzoic acid, salicylic acid, 3,5-dihydroxybenzoic acid) from mesityl oxide solvent. Similar to recent advances of this solvent, used by electrochemical studies, the carbon–carbon double bond had significant influence on the formation of polymers from the outlined molecules. In case of most substrates the peak currents increased to a steady-state but electropolymerization of some substrates caused significant deactivation. Scanning electron microscopic and complementary voltammetric studies facilitated that the electrochemically formed polymers are present on the electrode surface in stackings. In viewpoint of analysis of 2-phenylphenol, the modifying deposit formed from 4-hydroxybenzaldehyde was the best with 5 µM detection limit obtained with differential pulse voltammetry. Furthermore, a new procedure was chosen for the involvement of a cavitand derivative into the organic layers with the purpose to improve the layer selectivity (subsequent electrochemical polymerization in an other solution). Further studies showed that in this way the sensitivities of as-modified electrodes were a little worse than without this step, thus indicating that application of this step is disadvantageous. Recovery studies of 2-phenylphenol were carried out on lemon rind without any treatment, and it was compared with the case when the outer yellow layer was removed by rasping. The inner tissues showed very high adsorption affinity towards 2-phenylphenol. Full article

This work deals with the study of the synthesis of new bis-indole analogues with a phenyl linker derived from indole phytoalexins. Synthesis of target bis-indole thiourea linked by a phenyl linker was achieved by the reaction of [1-(tert-butoxycarbonyl)indol-3-yl]methyl isothiocyanate with p-phenylenediamine. By replacing the sulfur of the thiocarbonyl group in bis-indole thiourea with oxygen using mesityl nitrile oxide, a bis-indole homodimer with a urea group was obtained. A cyclization protocol utilizing bis-indole thiourea and methyl bromoacetate was applied to synthesize a bis-indole homodimer with a thiazolidin-4-one moiety. Bis-indole homodimers derived from 1-methoxyspirobrassinol methyl ether were prepared by bromospirocyclization methodology. Among the synthesized analogues, compound 49 was selected for further study. To evaluate the mode of the mechanism of action, we used flow cytometry, Western blot, and spectroscopic analyses. Compound 49 significantly inhibited the proliferation of lung cancer cell line A549 with minimal effects on the non-cancer cells. We also demonstrated that compound 49 induced autophagy through the upregulation of Beclin-1, LC3A/B, Atg7 and AMPK and ULK1. Furthermore, chloroquine (CQ; an autophagy inhibitor) in combination with compound 49 decreased cell proliferation and induced G1 cell cycle arrest and apoptosis. Compound 49 also caused GSH depletion and significantly potentiated the antiproliferative effect of cis-platin. Full article

The electropolymerization of three phenylphenol isomers was studied in methyl isobutyl ketone and mesityl oxide, and the remarkable differences highlighted the importance of the carbon–carbon double bond in mesityl oxide. In the case of each substrate, a brownish deposit formed during the electrooxidation. The obvious difference between the polymers formed from the two solvents was recognized via voltammetric signal enhancement of 4-methoxyphenol and 4-chlorophenol, and it was only observed in the case of mesityl oxide. The experiments highlighted that incorporation of a cavitand with biphenyl groups on the upper rim of the polymers of phenylphenols improved the results to a small extent. The cavitand was, itself, electroactive without any fouling effect. As 2-phenylphenol is by far the cheapest of the three isomers, a cavitand was incorporated into its polymer, which was exploited to solve analytical problems while mesityl oxide was used as solvent. Useful quantifications were achieved in organic solvents; however, it failed under aqueous conditions due to the high hydrophobicity of the deposit. Application of differential pulse voltammetry for 4-methoxyphenol and 4-chlorophenol gave detection limits of 9.28 and 50.8 μM in acetonitrile, respectively. This procedure resulted in the immobilization of cavitand derivatives onto the electrode’s surface, and the layer formed offered selective sensing of phenols by electrochemical methods. Full article

Mesityl oxide is standardly used to produce methyl iso butyl ketone but it can be also used to produce other useful compounds. Three catalysts were used for the reaction of the mesityl oxide reduction. They were NiW, NiMo, and CoMo supported on phonolite modified by HCl (metals/Ph-HCl). The fresh catalysts were characterized by XRD, XRF, BET surface, Hg porosimetry, SEM, H₂-TPR, NH₃-TPD, CO₂-TPD. The materials were directly used, previously reduced in H₂ or sulfided for the mesityl oxide reduction under H₂ atmosphere. The reaction was performed in an autoclave at T = 375 °C, p = 50 bar (H₂), and TOS = 1.5 h. The products were analyzed by GC/MS, GC/FID-TCD, ATR. The main products were methyl isobutyl ketone, 2-methyl pentane, and 2-methyl-2-pentene. Sulfided metal catalysts were the most active in the methyl isobutyl ketone, where the NiWSx/Ph-HCl catalyst showed the highest activity. For the non-previously-activated and hydrogen activated catalysts the most active catalyst was the NiMo/Ph-HCl for the production of methyl isobutyl ketone. The catalyst CoMo/Ph-HCl activated in hydrogen was the most active for the production of 2-methyl pentane compared to the other two hydrogen-activated materials. Full article

A series of free base meso-tetraarylporphyrins functionalized with substituents containing one, two, and four cyclooctatetraene (COT) moieties have been obtained and characterized by spectral and photophysical studies. Three COT-free porphyrins served as reference compounds. COT is a triplet quencher, well-known to enhance the photostability of several, but not all, fluorophores. In the case of porphyrins, substitution with COT improves photostability in zinc derivatives, but for free bases, the effect is the opposite. We show that placing the COT moiety further from the free base porphyrin core enhances the photostability when the COT group lies in the direct vicinity of the macrocycle. The quantum yields of photobleaching inversely correlate with porphyrin oxidation potentials. An improvement in photostability in both COT-containing and COT-free porphyrins can be achieved by screening the porphyrin core from oxygen by switching from tolyl to mesityl substituents. This leads to a decrease in the photobleaching quantum yield, even though triplet lifetimes are longer. The results confirm the involvement of oxygen in the photodegradation of porphyrins. Full article

An aroma-based method for distinguishing different grades of Nongxiang Tieguanyin was explored by taking special grade (K110) and 1–4 grades (K101, K102, K103, and K104) of this tea as samples. Tea samples were analyzed by gas chromatography–mass spectrometry (GC-MS) combined with chemometrics. Results showed differences in the types and relative contents of aroma components among different grades of Nongxiang Tieguanyin tea. In the principal component analysis (PCA) scoring plot, except for K102 and K103, tea samples of different grades were distributed in different regions. Components satisfying variable important for the projection (VIP) > 1 and peak areas with significant differences (p < 0.05) among different tea grades were screened. Finally, 18 differential variables were screened out from 143 volatiles. The clustering results of these variables were consistent with those of PCA. K102 and K103 were initially clustered into one group and then clustered with K101, K110, and K104 in turn. The clear PCA separation of these samples and uniform hierarchical cluster analysis (HCA) clustering results suggests that GC-MS coupled with chemometrics analysis is a valid and accurate approach for discriminating different grades of Nongxiang Tieguanyin. The screened differential variables could represent a difference in aroma quality among five grades of Nongxiang Tieguanyin tea. Clear rules between peak area and the grade were also observed in some differential variables. 1-Ethylpyrrole and unknown-32 were positively correlated with grade. 2-Methylfuran, 2-ethylfuran, 2-methylidenecyclopentan-1-ol, mesityl oxide, 2-amylfuran, and D-limonene were negatively correlated with grade. The peak areas of methyl acetate, dimethyl sulfide, 6-methylhept-5-en-2-one, and (Z)-β-ocimene initially decreased but then increased with declining grade. The toluene content was especially high in K104 but only a negligible difference was observed among other grades. This study provides a potential method for differentiating Nongxiang Tieguanyin teas of different grades based on aroma. Unknown samples could be classified by comparison of their spatial distribution with those of known standard samples in PCA or HCA, as well as the peak area differences of differential variables between unknown samples and known standard samples. Full article

A capillary gas chromatography method with a short run time, using a flame ionization detector, has been developed for the quantitative determination of trace level analysis of mesityl oxide and diacetone alcohol in the atazanavir sulfate drug substance. The chromatographic method was achieved on a fused silica capillary column coated with 5% diphenyl and 95% dimethyl polysiloxane stationary phase (Rtx-5, 30 m x 0.53 mm x 5.0 µm). The run time was 20 min employing programmed temperature with a split mode (1:5) and was validated for specificity, sensitivity, precision, linearity, and accuracy. The detection and quantitation limits obtained for mesityl oxide and diacetone alcohol were 5 µg/g and 10 µg/g, respectively, for both of the analytes. The method was found to be linear in the range between 10 µg/g and 150 µg/g with a correlation coefficient greater than 0.999, and the average recoveries obtained in atazanavir sulfate were between 102.0% and 103.7%, respectively, for mesityl oxide and diacetone alcohol. The developed method was found to be robust and rugged. The detailed experimental results are discussed in this research paper. Full article