Position Of Benzene Ring Research Articles

Structure, Thermal Properties and Proton Conductivity of the Sulfonated Polyphenylquinoxalines

This paper briefly reviews the results of scientific research on the proton conductivity of sulfonated polyphenylquinoxalines. Synthesis, structure (IR spectroscopy, SEM, quantum-chemical modeling, molecular weight distribution), moisture capacity, thermal properties, and proton conductivity of sulfonated polyphenylquinoxalines (sulfur content 2.6, 4.2, 5.5, and 7%) were studied. The relative stable configurations of sulfonated polyphenylquinoxalines with different positions of benzene rings and sulfogroups with the help of quantum chemical modeling were modeled. Sulfonation of the starting polyphenylquinoxalines was confirmed by IR spectroscopy and elemental analysis. The SEM method was used to study the surface of sulfonated polyphenylquinoxalines, and sulfonation regions were found. It was shown that sulfonated polyphenylquinoxalines contain water and are stable up to 250 °C; on further heating, the decomposition of the sulfogroups occurs. The conductivity of the obtained polymer electrolytes was studied by impedance spectroscopy, and long-term tests were carried out. It is shown that the proton conductivity at an ambient humidity of 98 rel. % reaches values 10-6-10-3 S/cm depending on the degree of sulfonation. It was shown that even after long-term storage in air (7 years), samples of sulfonated polyphenylquinoxalines with a high sulfur content of 7% at 98% air humidity have a conductivity of 8 × 10-4 S/cm.

The upcycling of polyethylene terephthalate using protic ionic liquids as catalyst

The recycling of waste PET is of great significance to alleviate environmental pollution and resource depletion. Ionic liquid, as environmentally friendly “green” solvent, has been applied in PET glycolysis. However, most of ionic liquids have some defects such as the cost and relatively complex preparation process, which is not conducive to its practical application. Herein, a series of protic ionic liquids were synthesized by simply mixing Bronsted acid and Bronsted base to catalyze PET glycolysis. The influence of different anion on PET glycolysis was investigated and results suggested that anion containing electron donating group (CH3-) has ideal activity and the electron donating group at different position of benzene ring also affects catalytic performance of protic ionic liquids. 1H NMR spectrum of PIL-EG system and DFT calculation showed that there is interaction between ethylene glycol and protic ionic liquid and presence of hydrogen transfer process in PET glycolysis catalyzed by protic ionic liquid. Possible reaction pathway was proposed. At optimal reaction condition, PET conversion is 100% and BHET yield reached 87.3% using PIL3 as catalyst. Moreover, protic ionic liquid still has excellent catalytic performance after being reused for eight times. The kinetic of PET glycolysis catalyzed by PIL3 was explored and apparent activation energy is 162.82 kJ/mol.

Synthesis, antimicrobial activity and 3D-QSAR study of novel 5-substituted-1,3,4-thiadiazole Schiff base derivatives

In this study, 21 new thiadiazole Schiff base derivatives were synthesized based on the reactive group splicing principle, and the structures of the target compounds were confirmed and characterized by 1H NMR, FT-IR and HRMS. The inhibition activity of the compounds was tested in vitro against Escherichia coli, Staphylococcus aureus, Aspergillus niger, Rhizopus, Penicillium, Botrytis cinerea and Alternaria using mycelial growth rate method. The results showed that most of the compounds exhibited good biological activity at a dose of 50 µg/mL. Among them, compounds 2b, 2r, and 2a exhibited inhibition rates against the tested microbe comparable to that of the control drug Chlorothalonil. A preliminary three-dimensional quantitative conformational relationship (3D-QSAR) study of the inhibitory activity of the target compounds against Aspergillus niger was carried out using CoMFA and CoMSIA, and the model results showed that increasing the volume of the 2- and 6-positions of benzene ring A and the 3-position substituent of benzene ring B, decreasing the volume of the 5-position substituent benzene ring A; increasing hydrophobic groups at the 6-position of benzene ring A and the 2′-position of benzene ring B; increasing the 3′-position hydrogen bond donor group and decreasing the 3′-position hydrogen bond acceptor group of benzene ring B can improve the biological activity of the compounds. The inhibitory activity of the compounds can be improved.

In silico, synthesis and anticancer evaluation of benzamide tryptamine derivatives as novel eEF2K inhibitors

Eukaryotic elongation factor 2 kinase (eEF2K), a member of the atypical α-kinase family, is highly expressed in a variety of tumor tissues. Inhibition of eEF2K function can effectively kill cancer cells without affecting the function of normal cells. Therefore, eEF2K is a promising new target for cancer therapy. In this study, a series of benzamide tryptamine derivatives were designed and synthesized as novel eEF2K inhibitors. The druggability properties of the synthesized compounds were predicted in silico and performed well. The MTT assay indicated that most of these compounds displayed good antiproliferative activity against human leukemia CCRF-CEM and K562 cell lines. The structure–activity relationship (SAR) revealed that substituents with different electronic effects on the C5 position of indole ring or C2′, C4′ positions of benzene ring have a great influence on the anti-proliferative activity. Among them, 5j demonstrated the highest anti-proliferative activity with IC50 value of 1.63–3.54 μM. this compound displayed an effective eEF2K inhibition by down-regulated the level of phosphorylated eEF2 in CCRF-CEM cells. Additionally, the western blot analysis further revealed that 5j also significantly affected eEF2K-related signaling pathways. Anticancer mechanism studies have shown that 5j arrested the cell cycle in G0/G1 and induced CCRF-CEM cells apoptosis. Furthermore, 5j activated cleaved caspase-9, 8, 3 and cleaved PARP in a time-dependent manner, which suggesting that 5j induced cancer cells apoptosis through both intrinsic and extrinsic pathways. In summary, benzamide tryptamine derivative 5j represents a novel and promising lead structure for the development of eEF2K inhibitors in cancer therapy.

Актуальність проблеми визначення діоксинів і поліхлорованих біфенілів (ПХБ) у продуктах для дитячого харчування

The Aim of the Article. Analysis of the current state of the problem of the dioxins and polychlorinated biphenyls (PCBs) determination in baby food products and the development of sample preparation methods for determining these xenobiotics in food products for infants and young children. Dioxins form a group of structurally and chemically related chlorinated tricyclic oxygen-containing aromatic compounds (congeners), which includes 75 polychlorinated dibenzo-para-dioxins (PCDDs) and 135 polychlorinated dibenzofurans (PCDFs). The most toxic congeners of dioxins, in which chlorine atoms along with other positions are necessarily in 2,3,7,8 positions of benzene rings. Their total number is 17:7 PCDD congeners and 10 PCDF congeners. A group of polychlorinated biphenyls (PCBs) – chlorinated bicyclic aromatic compounds, which consists of 209 different congeners, 12 of which have a spatial and electronic structure and exhibit toxicological properties similar to dioxins, therefore, they are called dioxin-like PCBs (DL-PCBs). In addition, when monitoring food products as a marker, a group of 6 PCBs was selected that did not exhibit dioxin-like toxicity and therefore did not belong to dioxin-like PCBs (NDL-PCBs). Thus, of the total number of 419 PCDDs, PCDFs and PCBs, only 35 are toxicologically significant, therefore, these compounds are subject to control in baby food products. To control the content of the amount of dioxins, the amount of dioxins and DL-PCBs and the amount of NDL-PCBs in foods for infants and children from one to three years in Ukraine, the maximum levels of these compounds on the basis of the order of the Ministry of Health of Ukraine No. 368 of 05/13/2013 were harmonized with the maximum allowable levels in foods for infants and young children in accordance with Commission Regulation (EU) No. 1259/2011. Methods for the analysis of dioxins and PCBs. Two instrumental analysis methods are used to determine dioxins and dioxin-like PCBs in foods for baby food: 1) a combination of high-resolution (capillary) gas chromatography with high-resolution mass spectrometry (GC/MS); 2) a combination of GCHR with tandem mass spectroscopy (GC/MS/MS). High-resolution (capillary) gas chromatography is used to determine non-dioxin-like (marker) PCBs. The stage of sample preparation, including the stages of extraction and purification, is key in determining dioxins and PCBs. Conclusions. The stage of sample preparation using automatic devices (liquid extraction under pressure, an automated extract purification system) and chromatographic columns was developed to further determine the mass concentration of dioxins and PCBs in baby food products. The developed procedures using devices for the automatic extraction and purification of the obtained extracts from baby food samples will make it possible in the future to determine PCDDs/PCDFs, ortho-unsubstituted, mono-ortho-substituted and marker PCBs in one sample. Key Words: dioxins, polychlorinated biphenyls, baby food.

INTERACTION OF 2,4- AND 3,4-BIS(TRIFLUOROACETOXY)BENZOATES WITH SULFUR TETRAFLUORIDE IN ANHYDROUS HYDROGEN FLUORIDE SOLUTION

Interaction of methyl 3,4-bis(trifluoroacetoxy)benzoate, methyl and ethyl 2,4-bis( trifluoroacetoxy)benzoates with sulfur tetrafluoride in anhydrous hydrogen fluoride solution has been investigated. On the first stage methyl 3,4-dihydroxybenzoate, methyl 2,4-dihydroxybenzoate and ethyl 2,4-dihydroxybenzoate were obtained by esterification of appropriate acids with respective alcohols using concentrated sulfuric acid as a catalyst. On the second stage obtained dihydroxybenzoates were treated with excess of trifluoroacetic anhydride in autoclave at 150 °C for 5 hours. Then, obtained 2,4- and 3,4-bis(trifluoroacetoxy)benzoates were treated with sulfur tetrafluoride in anhydrous hydrogen fluoride solution at 35 °C for 7 hours under continuous stirring. In such conditions methyl 3,4-bis(trifluoroacetoxy)benzoate transforms into methyl 3,4-bis(pentafluoroethoxy)benzoate with high yield. Unexpectedly, methyl and ethyl 2,4-bis(trifluoroacetoxy)benzoate didn’t undergo similar transformations when treated the same way. Instead of respective bis(pentafluoroethoxy)benzoates, methyl and ethyl 2-hydroxy-4-pentafluoroethoxybenzoates were isolated from the reaction mixture. Obviously, fluorination of trifluoroacetoxy group in the 2 position of benzene ring didn’t take place because of the steric hindrance made by ester group, so 4-pentafluoroethoxy-2- trifluoroacetoxy benzoates were formed. The last compounds were turned to 2-hydroxy-4- pentafluoroethoxybenzoates after quenching the reaction mixture with water. Hydrolysis of obtained methyl 3,4-bis(pentafluoroethoxy)benzoate and methyl and ethyl 2-hydroxy-4-pentafluoroethoxybenzoates with water-alcohol alkaline solution and further acidification of reaction mixture with concentrated hydrochloric acid led to the formation of firstly prepared 3,4-bis(pentafluoroethoxy)benzoic and 2-hydroxy-4-pentafluoroethoxybenzoic acids, respectively. The last one is new fluorine-containing analogue of salicylic acid. The molecular mass of the compounds subject to this study was confirmed by EI-MS and GC/ MS analysis.

Benzoylthioureas: Design, Synthesis and Antimycobacterial Evaluation.

New drugs and strategies to treat tuberculosis (TB) are urgently needed. In this context, thiourea derivatives have a wide range of biological activities, including anti-TB. This fact can be illustrated with the structure of isoxyl, an old anti-TB drug, which has a thiourea as a pharmacophore group. The aim of this study is to describe the synthesis and the antimycobacterial activity of fifty-nine benzoylthioureas derivatives. Benzoylthiourea derivatives have been synthesized and evaluated for their activity against Mycobacterium tuberculosis using the MABA assay. After that, a structure-activity relationship study of this series of compounds has been performed. Nineteen compounds exhibited antimycobacterial activity between 423.1 and 9.6 μM. In general, we observed that the presence of bromine, chlorine and t-Bu group at the para-position in benzene ring plays an important role in the antitubercular activity of Series A. These substituents were fixed at this position in benzene ring and other groups such as Cl, Br, NO2 and OMe were introduced in the benzoyl ring, leading to the derivatives of Series B. In general, Series B was less cytotoxic than Series A, which indicates that the presence of a substituent at benzoyl ring contributes to an improvement in both antimycobacterial activity and toxicity profiles. Compound 4c could be considered a good prototype to be submitted to further structural modifications in the search for new anti-TB drugs, since it is 1.8 times more active than the first line anti-TB drug ethambutol and 0.65 times less active than isoxyl.

Reductive bromination of N, N-bis(4-tert-butylphenyl)hydroxylamine

Unlike most arenes, N, N-bis(4-tert-butylphenyl)hydroxylamine reacts with Br2via the reductive bromination mechanism. Here, two hydrogens in ortho positions of benzene rings are substituted by Br2 and provide two-electron reduction of hydroxylamine to amine.

Structure effect of carbazole-oxadiazole based organic small molecule hosts on the solution-processed phosphorescent OLEDs performance

A group of solution-processed bipolar small molecular host materials, namely 1,4-bis(5-(9-(2-ethylhexyl)-9H-carbazol-3-yl)-1,3,4-oxadiazol-2-yl)benzene (p-BCOB), 1,3-bis(5-(9-(2-ethylhexyl)-9H-carbazol-3-yl)-1,3,4-oxadiazol-2-yl)benzene (m-BCOB) and 1,3,5-tris(5-(9-(2-ethylhexyl)-9H-carbazol-3-yl)-1,3,4-oxadiazol-2-yl)benzene (TCOB) were synthesized by means of connecting carbazole-oxadiazole substituents on the para-, meta- and 1,3,5-meta- positions of benzene ring respectively. The influence of different linking positions of carbazole-oxadiazole substituents on the thermal, photophysical, electrochemical and charge transport properties of the compounds is comprehensively studied. For verifying the host configuration effect on the performance of phosphorescent organic light-emitting diodes (PHOLEDs), solution-processed green and red PHOLEDs with fac-tris(2-phenylpyridine)iridium (Ir(ppy)3) and bis(1-phenylisoquinolinato)(acetylacetonate) iridium (Ir(piq)2acac) as phosphorescent dopants were fabricated. The m-BCOB:Ir(ppy)3 and TOCB:Ir(ppy)3 PHOLEDs show excellent device performance with the maximum luminance efficiencies of 15.0cdA−1 and 13.7cdA−1, respectively, which are increased by 9.8 and 9.0 times compared with the p-BCOB:Ir(ppy)3 PHOLED because of effective Förster and Dexter energy transfer. However, the p-BCOB:Ir(piq)2acac PHOLED is the best among three hosts with a maximum external quantum efficiency of 7.9% due to the effective charge trapping. This work demonstrates that different host molecular structures have a big effect on the PHOLEDs performance.

Hydrogen peroxide activated quinone methide precursors with enhanced DNA cross-linking capability and cytotoxicity towards cancer cells

Quinone methide (QM) formation induced by endogenously generated H2O2 is attractive for biological and biomedical applications. To overcome current limitations due to low biological activity of H2O2-activated QM precursors, we are introducing herein several new arylboronates with electron donating substituents at different positions of benzene ring and/or different neutral leaving groups. The reaction rate of the arylboronate esters with H2O2 and subsequent bisquinone methides formation and DNA cross-linking was accelerated with the application of Br as a leaving group instead of acetoxy groups. Additionally, a donating group placed meta to the nascent exo-methylene group of the quinone methide greatly improves H2O2-induced DNA interstrand cross-link formation as well as enhances the cellular activity. Multiple donating groups decrease the stability and DNA cross-linking capability, which lead to low cellular activity. A cell-based screen demonstrated that compounds 2a and 5a with a OMe or OH group dramatically inhibited the growth of various tissue-derived cancer cells while normal cells were less affected. Induction of H2AX phosphorylation by these compounds in CLL lymphocytes provide evidence for a correlation between cell death and DNA damage. The compounds presented herein showed potent anticancer activities and selectivity, which represent a novel scaffold for anticancer drug development.

Optical absorption and emission properties of benzene-expanded Janus AT nucleobase analogues: A DFT study

We design benzene-expanded Janus AT bases (J-AT1, J-AT2, BF1 and BF2) and investigate the structural and optical properties of these bases using DFT and TDDFT methods and also consider the effect of water solution and base pairing. The results show that J-AT1 has a nonplanar structure and its amino group is more asymmetric than the other three bases. J-AT1 and BF1 exist intramolecular H-bonds. The Janus AT base pairs exist three intermolecular H-bonds: NH···N has the largest energy, followed by NH···O and CH···O. The Janus AT base pairs retain the strength of H-bonds and maintain the stability of the base pair. The lowest absorption and emission wavelengths of the benzene-expanded Janus AT bases are all assigned to ππ* character arising from HOMO to LUMO transition, and they exhibit redshift due to the increase in effective conjugation length with the introduction of benzene. The excited state assignments in water solution are one-to-one correspondence to those in gas phase. The lowest absorption and emission wavelength of J-AT1 is blueshift, while J-AT2, BF1 and BF2 bases are redshift as compared to those in gas. The TD-B3LYP method predicts that the first excitation wavelengths of Janus AT base pairs are local excitation on the Janus AT base moieties, which is coincident with the result of CAM-B3LYP and M062X functional. Base pair can influence the excitation properties of base monomer. The results obtained from this theoretical investigation confirm that the position of benzene ring significantly influences the structure and optical properties of the Janus AT bases.

Pharmacophore-Based Comparative Molecular Similarity Indices Analysis of CRTh2 Antagonists

Chemoattractant Receptor Homologous molecule expressed on Th2 cells (CRTh2) is a chemoattractant receptor with seven transmembrane helices targeted for inflammatory diseases such as asthma and allergic rhinitis. In this study, pharmacophore based Comparative Molecular Similarity Indices Analysis (CoMSIA) were performed on the series of 2-(2-(benzylthio)-1H-benzo[d]imidazol-1-yl) acetic acids derivatives. Initially, GASP module was used for generation of pharmacophore models using five highly active compounds from the dataset. Among the generated pharmacophores, the best pharmacophore model was selected based on fitness score and was used as template for the alignment of compounds which was used for CoMSIA analysis. The best predictions were obtained utilizing steric, hydrophobic and H-bond acceptor parameters showing a <TEX>$q^2$</TEX>=0.559 and <TEX>$r^2$</TEX>=0.730. 15 test set compounds was used to investigate the predictive ability of the CoMSIA model. Contour maps suggested that presence of bulky substituents and H-bond acceptor atoms at <TEX>$5^{th}$</TEX> position of benzene ring will increase the activity of the compounds. The results obtained from this study will be useful to design more potent CRTh2 antagonists.

Formation of cine‐Substitution Products in the SuzukiMiyaura Cross‐Coupling Reaction Catalyzed by Dinuclear Palladium Complexes

AbstractThe SuzukiMiyaura coupling reaction catalyzed by dinuclear palladium complexes gave cine‐substitution products along with ordinary ipso‐substitution products. In the reaction in (D6)benzene, the ipso position of the cine‐substitution product was highly deuterated. The H/D exchange also occurred in various positions of benzene rings.

Exploring DNA binding properties and biological activities of dihydropyrimidinones derivatives

The effects of substituent modifications for three dihydropyrimidinones derivatives on DNA binding properties were investigated using viscometry in combination with spectroscopy and isothermal titration calorimetry (ITC). The results indicated that substitution in 4 rd position of benzene ring has significant effects on DNA binding mode, affinity and energetics. Electron-donating substitution was favorable for intercalating into DNA bases and had higher DNA binding affinity. However, electron-withdrawing substitution was preferable to bind to DNA in partial intercalation mode with relatively weak DNA binding affinity. Simultaneously, electron-donating substitution could result in more favorable binding enthalpy relative to electron-donating substitution and the parent compound. Antitumor activities of these analogs over BEL-7402 and PC-12 cells were studied to explore the structure activity relationships (SARs), which suggested that electron-donating substitution in 4 rd position of benzene ring could greatly enhance the antitumor activities. However, electron-withdrawing substitution has little effect on the antitumor activity. The present results favor the development of potential drugs related with dihydropyrimidinones derivatives in the treatment of some diseases.

Structures, luminescence and vibrational spectroscopy of europium and terbium nitro- and dinitro-substituted benzoates. Nitro groups as quenchers of Ln3+ luminescence

Abstract The nitro-substituted benzoates Ln(NBenz)3·nH2O, Ln(DNBenz)3·nH2O, Ln(NBenz)3·L·nH2O and Ln(DNBenz)3·L·nH2O (Ln = Eu, Tb; NBenz = 2- and 4-nitrobenzoate anions, DNBenz = 3,5- and 2,5-dinitrobenzoate anions; L = Phen and Bpy) were investigated by methods of luminescence and vibrational Raman and IR spectroscopy. The crystal structures of [Eu(4-NBenz)3·(H2O)2]·0.5H2O and [Eu2(4-NBenz)6·Bpy2·(H2O)2]·2H2O (1) were solved by X-ray diffraction methods. Known structural data for lanthanide nitrobenzoates are analyzed. The influence of NO2 groups located in different positions of benzene ring on the structure of Ln3+ coordination centre and on processes of the excitation energy transfer to Ln3+ ion was studied. The presence of electron-withdrawing nitro groups at aromatic ring of the ligand dramatically decreases Eu3+ and Tb3+ luminescence efficiencies. This fall amounts to factor ∼102 in comparison with europium and terbium benzoates. Low sensitization efficiency of Ln3+ luminescence in nitrobenzoates is caused by a dissipation of the excitation energy through the ligand S n π * excited state corresponding to transition between the NO2 oxygen lone pairs orbital and the π* orbital of nitrobenzoate ligand. A low energy of the ligand T n π * state in comparison with Tb3+ 5D4 state makes for a supplementary reduction of the sensitization of Tb3+ luminescence. In ternary compounds, an interligand energy transfer from the Phen or Bpy molecule to nitrobenzoate anion with following quenching due to the nitrobenzoate non-radiative relaxation is observed.

Rationalization of physicochemical characters and docking of 3-alkoxy-5-phenoxy-N-thiazolyl benzamide analogs toward glucokinase activator activity

Diabetes mellitus is a chronic metabolic disorder involving the dysregulation of glucose metabolism, β-cell dysfunction, and impaired insulin sensitivity. Glucokinase (GK) promotes glycogen synthesis, while it enhances insulin secretion from pancreatic β-cells. In this study, we focused on molecular modeling study of 3-alkoxy-5-phenoxy-N-thiazolyl benzamide analogs with reference to structural requirements. The amalgamated best fit consensus scoring function showed coefficient of determination (0.927), leave-one-out cross-validated squared correlation coefficient (0.865), and external predictivity value (0.763). The binding of 3-alkoxy-5-phenoxy-N-thiazolyl benzamide analogs to glucokinase enzyme was explored with the help of docking. The most stable ligand–enzyme complex of compound TR-2 showed that the NH of the benzamide make key hydrogen bonds with the backbone C=O of Arg63. The phenoxy moiety on the 5th position of benzene ring occupies the hydrophobic space on the allosteric binding site constituted from Met210, Met235, Cys220, and Tyr214. One of the oxygen of methylsulfonyl group forms hydrogen bond with NE2 of Gln98 and phenyl ring and the aromatic ring of Tyr215 are perpendicular to each other, which probably increase potency due to van der Waals interactions.The structural insights gleaned from the study could be usefully employed to design activators with a much more enhanced potency.

The sterically hindered salicylaldimine ligands with their copper(II) metal complexes: Synthesis, spectroscopy, electrochemical and thin-layer spectroelectrochemical features

The synthesis, structure, spectroscopic and electro-spectrochemical properties of sterically constrained Schiff-base ligands ( L n H) ( n = 1, 2, and 3) (L = N-[ m-(methylmercapto)aniline]-3,5-di- t-butylsalicylaldimine, m = 4, 3, and 2 positions, respectively) and their copper(II) complexes [ Cu( L n ) 2] are described. Three new dissymmetric bidentate salicylaldimine ligands containing a donor set of ONNO were prepared by reaction of different primary amine with 3,5-di- t-butyl-2-hydroxybenzaldehyde (3,5-DTB). The copper(II) metal complexes of these ligands were synthesized by treating an methanolic solution of the appropriate ligand with an equimolar amount of Cu(Ac) 2 · H 2O. The ligands and their copper complexes were characterized by FT-IR, UV–Vis, 1H and 13C NMR and elemental analysis methods in addition to magnetic susceptibility, molar conductivity, and spectroelectrochemical techniques. Analytical data reveal that copper(II) metal complexes possess 1:2 metal–ligand ratios. On the basis of molar conductance, the copper(II) metal complexes could be formulated as [ Cu( L n ) 2] due to their non-electrolytic nature in dimethylforamide (DMF). The room temperature magnetic moments of [ Cu( L n ) 2] complexes are in the range of 1.82–1.90 B.M which are typical for mononuclear of Cu(II) compounds with a S = 1/2 spin state. The complexes did not indicate antiferromagnetic coupling of spin at this temperature. Electrochemical and thin-layer spectroelectrochemical studies of the ligands and complexes were comparatively studied in the same experimental conditions. The results revealed that all ligands displayed irreversible reduction processes and the cathodic peak potential values of ( L 3 H) are shifted towards negative potential values compared to those of ( L 1 H) and ( L 2 H). It is attributed to the weak-electron-donating methyl sulfanyl group substituted on the ortho ( m = 2) position of benzene ring. Additionally, all copper complexes showed one quasi-reversible one-electron reduction process in the scan rates of 0.025–0.50 V s −1, which are assigned to simple metal-based one-electron processes; [Cu(2+)(L n ) 2] + e − → [Cu(1+)(L n ) 2] −. The spectral changes corresponding to the ligands and complexes during the applied potential in a thin-layer cell confirmed the ligand and metal-based reduction processes, respectively.

Catalytic Oxidative Cyclocondensation of o‐Aminophenols to 2‐Amino‐3H‐phenoxazin‐3‐ones.

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Catalytic Oxidative Cyclocondensation of o‐Aminophenols to 2‐Amino‐3H‐phenoxazin‐3‐ones

The catalytic oxidative cyclocondensation of the o‐aminophenols 1a–f was investigated. The oxidants used were air/laccase, H2O2/horseradish peroxidase, H2O2/ebselen (3), and TBHP/diphenyl diselenide 4. The products obtained were 2‐amino‐3H‐phenoxazin‐3‐one—questiomycin A, its derivative 2b, and cinnabarinic acid and actinocin (2c,d). Substrates with methyl groups at 4 and 5 positions of benzene ring were converted to different dihydrophenoxazinones 2g,h. Compounds having chlorine atoms at the same positions underwent oxidation to planar phenoxa-zinones 2e,f with elimination of one hydrochloride molecule.

Selective Protection of 1,4,8,11-Tetraazacyclotetradecane (Cyclam) in Position 1,4 with the Phosphonothioyl Group and Synthesis of a Cyclam-1,4-bis(methylphosphonic Acid). Crystal Structures of Several Cyclic Phosphonothioamides

A new cyclam-based ligand, 1,4,8,11-tetraazacyclotetradecane-1,4-bis(methylphosphonic acid) (1,4-H4te2p), was synthesized. Cyclam was protected by the reaction with PhP(S)Cl2 to form exclusively five-membered cyclic phenylphosphonothioic diamide 2 in a moderate yield. The solid-state structures of 2 and several by-products were determined. Compound 2 was isolated as two stable conformers differing in a mutual position of benzene ring and sulfur atom with respect to the cyclam ring. Compound 2 was used for the synthesis of 1,4-dibenzylcyclam. However, the deprotection of the thiophosphoryl-protected bis(methylphosphonate diester) with aqueous HCl under non-optimized conditions led to a mixture of cyclam derivatives differently substituted with methylphosphonic acid groups. The crystal structures of the target product, 1,4-H4te2p, and also 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetrakis(methylphosphonic acid) (H8tetp) were determined. A similar reaction with cyclen (1,4,7,10-tetraazacyclododecane) led only to hardly purifiable mixtures.