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In this study, the transition metal chelates of Mn(II), Ni(II) and Cu(II) with Schiff base were synthesized and characterized. The elemental analysis data showed that, the isolated chelates are in 1:1 [M:L] ratio. The molar conductance values revealed that the chelates are none electrolyte in nature. The results of magnetic moment measurements demonstrated that, the chelates of Mn(II) and Cu(II) have unpaired electrons and chelates of Ni(II) is diamagnetic. The infrared spectral data displayed the main coordination sites of (2E, 3E)-3-((2-aminophenyl)imino)butan-2-one oxime towards Mn(II), Ni(II) and Cu(II) ions. The electronic spectrum results of the Schiff base ligand and its chelates suggest that the Mn(II) and Cu(II) chelates have octahedral structure and Ni(II) chelate is square planar.

Baijiu is a distilled liquor of great importance in the food industry. Various aroma types, brands, and grades of Baijiu have filled the market; thus, discrimination for quality control is required. Herein, we constructed a novel colorimetric sensor array based on the redox reaction between silver nitrate and o-phenylenediamine or its derivatives for the discrimination of carbonyl flavor compounds (CFCs) and Baijius. The specific colored products were changed by CFCs depending on the influence of silver nanoparticle aggregation and chemical reactions. The array was used to qualitatively and quantitatively identify 21 CFCs with fast response (14 min), wide linear range (0.025-25 mmol/L), and low detection limits (60 μmol/L, 29 nmol/L for carboxylic acids). Finally, the array was successfully applied to the discrimination of 56 Baijius. The method proposed in this study is simple, fast, reliable, and has good application potential for the visual determination of Chinese Baijiu.

In the present study, 2-Arylbenzimidazoline generated in situ from reaction of aromatic aldehydes and o-phenylenediamine used as biomimetic reductive agents for reductive alkylation of 2-hydroxy-4H-benzo[4,5]thiazolo[3,2-a]pyrimidin-4-one for synthesis of novel 3-benzyl-2-hydroxy-4H-benzo[4,5]thiazolo[3,2-a]pyrimidin-4-ones is described. The main benefits of this protocol include simplicity, reaction mildness, high yield, easy work up, and simple purification. The molecular structures were characterized by IR spectrophotometry, mass spectrometry, NMR spectroscopy, and elemental analysis.

Reported herein is an unprecedented and sequential three-component synthetic strategy for the preparation of polycyclic N-heterocyclic compounds. This synthetic protocol enabled the preparation of a series of novel nitrogen-containing pentacyclic compound under convenient conditions in excellent yields and short reaction time. The synthesized products were characterized by IR, 1H NMR, 13C NMR and mass spectra. Furthermore, the definitive structure of target compounds was confirmed by X-ray analysis.

In this work, a poly-orthophenylene diamine substrate is decorated with gold nanoparticles (GNPs) and then with single-stranded DNA (ss-DNA) aptamer immobilized on the surface of a pencil graphite electrode (PGE) for the detection and determination of plasma insulin. In this procedure, a polymer layer is formed on the surface of the graphite electrode using anodic oxidation of orthophenylene diamine monomers. The parameters affecting the biosensor sensitivity including the potential applied to form the polymer layer, incubation time, concentration of immobilized ss-DNA, and the presence of MgCl 2 (as salt) are evaluated. Electrochemical impedance spectroscopy and cyclic voltammetry are then used to characterize the biosensor. The biosensor is employed under optimal conditions to obtain figures of merit, which reveal a linear range and a limit of detection of 1.0–1000.0 nmol L −1 and 0.27 nmol L −1 , respectively. Finally, the aptasensor is employed for the determination of insulin in real plasma and urine samples to verify its performance and effectiveness.

Amine-functionalized Fe3O4@C nanoparticles with an average diameter of 266nm have been successfully synthesized by a solvothermal reduction method. The structure, morphology and properties of the Fe3O4@C nanoparticles were investigated through different analytical tools. Due to the magnetic nature and the presence of amine-functionalized groups, the as-prepared Fe3O4@C nanoparticles were employed as magnetic carriers for laccase immobilization. The results indicated that the loading of laccase onto the amine-functionalized Fe3O4@C nanoparticles was approximately 195mg/g. In comparison with free laccase, the pH, operational and storage stabilities of the immobilized laccase were significantly improved. After 10 consecutive operations, the immobilized laccase retained above 60% residual activity. The removal rates of o-phenylenediamine (OPD) by immobilized laccase were 88%, which were much higher than that of free laccase (50%). It hoped that the amine-functionalized Fe3O4@C nanoparticles may find an application in biotechnology and catalysis.

In this work, a novel and simple fluorescence method for detection of uric acid (UA) based on NaYF4:Yb(3+), Tm(3+) upconversion nanoparticles (UCNPs) is developed. The proposed method is based on the fact that uricase can oxidize uric acid to allantoin and hydrogen peroxide, which, on its turn, can oxidize o-phenylenediamine (OPD) to the oxidized OPD (oxOPD). The fluorescence of UCNPs can be significantly quenched by oxOPD through inner filter effects (IFE). Under the optimized conditions, the UA concentration was proportional to the changes in fluorescence intensity of UCNPs. A linear response was obtained over the concentration range from 20 to 850μΜ with the low detection limit of 6.7μΜ for uric acid. More importantly, this method has the potential to detect uric acid in human serum samples, suggesting the nanosensor can be used in a complex biological sample matrix.

In this study, we report a novel magnetic biomimetic nanozyme (Fe3O4@Cu/GMP (guanosine 5′-monophosphate)) with high laccase-like activity, which could oxidize toxic o-phenylenediamine (OPD) and remove phenolic compounds. The magnetic laccase-like nanozyme was readily obtained via complexed Cu2+ and GMP that grew on the surface of magnetic Fe3O4 nanoparticles. The prepared Fe3O4@Cu/GMP catalyst could be magnetically recycled for at least five cycles while still retaining above 70% activity. As a laccase mimic, Fe3O4@Cu/GMP had more activity and robust stability than natural laccase for the oxidization of OPD. Fe3O4@Cu/GMP retained about 90% residual activity at 90°C and showed little change at pH 3–9, and the nanozyme kept its excellent activity after long-term storage. Meanwhile, Fe3O4@Cu/GMP had better activity for removing phenolic compounds, and the removal of naphthol was more than 95%. Consequently, the proposed Fe3O4@Cu/GMP nanozyme shows potential for use as a robust catalyst for applications in environmental remediation.

The acid-promoted three-component reaction of o-aminophenol or 2-aminoethanol with dialkyl acetylenedicarboxylate and 3-phenacylideneoxindolines in refluxing acetonitrile afforded functionalized oxindolinyl-substituted benzo[b]pyrrolo[1,2-d][1,4]oxazine or pyrrolo-[2,1-c][1,4]oxazine derivatives in good yields. However, using o-phenylenediamine only resulted in oxindolinyl-substituted 3,4-dihydroquinoxaline derivatives.

A simple and efficient protocol for preparing benzimidazoles via Fe(NO3)3 · 9H2O-catalyzed aerobic oxidation reaction of imine derivatives with o-phenylenediamine. This process uses air as an economical and green oxidant, tolerates a wide range of substrates, and affords the targeted benzimidazoles in moderate to excellent yields.

Both 1,5-benzodiazepine and quinoxaline derivatives are important heterocycles in pharmaceuticals. We describe an efficient and clean method for the synthesis of 1,5-benzodiazepines from o-phenylenediamine and ketones catalyzed by sodium tetrachloroaurate(III) dihydrate under mild conditions. The catalyst was shown to be equally effective for the synthesis of quinoxalines from o-phenylenediamine and alpha-bromo ketones under the similar reaction conditions. This method produced good yields.

Microencapsulation is used here as a new technique to immobilize enzymes in a microreactor coupled off-line to capillary electrophoresis (CE), allowing the determination of enzymatic reaction products. The redox enzyme laccase was encapsulated using the method of interfacial cross-linking of poly(ethyleneimine) (PEI). The 50 microm diameter capsules were slurry packed from a suspension into a capillary-sized reactor made easily and quickly from a short length of 530 microm diameter fused-silica tubing. The volume of the bed of laccase microcapsules in the microreactor was in the order of 1.1 microL through which 50 microL of the substrate o-phenylenediamine (OPD) was flowed. The oxidation product 2,3-diaminophenazine (DAP) and the remaining OPD were quantified by CE in a pH 2.5 phosphate buffer. Peak migration time reproducibility was in the order of 0.4% RSD and peak area reproducibility was less than 1.7% RSD within the same day. Using the OPD peak area calibration curve, a conversion efficiency of 48% was achieved for a 2-min oxidation reaction in the microreactor.

Methylglyoxal (MG), a reactive metabolic byproduct and a precursor of advanced glycation endproducts (AGEs), is elevated in diabetes. In the body MG is free or reversibly or irreversibly bound (mostly with proteins). Variable plasma MG values have been reported. MG is commonly measured using high performance liquid chromatography. We tested several protocols on different biological samples, which resulted in significant differences in MG values measured in a given sample. The different values do not appear due to the release and detection of bound MG under assay conditions. Protocols that provide consistent values of MG in biological samples are recommended.

Review: [applications of catechol, o-aminophenol and o-phenylenediamine based redox-active ligands for the chemical reactivity and catalysis; 96 refs.

The reactions of 4-pyrone-2-carboxylic acid derivatives (I), (V), (X), and (XIII) with o-phenylenediamine (II) or 2-aminophenol (VIII) are described.

Solvent-free oxidative synthesis of benzimidazoles from arylmethylamines and o-phenylenediamine has been achieved under catalyst-free conditions. This reaction can use tert-butyl hydroperoxide (TBHP) as the oxidant, and a wide variety of derivatives were obtained in good yields. The reaction mechanism was proposed and this method provides a direct and practical approach for the preparation of substituted benzimidazoles.

The reactions of epoxy derivatives of internal perfluoroolefins with o-phenylenediamine and 2-aminophenol in dioxane gave 23–67% of the corresponding 2,3-bis(perfluoroalkyl)quinoxalines and 2,3-bis(perfluoroalkyl)-2H-1,4-benzoxazin-2-ols, respectively. When N,N-dimethylacetamide was used as a solvent, the main reaction pathway was anionic isomerization of epoxides into ketones which were then converted into 2-perfluoroalkylbenzimidazoles (in the reactions with o-phenylenediamine) or 2-hydroxy-N-perfluoroalkanoylanilines (in the reactions with 2-aminophenol). The reaction of 3,4-epoxydodecafluorohexane with 2-aminophenol in N,N-dimethylacetamide was accompanied by unusual cyclization to afford 2-pentafluoropropanoyl-2-pentafluoroethyl-1,3-benzoxazolidine.

A convenient, solvent‐free, green approach is described for the synthesis of novel 1,5‐benzodiazepines by the reaction of ethylacetoacetate, aldehyde, and o‐phenylenediamine without any catalyst at pH 7.

The title reaction affords enedioates (III) which easily cyclize into new derivatives of pyrido[1,2-a]quinoxaline system (IV).

The use of molecular iodine as the catalyst for a one-pot synthesis of quinoxaline derivatives at room temperature is reported.

Methemoglobin (metHb) was used as a mimetic enzyme for peroxidase to catalyze the oxidation reaction of o-phenylenediamine (OPDA) with H2O2 functioning as an oxidant. A reaction intermediate was obtained in two-phase aqueous-organic system and an absorption peak at 710 nm was confirmed to be that of the intermediate in relation to OPDA. The isolated product and intermediate were characterized by UV-V is and IR spectrophotometry and HPLC-tandem mass spectrometry. The results showed that the product is 2,3-diaminophenazine, the molecular mass of the intermediate is 212 daltons, and a conceivable structure of the intermediate is suggested. Combining the catalyzed reaction mechanism of peroxidase and our experimental results, a conceivable oxidation reaction mechanism of OPDA and H2O2 using metHb as catalyst is proposed.

The interaction of arylbis(5,5-dimethylcyclohexane-1,3-dion-2-yl)methanes with o-phenylenediamine and o-aminophenol leads to the preparation of 3,3-dimethyl-11-aryl-2,3,4,5,10,11-hexahydrobenzo[b,e]-1,4-diazepin-1-ones and 3,3,6,6-tetramethyl-9-aryl-10-(2-hydroxyphenyl)-2,4,5,7,9-decahydroacridine-1,8-diones respectively. A one-pot method is proposed for the synthesis of derivatives of hexahydrodibenzo[b,e]-1,4-diazepin-1-ones. The structure of the first member of this series was confirmed by X-ray diffraction analysis.

An easy and convenient synthetic procedure for the preparation of benzodiazepines by coupling microwaves with the solvent technique have been elaborated.

A study was carried out of Cu adsorption and desorption processes in red soil as affected by o -phenylenediamine ( o -PD) in the range 0–80 mg/l. The results indicated that the presence of o -PD enhanced Cu adsorption in red soil in weakly acid media, meanwhile, desorption percentage of Cu from soil, extracted by 1.0 M MgCl 2 , also increased when Cu adsorption in soil occurred in the presence of o -PD. The response of paddy rice to Cu in red soil shows that Cu toxicity was mitigated in the presence of o -PD and that the Cu concentration in rice straw decreased with increasing concentration of o -PD from 0 to 4.0 mmol/kg in soil. The fractions of background Cu in soil did not change noticeably in the presence of o -PD, whereas the effect of o -PD on the fractions of added Cu was significant. It was found that the exchangeable and carbonate bound Cu fractions decreased and the fraction of Cu bound to Fe–Mn oxides and organic matter increased with increasing o -PD concentration in soil when Cu was added at the same rate. Copper concentration in rice straw was significantly correlated with exchangeable Cu ( r =0.961) and carbonate bound Cu ( r =0.959) in soil. This result implicates that the behavior of Cu in soil is likely to be affected by organic pollutants containing amino groups.

A regioselective way to synthesize 2-thiomethyl substituted isomers of 1,5-benzodiazepines is presented.

The title reaction results in the formation of pyrazolyl-benzimidazoles (III) or benzopyrroloimidazolones (IV) depending on the reaction conditions.

A method for determination of oxidation of phenolic compounds by intact wheat seedlings using o-phenylenediamine (OPD) was developed. The reaction is initiated by the addition of oxalic acid to the incubation medium. It is suggested that an endogenous peroxidase and hydrogen peroxide formed during oxidation of oxalic acid by endogenous oxalate oxidase are involved in OPD oxidation. Treatment of plants with chitooligosaccharides (1-10 mg/liter) with acetylation degree of 65% and molecular masses of 5-10 kD significantly activated OPD oxidation by wheat seedlings.

We developed a novel, cost-effective, and automated assay for ascorbic acid (AsA) in serum using a COBAS MIRA S analyzer (Roche Diagnostic System). Our method has a wide dynamic range and covers AsA concentrations from well below the lower reference interval to well above it. AsA is oxidized by 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxy, free radical (TEMPO) to dehydroascorbic acid (DAsA). The latter condenses with o-phenylenediamine (OPDA) to form a quinoxaline derivative that absorbs light at 340 nm. The change in absorbance at 340 nm is proportional to the concentration of AsA in the specimen. The automated system permitted the assay of 65 specimens per hour at a cost of approximately US$ 0.01 per specimen for reagents. The assay can be applied directly to serum specimens (direct method) and also to sera with a prior deproteinization step with metaphosphoric acid. The detection limit for the direct serum assays is 0.8 vs. 0.4 mg/l with the deproteinization method. The recovery of AsA from a supplemented serum pool was of >95% for both procedures. We used four distinct methods on 66 patients sera. The direct method for AsA correlated well with an HPLC method (r=0.964, P

Perfluoro(2,3-epoxy-2-methylpentane) reacted with o-phenylenediamine and ethylenediamine via cleavage of the C-C bond to produce 2,2,3,3,3-pentafluoro-N-[2-(2,2,2-trifluoro-1-trifluoromethylethylamino)-phenyl]propanamide and 2,2,3,3,3-pentafluoro-N-[2-(2,2,2-trifluoro-1-trifluoromethylethylamino)ethyl]-propanamide, respectively. Presumably, these compounds are formed as a result of rearrangement of intermediate ketone generated by intramolecular haloform-type reaction. According to the NMR and X-ray diffraction data, 2,2,3,3,3-pentafluoro-N-[2-(2,2,2-trifluoro-1-trifluoromethylethylamino)phenyl]propanamide in crystal exists as Z conformer with respect to the amide C-N bond.

A method is presented for the synthesis of 3-(2-oxo-1,2-dihydro-3H-indol-3-ylidene)-1,4-dihydroquinoxalin-2-one and 2-(2-oxo-1,2-dihydro-3H-indol-3-ylidene)-2H-1,4-benzoxazin-3(4H)-one by the reaction of ethyl 2-oxoindoline-2-glyoxylate with o-aminophenol and o-phenylenediamine. Proposed reaction mechanisms are presented.

Benzylic oxidation of pinopyridine (I) gives keto derivative (II) which yields (8R)-amino derivatives (VI) on reductive amination with anisidines.

Chiral 2-substituted-1,5-benzodiazepine derivatives were synthesized for the first time from an enantioselective domino reaction involving o-phenylenediamine and 2′-hydroxychalcones. The titanium complex formed from chiral ligand 1a derived from (S)-BINOL and L-prolineamide promoted the reaction and gave the products in good yields with up to 82 % ee.

A novel way of synthesizing quinoxalines efficiently through cyclization of o-phenylenediamine and terminal alkyne by Cu(II) and bases is developed. This reaction proceeds smoothly to give the products in moderate to good yields.

A simple, environmental-friendly, and practical method for the synthesis of benzodiazepine derivatives through a reaction of substituted o-phenylenediamines with alkyl propiolates has been developed. The reactions generated the 1,5-benzodiazepines in good to excellent yields in the presence of catalytic amount of In(OTf)3 under solvent-free reaction conditions.

The electrochemical biosensors based on poly(o-phenylenediamine) (PoPD) and acetylcholinesterase (AChE) and choline oxidase (ChO) enzymes were fabricated on carbon fibre (CF) substrate. The electropolymerized PoPD was used to reduce the interfering substances. The electrode assembly was completed by depositing functionalized carbon nano tubes (FCNTs) and Nafion (Naf). Amperometric detection of acetylcholine (ACh) and choline (Ch) were realized at an applied potential of +750 mV vs Ag/AgCl (saturated KCl). At pH 7.4, the final assembly, Naf-FCNTs/AChE-ChO((10:1))/PoPD/CF(Elip), was observed to have high sensitivity towards Ch (6.3±0.3 μA mM(-1)) and ACh (5.8±0.3 μA mM(-1)), linear range for Ch (K(M)=0.52±0.03 mM) and ACh (K(M)=0.59±0.07 mM), and for Ch the highest ascorbic acid blocking capacity (97.2±2 1mM AA). It had a response time of5s and with 0.045 μM limit of detection. Studies on different ratio (ACh/Ch) revealed that 10:1, gave best overall response.

Advantages of the method are high conversion, short reaction time and solvent-free conditions.

Dicarbonyl sugars were separated by capillary electrophoresis as o-phenylenediamine derivatives (quinoxalines). Tetrabutylammonium bromide was used as a modifier; n-arabino-2-hexosulose (n-glucosone), D-lyxo-2-hexostdose (D-gdaCtOSOnC), 7-deoxy-L-galacto-2-hexosulose and 5-hydroxy-2,3dioxohexanal served as standards. The separation procedure was optimized with respect to pH, buffer and solute concentrations. In most instances optimum separations were obtained in 75 mM borate buffer (pH 11.0); 0.04 mg/ml was found to be the optimum sample concentration. The detection limit was ca. 0.1 pmol. Analyses of a mixture of fermentation products or Maillard reaction products show the applicability of the method.

The desired ring system (III) can be prepared at best under microwave irradiation in the presence of o-phenylenediamine.

Reaction of 1,2,3,4-tetrahydroisoquinoline enaminoamides with oxalyl chloride gives 2,3-dioxpyrrolo[2,1-a]isoquinolines which react with o-phenylenediamine to give spiro benzimidazolines or condensed quinoxalines, depending on the conditions used.