A novel reaction between benzothiazoles and diaroylacetylenes in the presence of Meldrum’s acid: ring expansion of benzothiazoles to functionalized 1,4-benzothiazines

A novel and efficient ring expansion of benzothiazoles to functionalized 1,4-benzothiazines is described. The reactive 1:1 zwitterionic intermediates formed by addition of benzothiazoles to diaroylacetylenes were trapped with Meldrum’s acid under mild reaction conditions to produce 2-[2-hydroxy-2-aryl-2H-1,4-benzothiazin-3(4H)-yliden]-1-aryl-1-ethanones in excellent yields.     

Synthesis and biological activity of Magnesium(II) complexes of heptaaza Schiff base macrocyclic ligands; 1H and 13C chemical shifts computed by the GIAO-DFT and CSGT-DFT methodologies

Two new pendant armed Schiff base macrocyclic complexes, [MgL¹](ClO₄)₂ (1), and [MgL²](ClO₄)₂ (2), have been prepared via cyclocondensation of 2,6-diformylpyridine and 2,6-diacetylpyridine with two hexadentate hexaamines, ten and tmen, in the presence of Mg(II) ion. The ligands are 15-membered pentaaza macrocycles having two 2-aminoethyl pendant arms. The newly prepared complexes are investigated by IR, ¹H NMR, ¹³C{¹H} NMR, DEPT(135), COSY(H, H) and HMQC spectroscopic methods. The antimicrobial screening of newly prepared complexes, 1 and 2, as well as previously prepared similar complexes, [MgL³](ClO₄)₂ (3) and [MgL⁴](ClO₄)₂ (4), against Escherichia coli, Staphylococcus aureus and candidia albicans showed that the macrocyclic complexes of Mg(II) containing 15-membered pentaaza ring (1, 2 and 3) have no activity. Where as the compound 4, which contain 16-membered pentaaza ring, had remarkable inhibition zone on the culture of S. aureus and E. coli as compared with standard drugs. The ¹H and ¹³C chemical shieldings of gas phase complexes were also studied by the gauge independent atomic orbital (GIAO) and continuous set of gauge transformations (CSGT) methods at the level of density functional theory (DFT). The computed ¹³C chemical shifts are in reasonably good agreement with the experimental data.     

Testing catalytic activity of ruthenium(III) acetylacetonate in the presence of trialkylphosphite or trialkylphosphine in hydrogen generation from the hydrolysis of sodium borohydride

Catalytic activity of Ru(acac)₃ in the presence of different phosphorus compounds (P(OMe)₃, P(OPh)₃, PPh₃ and dppe) was investigated for the first time in the hydrolysis of NaBH₄. Phosphorus compound, usually known as poison in catalysis, is involved in the formation of a species which has higher catalytic activity in comparison with Ru(acac)₃ alone. Varying the phosphorus compound affects the catalytic activity and lifetime of the catalyst as well as the kinetics and the activation parameters of the hydrolysis of NaBH₄. For all of the phosphorus compounds, the hydrogen generation was found to be zero-order with respect to the substrate concentration and first-order regarding the catalyst concentration. The catalyst system with P(OMe)₃ shows the highest catalytic activity and provides the largest total turnover number (TTON = 20,700 over 72 h) in the hydrolysis of NaBH₄. The highest activation energy and enthalpy values were obtained for the catalyst with dppe (E_a = 59 ± 2, ΔH^# = 60 ± 2 kJ/mol) while the lowest values were found for the catalyst system with PPh₃ (E_a = 46 ± 2, ΔH^# = 43 ± 1 kJ/mol).     

Comparison of Volatile Organic Compounds of Thymus Vulgaris Using Hydrodistillation and Headspace Solid Phase Microextraction Gas Chromatography Mass Spectrometry

Essential oil of aerial parts of Tymus vulgaris L. from Babaaman montains of Iran were isolated by hydrodistillation with an average oil yield 1.9 w/w%. The components of the oil were identified by gas chromatography mass spectrometry. On a separate experiments the compositions of volatile emission of the plant were studied by headspace solid phase microextraction and gas chromatography mass spectrometry. The tempratures used during the sample preparation were 25°C and 50°C. In order to determine the effect of solvent (water) on the separation, the experiments were done in the presence and absence of distilled water in the extraction vial at the tempratures mentioned above. Ten majour components were obtained in four different experimental headspace solid phase microextraction conditions and the hydrodistillation methods from the plant. Thymol was found to be the most abundant costituent (27.2–73.09%), follwoed by p‐cymene (6.86–31.76%), γ‐terpinene (1.02–9.26%), myrcene (0.05–8.84%), α‐pinene (0.25–6.63%), caryophyllene (3.09–5.56%), thymol methyl ether (0.99–2.97%), thymolacetate (0.11–2.05%), carvacrol (0.49–1.70%) and α‐cadinol (0.38–1.10%).     

A multi-component synthesis of 3-aryl-1-(arylmethylideneamino)pyrrolidine-2,5-diones

A multi-component synthesis of 3-aryl-1-(arylmethylideneamino)pyrrolidine-2,5-diones is described. A mixture of N-isocyaniminotriphenylphosphorane, an aldehyde, and Meldrum's acid undergo a 1:2:1 addition reaction under mild conditions to afford the title compounds in good to excellent yields.     

Unique substituted 3-oxo-1,2,3,4-tetrahydropyrazino[1,2-a]benzimidazole-1-carboxamides generated by Ugi 3CC using bifunctional starting material

2-(2-Formyl-1H-benzimidazol-1-yl)acetic acid, as a bifunctional formyl-acid was prepared in four steps. This compound underwent one-pot reaction with primary amines, and alkyl isocyanides under Ugi conditions. A series of novel 3-oxo-1,2,3,4-tetrahydropyrazino[1,2-a]benzimidazole-1-carboxamides were obtained in moderate to excellent yields.     

Synthesis and characterization of organo-soluble poly(amide-imide)s based on 1,2-bis[4-(trimellitimido)phenoxy]ethane and aromatic diamines

<正>New organo-soluble poly(amide-imide)s(PAIs) 8a-8f were prepared from newly synthesized 1,2-bis[4,4'-(trimellitimido) phenoxy]ethane 6 via direct polycondensation with various aromatic diamines.The diacid 6 was synthesized by the condensation reaction of 12-bis[4-atninophenoxy]ethane 4 with trimellitic anhydride 5 in acetic acid.All polymers were obtained in quantitative high yields with inherent viscosities of 0.48-0.61 dL/g.All of these polymers were highly soluble in organic solvents such as,N-methyl-2-pyrrolidone(NMP),dimethylformamide(DMF),N,N'-dimethylacetamide (DMAc) and dimethylsulfoxide(DMSO) at room temperature and were fully characterized by means of NMR spectroscopy, FTIR spectroscopy,elemental analyses,inherent viscosity,solubility test,specific rotation,differential scanning calorimetry (DSC) and thermogravimetric analysis(TGA).     

Syngas production by combined carbon dioxide reforming and partial oxidation of methane over Ni/α-Al2O3 catalysts

Ni/α-Al2O3 catalysts were found to be active in the temperature range 600~900 ℃ for both CO2 reforming and partial oxidation of methane. The effects of Ni loading, reaction temperature and feed gas ratio for the combination of CO2 reforming and partial oxidation of CH4 over Ni/α-Al2O3 were investigated. Catalysts of xwt%Ni/α-Al2O3 (x = 2.5, 5, 8 and 12) were prepared by wet impregnating the calcined support with a solution of nickel nitrate. XRD patterns and activity tests have verified that the 5wt%Ni/α-Al2O3 was the most active catalyst, as compared with the other prepared catalyst samples. An increase of the Ni loading to more than 5 wt% led to a reduction in the Ni dispersion. In addition, by combining the endothermic carbon dioxide reforming reaction with the exothermic partial oxidation reaction, the loss of catalyst activity with time on stream was reduced with the amount of oxygen added to the feed.     

Preparation and characterization of polyurethane electrical insulating coatings derived from novel soybean oil‐based polyol

As a viable alternative to the petrochemical polyols in polyurethanes (PUs), a new soybean oil‐based polyol (PSBO) with high functionality of hydroxyl groups and built‐in (preformed) urethane bonds was introduced. At first, a facile and improved method was developed for the transformation of epoxidized soybean oil (ESBO) to carbonated soybean oil (CSBO). Then ring‐opening reaction of carbonated oil with ethanolamine (ETA) led to the polyol. After characterization by conventional spectroscopic and analytical methods, PSBO was used for the formulation of novel one‐pack PU electroinsulating wire enamels. Tunable mechanical, thermal, and electrical properties for the final PUs were achieved by replacing 10 wt% of PSBO with poly(propylene glycol) (PPG) at different number average molecular weights of 725, 1000, 2000, 4000. Investigation of the results showed that these soy‐based PUs offer excellent thermal and electrical insulating properties. Copyright © 2009 John Wiley & Sons, Ltd.