Showing papers in "Monatshefte Fur Chemie in 2006"
TL;DR: In this paper, from extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium H+ (aq) + NaL+ (nb) = HL+(nb)+ Na+(aq) taking place in the two-phase water-nitrobenzene system (L = valinomycin, aq = aqueous phase, nb = nitrobenzinene phase) was evaluated as log Kex (H+, NaL+) = −1.1 ± 0.1.
Abstract: Summary.From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium H+ (aq) + NaL+ (nb) = HL+ (nb) + Na+ (aq) taking place in the two-phase water-nitrobenzene system (L = valinomycin, aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex (H+, NaL+) = −1.1 ± 0.1. Further, the stability constant of the valinomycin-proton complex in nitrobenzene saturated with water was calculated as log βnb(HL+) = 5.3 ± 0.1. Finally, the stability constants of complexes of some univalent cations with valinomycin were summarized and discussed.
114 citations
TL;DR: In this paper, the major advances made on titanium-oxo clusters chemistry and their derived hybrid materials are described and the main synthesis procedures, the cluster structures presented in literature, and the relation between the titanium-oxide clusters condensation degree and poisoning ratio are discussed.
Abstract: This review describes the major advances made on titanium-oxo clusters chemistry and their derived hybrid materials. The main synthesis procedures, the cluster structures presented in literature, and the relation between the titanium-oxo clusters condensation degree and poisoning ratio are discussed. The tuned organo-functionalisation of the titanium-oxo based nanobuilding blocks allows to develop a LEGO-like chemistry, able to direct the assembling of a large variety of structurally well defined complex hybrid architectures.
110 citations
TL;DR: In this article, the synthesis of crosslinkable small and large organic molecules having OLED properties is presented. And three strategies for the construction of multilayer and multicolour devices are described, where small, well-defined OLED molecules are functionalized with oxetanes as crosslinker.
Abstract: Synthesis of crosslinkable small and large organic molecules having OLED properties will be presented. Three strategies for the construction of multilayer devices will be described. In the first case small, well-defined OLED-molecules are functionalized with oxetanes as crosslinker. The second case deals with polymers having OLED active units in the main chain and pendant crosslinkers and finally it was shown that styrene polymers with pendant OLED functions and crosslinkers can be applied for the construction of such multilayer and multicolour devices.
98 citations
TL;DR: In this article, a method of synthesis of 2-substituted benzimidazoles by means of the heterogeneous catalysis of synthetic and natural zeolites in the reaction of 1,2-diaminobenzene with acid chlorides is described.
Abstract: A superior method of synthesis of 2-substituted benzimidazoles by means of the heterogeneous catalysis of synthetic and natural zeolites in the reaction of 1,2-diaminobenzene with acid chlorides is described.
81 citations
TL;DR: This is a simple, one-pot, high yielding technique using cheap, non-toxic iodine in catalytic amounts for the synthesis of 2,4,5-triarylimidazoles in excellent yields via condensation of benzoin, ammonium acetate, and aromatic aldehydes.
Abstract: Elemental iodine is used as an efficient catalyst for the synthesis of 2,4,5-triarylimidazoles in excellent yields via condensation of benzoin, ammonium acetate, and aromatic aldehydes This is a simple, one-pot, high yielding technique using cheap, non-toxic iodine in catalytic amounts
69 citations
TL;DR: Hantzsch 1,4-dihydropyridine compounds were synthesized efficiently in high yields at room temperature within short times in 1,1,3,3-N,N, N′,N′-tetramethylguanidinium trifluoroacetate as ionic liquid using ultrasound irradiation as mentioned in this paper.
Abstract: Hantzsch 1,4-dihydropyridine compounds were synthesized efficiently in high yields at room temperature within short times in 1,1,3,3-N,N,N′,N′-tetramethylguanidinium trifluoroacetate as ionic liquid using ultrasound irradiation. The ionic liquid can be recovered conveniently and reused efficiently.
67 citations
TL;DR: In this article, a new kind of barrier coating material, namely inorganic-organic polymers, is proposed to obtain excellent barrier properties against oxygen, water vapor, and flavor permeation.
Abstract: With a new kind of barrier coating material, namely inorganic–organic polymers, it is possible to obtain excellent barrier properties against oxygen, water vapor, and flavor permeation. These hybrid polymers can be synthesized by the sol–gel technique. If extremely low permeation values are needed, the combination of hybrid polymer coatings with thin inorganic oxidic layers (SiO
x
, AlO
x
) is very effective and leads to permeation values for oxygen and water vapor below 10−3 cm3/m2 · d · bar or g/m2 · d. These passive barrier layers can be further improved by the combination with active oxygen barrier layers which have been developed for the food packaging industry. This approach makes these multilayer laminates promising candidates for special applications in the food packaging industry as well as for sophisticated applications in technical areas: the encapsulation of sensitive organic devices like solar cells, organic light emitting diodes, or polymer electronic systems.
55 citations
TL;DR: The use of carbon dioxide as a cheap and harmless reagent for the synthesis of organic carbamates in the gaseous or supercritical state, or in an electrochemical process, was discussed in this article.
Abstract: Organic carbamates classically have been synthesized using harmful and toxic reagents like phosgene, its derivatives, and carbon monoxide. Recently, carbon dioxide was used as a cheap and harmless reagent for the synthesis of organic carbamates in the gaseous or supercritical state, or in an electrochemical process, or organic carbonates as sources of carbon dioxide as an alternative to the harmful reagents. The present review will deal with the extensive use of carbon dioxide in the synthesis of organic carbamates.
52 citations
TL;DR: In this paper, the conversion of alicyclic and aliphatic carbonyl compounds as well as aromatic aldehydes into the corresponding oximes (up to quantitative yields) was achieved by simply grinding these reactants, hydroxylamine hydrochloride and sodium hydroxide without solvent.
Abstract: The conversion of alicyclic and aliphatic carbonyl compounds as well as aromatic aldehydes into the corresponding oximes (up to quantitative yields) was achieved by simply grinding these reactants, hydroxylamine hydrochloride and sodium hydroxide without solvent. However, this procedure was unsuccessful in the case of aromatic ketones. In this case it was necessary to add silica gel as a catalyst.
50 citations
TL;DR: In this article, the authors present a review of analytical evaluation procedures used to study hybrid materials using X-ray scattering in sol-gel chemistry, which is one of the most important techniques for the characterization of inorganic-organic hybrid materials.
Abstract: With the improved control of the nanostructure and the handling of multicomponent systems in sol–gel chemistry, the research interest in this field increased significantly in the past decade. For the characterization of the nanostructure of inorganic–organic hybrid materials, small-angle X-ray scattering has proven to be one of the most important techniques. By using X-rays from synchrotron radiation sources, even the structural development during processing can be followed in-situ. This short note reviews some analytical evaluation procedures used to study hybrid materials. While numerical simulation tools are nowadays available to obtain detailed fits of scattering curves, the use of analytical models is still very useful if the evaluation and interpretation of the obtained parameters is straightforward.
41 citations
TL;DR: In this paper, the Fridedlander synthesis of quinolines through condensation reaction of a 2-aminoaryl ketone with an activated α-CH acid compound under solvent-free conditions in high yields at 100°C.
Abstract: Silica sulfuric acid as an inexpensive and recyclable solid acid efficiently catalyzes the Fridedlander synthesis of quinolines through a condensation reaction of a 2-aminoaryl ketone with an activated α-CH acid compound under solvent-free conditions in high yields at 100°C.
TL;DR: A synthesis of 3-(4methoxycarbonyl-2,6-dinitrophenyl)indole, its 2,6diamino analog, and 3-(2-amino-4-trifluoromethyl-6-nitrophensyl)-indole is described in this paper.
Abstract: A synthesis of 3-(4-methoxycarbonyl-2,6-dinitrophenyl)indole, its 2,6-diamino analog, and 3-(2-amino-4-trifluoromethyl-6-nitrophenyl)indole is described. 4-(Trifluoromethyl)phenyl derivatives exhibit higher antibacterial potency than the former 4-(methoxycarbonyl)phenyl homologs, while 3-(4-trifluoromethyl-2-nitrophenyl)indole was the most active agent in the series, with MIC ≈ 7 μg/cm3 against E. coli and S. aureus.
TL;DR: In this paper, the extraction constant corresponding to the equilibrium H+(aq) + 1·Na(nb) ⇆ 1·H+(nb) + Na+(aq)) taking place in the two-phase water-nitrobenzene system (1 = p-tert-butylcalix[4]arene-tetrakis(N, N-diethylacetamide); aq = aqueous phase, nb = nitrobenzinene phase) was evaluated as log Kex(H+, 1· Na+) = −1
Abstract: Summary.From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium H+(aq) + 1·Na+(nb) ⇆ 1·H+(nb) + Na+(aq) taking place in the two-phase water-nitrobenzene system (1 = p-tert-butylcalix[4]arene-tetrakis(N, N-diethylacetamide); aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex(H+, 1·Na+) = −1.4 ± 0.1. Further, the stability constant of the p-tert-butylcalix[4]arene-tetrakis(N,N-diethylacetamide)-H+ complex in water saturated nitrobenzene was calculated for a temperature of 25°C as log βnb(1· H+) = 8.1 ± 0.1.
TL;DR: In this paper, the authors proposed a new protocol for the condensation of aldehydes with quinaldines under microwave irradiation to afford structurally diverse styrylquinolines in high yields under solvent-free conditions.
Abstract: Aromatic aldehydes undergo condensation with quinaldines under microwave irradiation to afford structurally diverse styrylquinolines in high yields under solvent-free conditions. A comparison with the conventional method clearly indicates the advantages of the new protocol.
TL;DR: Farnesyltransferase inhibitors show surprisingly high efficiency in controlling tumor growth in model systems but, so far, clinical trials with human patients have remained without the desired success.
Abstract: Since 1979, when prenylation has been first discovered as chemical oddity of a yeast mating factor, the two forms of this posttranslational modification of proteins (farnesylation and geranylgeranylation) have been found as wide spread among proteins from Eukarya and their viruses. This review attempts to summarize as comprehensively as possible the enzymological processes of prenylation and the various aspects of their biological significance.
TL;DR: In this paper, transparent TiO2 films with a high photodegradation activity towards an azo dye in aqueous solution were prepared by sol-gel processing and shown to exhibit better crystallization and monodisperse nanoparticles, higher absorption of light below 370nm, and higher photocatalytic activity than those films deposited on bare glass supports.
Abstract: Transparent TiO2 films with a high photodegradation activity towards an azo dye in aqueous solution were prepared by sol–gel processing. Films on soda–lime glass supports protected with a thin silica barrier layer exhibited better crystallization and monodisperse nanoparticles, higher absorption of light below 370 nm, and higher photocatalytic activity than those films deposited on bare glass supports proving the detrimental effect of interdiffused sodium ions on the development of the anatase nanostructure. The effect of substrate was more pronounced in thinner films (300 nm) than in thicker ones (1200 nm), which were achieved by adding a template (i.e. Pluronic F127) to the sol.
TL;DR: The conformational preferences of the lignin guaiacyl structural unit were studied at the MP2/6-311G(d,p) level of theory using guaiacol (2-methoxyphenol) as model compound.
Abstract: The conformational preferences of the lignin guaiacyl structural unit were studied at the MP2/6-311G(d,p) level of theory using guaiacol (2-methoxyphenol) as model compound. The potential energy surface of guaiacol was investigated by the ab initio method with full geometry optimization by varying the torsion angles of the guaiacol functional groups (hydroxyl and methoxy). An overall of nine stationary points were located, four of which were found to be minima and the other five transition structures between them. The energy minima of guaiacol can adopt one cisoid and three transoid conformations for the hydroxyl and methoxy groups. The transoid structures differ by the orientation of the methoxy group inside and outside of the aromatic plane. The most stable cisoid conformer has an intramolecular hydrogen bond between phenolic hydrogen and methoxy oxygen with a binding energy of 18.09–18.51 kJ/mol as calculated with the second-order (MP2) and fourth-order (MP4SDQ) Moller-Plesset methods and with larger polarized basis sets including diffuse functions. When comparing the geometrical parameters of the global energy structure with relevant experimental data from crystallographic structures good agreement between the data was found. The saddle points, the effect of calculation level on the energy relative stability, the rotational barrier heights, and the relative concentrations of the conformers are also discussed.
TL;DR: Molecular oxygen is used as an efficient oxidant for the oxidative coupling of thiols to disulfides in subcritical water in the absence of catalysts, providing high yields.
Abstract: Molecular oxygen is used as an efficient oxidant for the oxidative coupling of thiols to disulfides in subcritical water in the absence of catalysts. The procedure utilizes water and does not require support materials and metal salts providing high yields (>90%).
TL;DR: In this paper, the authors used Potassium dodecatungstocobaltate(III) trihydrate as an efficient catalyst for the alcoholyization and acetolysis of epoxides.
Abstract: Efficient ring opening of epoxides under mild conditions is reported. Potassium dodecatungstocobaltate(III) trihydrate was used as an efficient catalyst for the alcoholysis and acetolysis of epoxides. Conversion of epoxides to thiiranes was also performed efficiently in the presence of this catalyst.
TL;DR: In this paper, a catalytic system based on rhodium siloxide can be easily separated from the product and successfully reused up to five times, and it gives heptyl and glycidyloxy functional (poly)siloxanes and silicone polyethers with high yield and selectivity.
Abstract: The hydrosilylation of 1-heptene, allyl glycidyl ether and, allyl polyether by heptamethylhydrotrisiloxane and poly(hydro, methyl)(dimethyl)siloxane catalyzed by rhodium(I) complexes (particularly [{Rh(μ–OSiMe3)(cod)}2]) in imidazolium ionic liquids (especially [TriMIM]MeSO4) gives heptyl and glycidyloxy functional (poly)siloxanes and silicone polyethers with high yield and selectivity. The catalytic system based on rhodium siloxide can be easily separated from the product and successfully reused up to five times.
TL;DR: The one pot reaction preparation, spectral analysis, and molecular modeling experiments on the new 3,4-annelated coumarin systems with bioactivity associated structural features provided the insight into the equilibrium of the respective tautomeric forms making possible the reconciliation of previously published spectral data with the structure assignments as well as the correction of erroneously established structures.
Abstract: The one pot reaction preparation, spectral analysis, and molecular modeling experiments on the new 3,4-annelated coumarin systems with bioactivity associated structural features are described. These provided the insight into the equilibrium of the respective tautomeric forms making possible the reconciliation of previously published spectral data with the structure assignments as well as the correction of erroneously established structures. The synthesized compounds were tested in a standard disk diffusion assay and displayed strong to moderate antimicrobial activity, with a promising new lead prototype compound (7-amino-9-hydroxy-5-oxa-7a,8,11-triazacyclopenta[b]phenanthren-6-one (5)) possessing greater activity that the antibiotics Ampicillin and Nystatin. Antioxidant capacities of the compounds, determined spectrophotometrically using a phosphomolybdenum method, were greater, and in the case of compound 5 four times the activity of α-tocopherol acetate.
TL;DR: In this paper, an ion-bonded AB diblock copolymers and three-arm AB2 asymmetric star-branched polymers comprised of polyacetylene (A) and polystyrene (B) segments have been synthesized by the stoichiometric reaction of tert-amine-chain-end-functionalized poly(phenyl vinyl sulfoxide)s with either chain-end or inchain-carboxylated polystyrenes to link the two polymer segments via ionic bond, followed by thermal treatment to convert their poly (phenyl
Abstract: Novel ion-bonded AB diblock copolymers and three-arm AB2 asymmetric star-branched polymers comprised of polyacetylene (A) and polystyrene (B) segments have been synthesized by the stoichiometric reaction of tert-amine-chain-end-functionalized poly(phenyl vinyl sulfoxide)s with either chain-end- or in-chain-carboxylated polystyrenes to link the two polymer segments via ionic bond, followed by thermal treatment to convert their poly(phenyl vinyl sulfoxide)s to polyacetylene segments. Periodic lamellar morphologies were observed in the cast films of such polymers by TEM measurement. The isolation of the nano-size sheet consisting of polyacetylene lamellar layers was attempted.
TL;DR: The surface modification of nanoparticles via azide/alkine-1,3-dipolar cycloaddition-reactions is described and ligand exchange onto various nanoparticles was monitored by 1H NMR spectroscopy and formed the basis for the attachment of ligands onto the nanoparticles and their subsequent modification by dipolar cycloadDition reactions.
Abstract: The surface modification of nanoparticles via azide/alkine-1,3-dipolar cycloaddition-reactions is described. Ligand exchange onto various nanoparticles was monitored by 1H NMR spectroscopy and formed the basis for the attachment of ligands onto the nanoparticles and their subsequent modification by dipolar cycloaddition reactions. Nanoparticle-surfaces were monitored by binding onto self-assembled monolayers derivatized with matching supramolecular interactions after derivatization.
TL;DR: Complexes of Pt(II, Pd(II), and Ni(II) with the condensation derivative of 2-(diphenylphosphino)benzaldehyde and semioxamazide were synthesized, characterized, and their antimicrobial activity was evaluated as mentioned in this paper.
Abstract: Complexes of Pt(II), Pd(II), and Ni(II) with the condensation derivative of 2-(diphenylphosphino)benzaldehyde and semioxamazide were synthesized, characterized, and their antimicrobial activity was evaluated. The ligand and the complexes were characterized by spectroscopic methods with the particular accent on NMR spectral analysis. For the palladium(II) complex, the crystal structure was determined by X-ray analysis. In all the complexes the ligand is coordinated as a tridentate via a P, N, O donor set. The Pd(II) and Pt(II) complexes have a square planar geometry, whereas the geometry of the Ni(II) complex is tetrahedral. The ligand showed antibacterial and antifungal activity, which was enhanced upon complexation.
TL;DR: In this article, a Pitzer model representing the thermodynamics of alkaline sodium aluminate solutions is presented, which constitutes a key part of our 10-component synthetic Bayer liquor model communicated in this series of papers.
Abstract: A Pitzer model representing the thermodynamics of alkaline sodium aluminate solutions is presented. It constitutes a key part of our 10-component synthetic Bayer liquor model communicated in this series of papers. The present model calculates thermodynamic properties, such as heat capacities, osmotic coefficients, and densities, of these solutions as well as the solubilities of gibbsite and boehmite over temperature and concentration ranges of industrial interest.
TL;DR: A novel process for the one-step chemoselective conversion of alkyl halides into carbamates as protected amines was developed using benzyltrimethylammonium hydroxide (Triton-B) in presence of gaseous carbon dioxide.
Abstract: A novel process for the one-step chemoselective conversion of alkyl halides into carbamates as protected amines was developed using benzyltrimethylammonium hydroxide (Triton-B) in presence of gaseous carbon dioxide. Thus, carbamate esters of different amines were prepared in very good to excellent yields.
TL;DR: In this paper, it was shown that both the total π-electron energy (E), the topological resonance energy (DRE), and the Dewar resonance energy are well correlated with Kekule-and Clar-structure-based parameters.
Abstract: Within classes of isomeric benzenoid hydrocarbons various Kekule- and Clar-structure-based parameters (Kekule structure count, Clar cover count, Herndon number, Zhang–Zhang polynomial) are all mutually correlated. This explains why both the total π-electron energy (E), the Dewar resonance energy (DRE), and the topological resonance energy (TRE) are well correlated with all these parameters. Nevertheless, there exists an optimal value of the variable of the Zhang–Zhang polynomial for which it yields the best results. This optimal value is negative-valued for E, around zero for TRE, and positive-valued for DRE. A somewhat surprising result is that TRE and DRE considerably differ in their dependence on Kekule- and Clar-structure-based parameters.
TL;DR: A novel process for the one-step chemoselective conversion of a variety of alcoholic tosylates into carbamates serving as protected amines was developed using benzyltrimethylammonium hydroxide (Triton-B) in the presence of gaseous carbon dioxide.
Abstract: A novel process for the one-step chemoselective conversion of a variety of alcoholic tosylates into carbamates serving as protected amines was developed using benzyltrimethylammonium hydroxide (Triton-B) in the presence of gaseous carbon dioxide. Thus carbamate esters of different amines were prepared in very good to excellent yields.
TL;DR: A novel process for the one-step chemoselective conversion of alkyl halides into dithiocarbamates as protected amines was developed using benzyltrimethylammonium hydroxide (Triton-B) in presence of carbon disulfide.
Abstract: A novel process for the one-step chemoselective conversion of alkyl halides into dithiocarbamates as protected amines was developed using benzyltrimethylammonium hydroxide (Triton-B) in presence of carbon disulfide. Thus, dithiocarbamates of different amines were prepared in very good to excellent yields. This protocol is mild, chemoselective, and efficient compared to other methods.
TL;DR: In this paper, it was observed that a difference of more than 0.033 A between the longest and shortest W-S bonds in a tetrathiotungstate will result in the splitting of the asymmetric stretching vibration of the W-s bond.
Abstract: Four new organic ammonium tetrathiotungstates (N–Me–enH2)[WS4] (1), (N,N′-dm-1,3-pnH2)[WS4] (2), (1,4-bnH2)[WS4] (3), and (mipaH)2[WS4] (4), (N–Me–enH2 = N-methylethylenediammonium, N,N′-dm-1,3-pnH2 = N,N′-dimethyl-1,3-propanediammonium, 1,4-bnH2 = 1,4-butanediammonium, and mipaH = monoisopropylammonium) were synthesized by the base promoted cation exchange reaction and characterized by elemental analysis, infrared, Raman, UV-Vis and 1H NMR spectroscopy as well as single crystal X-ray crystallography. The structures of 1–4 consist of [WS4]2− tetrahedra which are linked to the organic ammonium cations via N–H⋯S hydrogen bonding. The strength and number of the S⋯H interactions affect the W–S bond lengths as evidenced by distinct short and long W–S bonds. The IR spectra exhibit splitting of the W–S vibrations, which can be attributed to the distortion of the [WS4]2− tetrahedron. From a comparative study of several known tetrathiotungstates it is observed that a difference of more than 0.033 A between the longest and shortest W–S bonds in a tetrathiotungstate will result in the splitting of the asymmetric stretching vibration of the W–S bond.