Selektive Umsetzungen von Kohlenhydraten mit Isocyanaten

Selective Reactions of Carbohydrates with Isocyanates 6-O-Arylcarbamoyl-D-galactose dialkyl dithloacetals 2a–n are prepared by selective reactions of D-galactose dialkyl dithioacetals with aryl isocyanates in pyridine. Some of them are acetylated to give the 2,3,4,5-tetra-O-acetyl derivatives 3a, b, i–m . The structures of the compounds 2 and 3 are proved by further synthesis from 1,2;3,4-di-O-isopropylidene-D-galactose or 2,3,4,5-tetra-O-acetyl-D-galactose diethyl dithioacetal, respectively.     

Über die Spaltung von PVC mit Alkali in Tetrahydrofuran

With the objective of scanning the molecular structure of PVC, its reaction with alkali in tetrahydrofurane which has been published previously was reexamined in detail. It was found that, stirring of a 1% solution of PVC in THF with KOH/MeOH at room temperature or 60°C for 90 min yields a product which has only two-thirds of the original K-value. If reacted at room temperature 16 molecules of HCl per 100 VC-units will be eliminated, obtaining at the same time 12 double bonds and the introduction of 2 oxygen atoms. If the splitting is performed at 60°C, 30 molecules of HCl per 100 VC-units will be eliminated obtaining 15 double bonds and the introduction of 10 oxygen atoms. Analysis by gelpermeation chromatography in combination with balance of materials indicates that parallel to chain splitting an increase in molecular weight takes place possibly by intermolecular elimination of HCl. As compared to reactions with low molecular weight compounds the possibility will be discussed that the splitting of the chain in THF could have proceeded at a head-to-head-addition site after HCl elimination followed by saponification (retroaldolreaction).     

Die reaktion von diandiglycidyläther mit aromatischen diaminen

m-Phenylendiamine, p,p'-diaminodiphenylmethane and p,p'-diaminodiphenylsulphone were evaluated as hardeners for low molecular weight epoxide resins, and basic physical constants characterizing the kinetics of the reaction of diglycidylether of diane with the above hardeners were determined. Using the relation between viscosity, average molecular weight, and degree of reaction it was possible to characterize the existence range of the so-called epoxide-pregels which are formed from mixtures of epoxide resins with aromatic amines at lower temperatures. The applicability of SMITHS equation related to the kinetics of reaction between epoxidic compounds and amines was verified. The kinetic of reaction indicates the existence of hydrogen bonds at the epoxide groups, it may be assumed, however, that the presence of these relatively strong intermolecular bonds affects even the rate of pregelation.     

Studium der Reaktivität von aromatischen Diaminen mit Epoxidharzen

It was found that the deciding factor for the reactivity of aromatic diamines with epoxide resins are basic values of electron structure and chemical reactivity on the end amino-groups. A linear dependence was determined between logarithm of gelatinization time and electron density of the amino-group which was calculated using principles of quantum chemistry. Changes in the structure of aromatic diamines leading to changes of the electron density of amino-group cause a reactivity change of these compounds during polyaddition. This method shows possibilities offered by quantum chemistry in the field of plastics.     

Spaltung von 1,2,4-Thiadiazol-3-onen mit Triphenylphosphan: Triphenylphosphonio-thioimidazolate und ihre Folgereaktionen

Fission of 1,2,4-Thiadiazol-3-ones by Triphenylphosphane: gewidinet Triphenylphosphonio Thioimidazolates and Their Consecutive Reactions Treatment of benzimidazo[1,2-d][1,2,4]thiadiazol-3(2H)-ones ( 1 ) and imidazo[1,2-d]-[1,2,4]thiadiazol-3(2H)-ones ( 17 ) with triphenylphosphan leads to the liberation of isocyanate and the formation of triphenylphosphonio-thiobenzimidazolat ( 4 ) and triphenylphosphonio-thioimidazolat ( 18 ), respectively. 2,4-Diphenyl-5-phenylimino-1,2,4-thiadiazol-3-one ( 23 ) is desulfurized with Ph₃P and decomposed into phenyl isocyanate and diphenylcarbodiimide whereas the N-unsubstituted imino-thiadiazol-3-one ( 25 ) is attacked at the exocyclic imino group by Ph₃P to give the N-phosphoranylidene thiourea ( 26 ). The structure of 4 can be rationalized as a dynamic system between polar and apolar valence isomeres. Reactions of 1 and 17 with cyanates, isocyanates, carbon disulfide, acetic anhydride, amines, benzyl chloride, grignard compounds, and CH acidic compounds are described.     

Zirkonium-katalysierte Oxidation von primären aromatischen Aminen zu Nitroverbindungen mit tert-Butylhydroperoxid

Zirconium-catalysed Oxidation of Primary Aromatic Amines to Nitro Compounds Using tert-Butylhydroperoxide A broad range of primary aromatic amines ( 1a–x ) with electron donating and accepting substituents are oxidized in good to excellent yields to the nitro compounds 3a–x using tert-butylhydroperoxide as the oxidant and Zr(OtBu)₄ as the catalyst. The corresponding nitroso compounds 2m, 2n, 2s and 2u can be isolated in the conversion of electron-rich anilines 1m, 1n, 1s and 1u . The aminopyridines 5a–d are also converted to the corresponding nitropyridines 6a–d , but in lower yields (41–47%).     

Selektive Abtrennung von Indium und Germanium aus Laugungslösungen mit Membranverfahren

The increasing demand for the strategic elements indium and germanium necessitates the development of new extraction methods. The goal of the presented study is the development of a sustainable method for the selective recovery of indium and germanium from leaching solutions within a bioleaching process. Rather than commonly used solvent extraction the application of membrane technology, in particular nanofiltration and supported liquid membrane, has been investigated. Results with nanofiltration show that indium and germanium can be separated selectively depending on the pH value of the solution. Furthermore, extraction of indium from a concentrated solution containing Zn, Cu, Fe, and As using supported liquid membrane was performed successfully.     

Komplexe des Eisens mit aromatischen Liganden

Complexes of Iron with Aromatic Ligands The reaction of FeCl₃ · 6 H₂O with several substituted o-phenylene diamines forms complexes of the Fe(II)-ion with o-quinone diimines. Before the formation of these complexes there are a few of redox reactions between Fe(III)ions and the diamines. The Fe(III)/o-quinone diimine-complex is an intermediate which was characterized by means of spectroscopic methods. The two forms of 6-oxy-7-nitrosobenzthiazoline produce only one 1:3 complex with Fe(II)ions. Also the N-methyl-6-oxy-7-nitrosobenzthiazolium iodide forms a 1:3 complex. In the former complex the quinone-oxim-form is the ligand. The isolated complexes were characterized through elemental analysis and physical methods.     

Selektivhydrierung von Fettstoffen mit metallorganischen Mischkatalysatoren nach Ziegler-Sloan-Lapporte I: Selektive Hydrierung von Linolsäuremethylester und Modelldienen mit isolierten Doppelbindungen

Selective Hydrogenation of Fats and Derivatives Using Ziegler-Type Organometallic Catalysts I: Selective Hydrogenation of Methyllinoleat and Other Dienic Compounds with Isolated Double Bonds Homogeneous catalysts of Ziegler-Sloan-Lapporte-type, containing nickel, cobalt or palladium, were used to hydrogenate methyllinoleate under very mild conditions selectively to monounsaturated products. The question, wether this selectivity is caused by the 1,4-position of the olefinic double bonds, led to hydrogenation experiments with non-conjugated α,ω-dienes of different chain length. A significant selectivity was only observed for the reduction of 1,4-pentadiene to pentene, dienes with greater distance between the double bonds than in linoleic acid were hydrogenated with less selectivity. To explain these facts, a kinetic model, including catalyst-substrate-complexes of different stabilities, is proposed.     

Cyclofunktionalisierung von 2-Allyl-phenolen mit Schwefelchloriden 2,3-Dihydrobenzofurfurylthioether aus 2-Allyl-phenolen und aromatischen Sulfenylchloriden

Cyclofunctionalization of 2-Allyl-phenols with Sulfur Chlorides. Synthesis of 2,3-Dihydrobenzofurfuryl Thioethers by the Reaction of 2-Allyl-phenols with Aromatic Sulfenyl Chlorides Reactions of different substituted 2-allyl-phenols ( 2a – h ) with either phenylsulfeny chloride ( 3 ) or 4-methyl phenylsulfenyl chloride ( 4 ) yield the products of a cyclofunctionali zation 2-phenylthiomethyl 2,3-dihydrobenzofuranes ( 6a – h ) or 2-(4′-methylphenyl) 2,3-dihydrobenzofurane ( 7a – g ), respectively. The identification of the products was carried out by mass spectroscopy and ¹H-n.m.r.-spectroscopy. Isomeric compounds, i.e. 3-phenylthio 2,3-dihydrobenzopyranes ( 10 ) were not obtained. The reaction is Markovnilov-directed. In the case of the treatment of 2-allyl-phenols with 2-nitro phenylsulfenyl chloride ( 5 ) we have obtained mixtures of 2-(2′-nitrophenyl) thiomethyl 2,3-dihydrobenzofuranes ( 8a – d ) and of simple Markovnikov adducts, so-called β-chlorothioethers. The mixtures were identified by ¹H-n.m.r.- and mass spectroscopic ( 9a – d ) methods.     

Identifizierung von Zwischenprodukten der Lichtinduzierten Spaltung von σ-Alkyl-Co(III)-Komplexen mit Hilfe von spin-trapping-Experimenten

Identification of Intermediates in the Photolysis of Some σ-Alkyl Cobalt Complexes using the Technique of Spin Trapping In the aerobic photolysis of the complexes [R¹Co(chel)Y] (R¹ = CH₃, C₂H₅, n-C₃H₇; chel = salen, salphen; Y = H₂O, C₅H₅N, P(C₆H₅)₃) and [RCo(bipy)₂]X (R² = CH₃, n-C₃H₇, C₆H₅CH₂; X = ClO₄, J) in chloroform alkyl-, alkoxy and hydroxyalkyl radicals are detected using the technique of spin trapping. Moreover, in the presence of phenyl tert.-butyl nitrone the photolysis of the ethyl and propyl complexes [RCo(chel)Y] produces the spin adduct of H at phenyl tert.-butylnitrone. From these results we conclude that photochemically the hydridocomplexes [HCo(chel)Y] are formed.