Komplexkatalyse mit Technetiumverbindungen: Hydroformylierung mit Technetiumcarbonyl-Katalysatoren

Complex Catalysis with Technetium Compounds. Hydroformylation with Technetiumcarbonyl Catalysts The hydroformylation reaction of cyclohexene ( 1 ), propene ( 2 ) and 1-octene ( 3 ) was studied using Tc₂(CO)₁₀ and Tc(CO)₁₀/P(n-C₄H₉)₃, resp., as catalysts in solution. For comparison experiments have also been made with Mn₂(CO)₁₀, Mn₂(CO)₁₀/P(n-C₄H₉)₃ and Re₂(CO)₁₀/P(n-C₄H₉)₃ as catalysts for the hydroformylation of 1 . There is always a competition between hydrogenation and hydroformylation. Tc₂(CO)₁₀/P(n-C₄H₉)₃ gave the best results in activity and selectivity within the subgroup VII complexes studied, but is a rather poor catalyst compared with the cobalt or rhodium compounds.     

Funktionallsierung von lodprazolen mit D-Glucopyranose bzw. mit Aminoalkoholen

Functionalisation of Iodopyrazoles with D-Glucopyranose and with Aminoalcohols, Respectively . 3, 4, 5-Triiodo-pyrazole ( 1a ) and 3, 4-diiodo-5-methyl-1 H-pyrazole ( 1 b ) were silylated with hexamethyldisilazane without isolation of the N-trimethylsily derivatives and than glucosilated to give the β-N-nucleosides 2a and 2b , respectively, with 2, 3, 4, 6-tetra-O-acetyl-α-D-glucopy-ranosylbromide or -fluoride in the presence or absence of SnCl₄. The corresponding deacetylated derivatives 3 a – b can be easily obtained by treatment of 2 a – b with sodium methanolate in methanol. Furthermore, 1 a and 1 b as well as 3(5)-methoxycarbonyl-4-iodo-1-H-pyrazole ( 1 c ) were alkylated with methyl bromoacetate-acetate to form the corresponding pyrazole-1-yl-methylacetates 4 a – c . These compounds could be amidated by short heating with N-methylglucamine and 1-amino-propane-2, 3-diol (isoserinol), respectively, in methanol to form the corresponding amides 5 a – c and 6 a – c . The diamide 7 c was prepared bylongtime heating of 4 c with excess isoserinol in n-propanol.     

Erfahrungen mit Mehrproduktanlagen

Experience Gained with Multipurpose Plants. Multipurpose plants are used in many fields of production. Some products often have a short life cycle or are not in continuous demand; hence these plants undergo constant changes. In order to control these changes from an economical point of view, certain boundary conditions must be met. The following article describes which questions have to be asked and answered and which structures prove to be advantageous for such plants.     

Butadien-Polymerisation mit Alfin-Katalysatoren

The course of the butadiene polymerization with Alfin-catalysts is investigated. During the beginning of the polymerization high molecular weight polymers are formed. The addition of n-donors yields lower molecular weight polymers with, at times, altered structures. Triphenylphosphine reduces the molecular weight without affecting the structure. The addition of nickel compounds to Alfin-catalysts does not bring about an increase of the cis-content of the polymers. The rate of the butadiene-polymerisation with unmodified Alfin-catalysts is therefore considerably higher than that with nickel containing Ziegler catalysts.     

Estersynthesen mit Lipasen

Synthesis of Esters by Lipases Lipases belong to the enzymatic class of hydrolases and catalyse both the hydrolysis and synthesis of esters at the interface between water and insoluble substrate. Esterification by lipases is possible at ambient temperature and at neutral pH under normal pressure in simple reaction vessels. Lipases have potential uses in the preparation of wax esters, fragrances, ester oligomers and other compounds. Ester synthesis by lipases may be performed either batch-wise or continuously. Examples for stereoselective esterification have been reported e.g. in the selective preparation of l-menthylester from dlmenthol. Regio-specific lipases, catalysing transesterification of position 1 and 3 of the triglyceride, are applied to the production of valuable products such as cocoa butter substitutes. Transesterification of triglycerides and methanol results in fatty acid methyl esters.     

Gas-Trennung mit Membranen

Gas Separation with membranes . Gas separation with membranes has already been tested in numerous fields of application, e. g. uranium enrichment or H₂ separation. In many of these processes the mass transfer units, so-called permeators, have to be connected in tandem in order to achieve high concentrations. A most economical operating method provides for each case an optimization of the cascades with regard to the membrane materials, construction and design of module. By utilization of the concentration gradient along the membrane a new process development has been accomplished – the continuously operating membrane rectification unit. Investment and operating costs can be reduced considerably for a number of separating processes by combining a membrane rectification unit with a conventional recycling cascade. However, the new procedure requires that the specifications for the module construction, flow design, and membrane properties be reconsidered.     

Kreislaufreaktor mit Konzentrationsregelung

The Concentration-Controlled Recycle Reactor. The scope offered by the concentration-controlled recycle reactor for elucidatin the kinetics of heterogeneous gas reactions is presented in three contexts: identification of reaction networks; experimental design; and separate determination of changes of activity. Control strategies appropriate for the problem at hand are an essential prerequisite for the application of experimental strategies. In particular, long analysis cycles require appropriate modification of modern methods of control theory. Various model-based control concepts have been developed and tested by experiment and simulation.     

Gastrennung mit Druckwechsel-Adsorptionsanlagen

Gas separation in pressure swing adsorption plant . In recent years gas separation in pressure swing adsorption plant has acquired considerable significance as an industrially implemented process. This is particularly true of plant for isolation of pure hydrogen from gas mixtures of various origins. Starting from the underlying principles, this contribution considers the various types of plant for hydrogen isolation, for obtaining carbon monoxide, for recovery of ethylene, for separation of oxygen or nitrogen from the air, and for ozone isolation.     

Heterocyclenbildung mit Enaminen

Heterocycles from Enamines Aminoacrylderivatives ( 1 ) and Br₂/NH₄SCN form iminothiazolinones 3a–c and with chlorosulfonylisocyanate thiadiazinonedioxide 8 . Reaction of 3 a with hydrazine yields disulfide 6 . Compound 2 and PCl₃ yield diazaphosphorines 7a–c . By reaction of pyrimidinone 9 with NaOCl, HCl/H₂O₂ or Br₂/NH₄SCN dichloropyrimidinone 10 , dichlorooxaziridine 16 , and thiocyanate 13 are formed. Octahydroquinazolinone ( 17 ) and NaOCl or H₂O₂/HCl form chloroderivatives 18, 19 and 20, 18 with peracid oxaziridine 22 . Compounds 16, 21, 22 and 13 with NaOCl form N-chloroderivatives 23, 24, 25 and 26 resp.     

Reaktionen mit Thio-bis-formamidinen

Reactions with Thio-bis-formamidines N,N,N′-Trisubstituted S-(4-amino-s-triazin-2-yl)-isothioureas 3 are prepared in good yields form trisubstituted thio-bis-formamidine-hydrochlorides 1 and esters of cyanimidocarboxylic acids 2 . In aqueous alkali solutions compounds 1 react with β-dicarbonyl compounds under rearrangement to yield substituted N-(pyrimidin-2-yl)-thioureas 4 and 5 .     

Hexaazapolycyclen durch selektive Multimethylenierungen mit Dichlormethan und Base oder mit Urotropin

Hexaazapolycycles by Selective Multimethylenations with Dichloromethane and Base or with Hexamethylenetetramine Multiple methylenations of 2-aminomethylbenzimidazole with dichloromethane and methylamine or ammonia or with hexamethylenetetramine lead to highly selective formations of 6 new single bonds to give only a polycyclic bis-spiro-1,5-diazocine 2 or only a polycyclic spiro-1,3,6-triazonine 4 or only a polycyclic 1,3,6,8-tetrazecine derivative 6 . 4 and 6 may be equally well obtained starting with 2-chloromethyl-benzimidazole. All of these selectively formed products are concave cryptands with 6 amino nitrogen atoms. No template metals are used in their syntheses. The reasons for the unusual changes in selectivity are investigated using semi-empirical PM3 calculations and mechanistic considerations. Experimental and spectroscopic details are given.     

Ethanol-Herstellung mit Bakterien

Ethanol production with bacteria . Strains of Saccharomyces cerevisiae have mostly been used for the production of ethanol from sugar by yeasts. Recently it was shown that the bacterium Zymomonas mobilis has some advantages compared to yeast for the production of industrial alcohol. Compared to traditional yeast fermentation, ethanol yield is about 5% higher than with yeast, since less sugar is incorporated into cell material by this bacterium. Like yeast, Zymomonas mobilis has remarkably high ethanol tolerance which enables the bacterium to produce ethanol concentrations of more than 13 vol.-% from sugar solutions of appropriate concentration. Investigations of the spectrum of lipids present have shown that this bacterium contains large quantities of hopanoids which are presumably of significance for the stabilization of cell membranes in the presence of ethanol. Since the cost of the sugar greatly influences the profitability fraction formed in the production of glucose syrup from wheat flour was investigated. It was shown that after enzymatic saccharification of this waste starch the glucose was efficiently fermented to ethanol by Zymomonas mobilis. It is planned to broaden the substrate spectrum of Zymomonas mobilis by gene cloning techniques so that in future pentoses, e. g. xylose or arabinose, can also be fermented to ethanol by this organism.