Manfred Lissel

Oxidation of activated phenols by dioxygen catalysed by the H5PV2Mo10O40 heteropolyanion

Abstract The H 5 PV 2 Mo 10 O 40 heteropolyanion has been found to catalyse the highly selective aerobic oxidation of dialkylphenols to diphenoquinones and the oxidation of 2, 3, 5-trimethylphenol to the 2, 3, 5-trimethyl-1, 4-benzoquinone. The rate is highly dependent on the oxidation potential of the substrate and is proceeds by electron transfer from the phenol substrate to the heteropolyanion catalyst.

A convenient route to alkynes via phase transfer catalysis: Applications of phase transfer catalysis, part 19

High yield, rapid formations of alkynes from vicdibromides are possible using powered potassium hydroxide and catalytic amounts of lipophilic phase transfer catalysts. Reasons are given why molar amounts of expensive catalysts were necessary in earlier procedures.

Anwendungen der phasentransfer-katalyse—4: Halogenaustausch und reaktivitäten bei dibrom-, chlorbrom- und dichlorcarben

Abstract Exchange with external halogenide is possible in phase transfer catalytical generations of dihalocarbenes. CHBrCl2 and CHBr2Cl yield adducts of all three possible combinations, CBr2, CBrCl and CCl2. Consumption of haloform is accelerated by the presence of olefin, the amount of hydrolysis competing with carbene formation, however, is reduced thereby. Contrary to claims in the literature no optical induction is observed in CX2 additions. These results support once more the intermediacy of free CX2. CBr2 is more reactive and electrophilic than CCl2 under phase transfer catalysis conditions, again contrary to literature claims. An example of a differing mode of reaction of chloroform and bromoform is given.

Bis-quaternary ammonium salts as phase transfer catalysts

Bis-quaternary ammonium salts are used for the extraction of polyanions and show better extractive abilities than common phase transfer catalysts.

Metabolite fingerprinting of barley whole seeds, endosperms, and embryos during industrial malting

Samples of whole seeds, isolated endosperms including the aleurone layer and isolated embryos with attached scutellum from an industrial scale barley malting process (variety Braemar) were analysed for their water soluble metabolites by gas chromatography-mass spectrometry (GC-MS). 73 known metabolites and about 350 unknown signals were detected. Principal component analysis (PCA) showed a time dependent shift of sample profiles. Whole seeds and endosperm samples showed very similar patterns with nearly all compounds rising until the end of germination. In the embryos a maximum concentration of compounds was reached after 72-96 h of malting. Most concentrations decreased afterwards. The kilning step, namely the drying and roasting of germinated seeds, induced variable effects of increases, stability or decreases of metabolites and thereby separated kilned samples from germinated seeds in the PCA. A second barley cultivar (Quench) underwent the same malting and analysis procedures and gave nearly identical results. Fructose, malate, myo-inositol and raffinose exhibited the potential to serve as markers for specific developmental stages of seeds in both varieties. Biological markers represent targets for industrial process control. Their potential application would meet the maltsters demand to flatten variances in germination properties and to produce equal composed malt by directed malting management.

Phase Transfer Catalysis for the Preparation of Trimethylsilyl and Tert-Butyldimethylsilyl Ethers

Abstract The trimethylsilyl group is widely used for the protection and analysis of hydroxyl functions1). A large number of methods have been described and many reagents have been developed1, 2). We wish to introduce here a new procedure based on Phase Transfer Catalysis (PTC)3). The silylation of alcohols with chlorotrimethylsilane is performed in the presence of dry potassium carbonate or sodium carbonate as base and Aliquat 3364) as PT-Catalyst.

Unusual Outer Membrane Lipid Composition of the Gram-negative, Lipopolysaccharide-lacking Myxobacterium Sorangium cellulosum So ce56

The Gram-negative myxobacterium Sorangium cellulosum So ce56 bears the largest bacterial genome published so far, coding for nearly 10,000 genes. Careful analysis of this genome data revealed that part of the genes coding for the very well conserved biosynthesis of lipopolysaccharides (LPS) are missing in this microbe. Biochemical analysis gave no evidence for the presence of LPS in the membranes of So ce56. By analyzing the lipid composition of its outer membrane sphingolipids were identified as the major lipid class, together with ornithine-containing lipids (OL) and ether lipids. A detailed analysis of these lipids resulted in the identification of more than 50 structural variants within these three classes, which possessed several interesting properties regarding to LPS replacement, mediators in myxobacterial differentiation, as well as potential bioactive properties. The sphingolipids with the basic structure C9-methyl-C20-sphingosine possessed as an unusual trait C9-methylation, which is common to fungi but highly uncommon to bacteria. Such sphingolipids have not been found in bacteria before, and they may have a function in myxobacterial development. The OL, also identified in myxobacteria for the first time, contained acyloxyacyl groups, which are also characteristic for LPS and might replace those in certain functions. Finally, the ether lipids may serve as biomarkers in myxobacterial development.

Über die reaktion von α- und β -tetralon mit kaliumsuperoxid

Abstract The reaction of α- and β-tetralone with potassium superoxide is described. In addition to 2-hydroxy-1,4-naphthoquinone α-naphthol is formed from α-tetralone and β-naphthol and 2-carboxy-benzenepropionic acid from β-tetralone.

Oxidative Spaltung von Ketonen mit Kaliumsuperoxid: (Anwendunqen der Phasentransfer-Katalyse 8)

Kaliumsuperoxid liifit sich durch Komplexierung mit Kronenethern in aprotische Losungsmittel iiberfiihren und wird so als Partner fiir organische Reaktionen interessent*. K02 kann dabei als Oxidationsmittel, als Reduktionsmittel und als Nucleophil reagieren. Bisher wurden stets die teuren Kronenether als Phasentransfer-Katalysatoren verwendet. Nachdem bereits Reaktionen des Superoxids mit Enonen wie Tetracyclon und mit Chalkonen bekannt sind2, berichten wir jetzt, d&i (a) entgegen friiheren Angaben such nicht-aktivierte Ketone umgesetzt werden und (b) d& diese Reaktionen such mit billigen quartaren Ammoniumsalzendurchgefiihrt werden k6nnen. Die Oxidation der Ketone mit einem UberschuR Kaliumsuperoxid in 3enzol liefert in kurzer Reaktionszeit ( 1 8 Std. ) bei Raumtemperatur in guter Ausbeute Carbonsauren. Werden cyclische Ketone in die Reaktion eingesetzt, so isoliert man die a,oDicarbonsauren. Die Phasentransfer-Katalysatoren miissen im verwendeten Medium ( Benz01 oder Petrolether ) gut lijslich sein. Beispielsweise ist TEBA ungeeignet; wir bevorzugen Aliquat 3363. Die erhaltenen Ergebnisse sind in Tabelle 1 zusammengefaRt. Kronenether als Phasentransfer-Katalysatoren bringen keinen Vorteil gegeniiber Aliquat 336. Ausbeute und Reaktionszeit sind in beiden Fallen vergleichbar. Eine mechanistische Diskussion ( vgl. 4, erscheint uns verfriiht. An dieser Stelle mb;chten wir jedoch auf folgende Seobachtungen hinweisen : (1) Es tritt keine Sauerstoffentwicklung auf. (2) Ketone ohne a-Wasserstoff (u.a. such 3enzophenon)sind unter diesen Bedingungen inert. (3) Auch 1,3-Diketone reagieren nicht.

Dechlorination of perchlorinated aromatic compounds by graphite-potassium-intercalate

Abstract Potassium-graphite-intercalate (C 8 K) completely dechlorinates perchlorinated aromatic compounds in a few minutes. Beside preparative utilizations we found the reaction applicable for the degradation and detoxification of chlorinated compounds.