Manfred Michalik
University of Rostock
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Featured researches published by Manfred Michalik.
Aquatic Sciences | 2002
Uwe Selig; Thomas Hübener; Manfred Michalik
Abstract. Soluble and particulate phosphorus forms in the surface water of the eutrophic shallow Lake Bützow were investigated from March to November 1998. Soluble reactive phosphorus (SRP) and dissolved organic phosphorus (DOP) of the filtered water were analysed. Suspended particulate matter (SPM) was characterized by particulate organic matter (POM), particulate organic carbon (POC), particulate phosphorus (PP), particulate iron (PFe), phytoplankton biomass (PB) and Chl a. PP was investigated in more detail by means of sequential chemical extraction (Psenner et al., 1984) and the analysis of polyphosphates and phospholipids.¶ In spring, the lowest SRP values and highest PP values were recorded. Over the course of the year, SRP did not decline, whereas DOP increased and became the dominant P-pool in the lake in autumn. Polyphosphate, as a reserve compound in algae, was present only until July. Its decline was accompanied by an increase in phospholipids and a decrease in the easily available PP and the sorptive-bound PP. The levels of iron-bound phosphorus and the apatite-phosphorus remained stable over the year. The available phosphorus declined, although the SRP level never dropped below 0.015 mg L-1. Thus, insufficient phosphorus was available in this eutrophic lake to allow formation of polyphosphate granules in algae in the second half of the year. Neither SRP nor the elemental composition of seston is suitable to describe the P-status and deficiency for algal growth in the shallow Lake Bützow.
Journal of Fluorine Chemistry | 1997
Oliver Klenz; Rainer Evers; Ralf Miethchen; Manfred Michalik
Abstract Monoalkylations of different nucleophilic azoles were investigated with the electron-deficient trans-3,3,3-trifluoro-1-nitropropene (1) as alkylating reagent without addition of any catalyst. In each case, the bonding of the alkene at the azole occurs regioselectively at the trifluoromethyl-substituted C atom of the alkene, whereas the azoles react at different positions depending on the electron density of the heterocycles. Thus, 1-methyl-pyrrole (2) reacted with 1 under C-C bond formation giving the two regioisomers 2-(1-trifluoromethyl-2-nitroethyl)-1-methyl-pyrrole (3) (major product) and 3-(1-trifluoromethyl-2-nitroethyl)-1-methyl-pyrrole (4). The less nucleophilic pyrazole (5), 1,2,4-triazole (7), 3-bromo-1,2,4-triazole (9), and 3,5-dibromo-1,2,4-triazole (12) gave exclusively the corresponding N-alkyl azoles 1- (1-trifluoromethyl-2-nitroethyl )-pyrazole (6), 1-(1-trifluoromethyl-2-nitroethyl) -1,2,4-triazole (8), 3-bromo-1- (1-trifluoromethyl-2-nitroethyl)-1,2,4-triazole (10)/5-bromo-1-(1-trifluoromethyl-2-nitroethyl)-1,2,4-triazole (11), and 3,5-dibromo-1-(1-trifluoromethyl-2-nitroethyl)-1,2,4-triazole (13), respectively. The enantiomeric pairs of the chiral monoalkyl-azoles could not be separated. Moreover, we used trans-3,3,3-trifluoro-1-nitropropene (1) as a dienophile in Diels-Alder cycloadditions with cyclopentadiene (14), cyclohexa-1,3-diene (16), and furan (18). Two diastereomeric products (15A/15B, 17A/17B, and 19A/19B), which could not be separated by column chromatography, are formed from each diene. All compounds were characterized by 1H, 13C, and 19F NMR data.
Carbohydrate Research | 2000
Manfred Michalik; Martin Hein; Michael Frank
Recent advances in structural and conformational analysis of fluorinated carbohydrates by NMR spectroscopy are reviewed. Characteristic 1H, 13C, and 19F NMR chemical shifts and coupling constants for selected examples are given and the spectral data of a series of fluorinated carbohydrates were collected in continuation of the review of Csuk and Glänzer [Adv. Carbohydr. Chem. Biochem., 46 (1988) 73-177].
Tetrahedron Letters | 1999
Annegret Tillack; Dirk Michalik; Cornelia Koy; Manfred Michalik
Abstract The Rh-catalyzed hydrosilylation of butadiynes to chiral allenes in the presence of chiral phosphine ligands is described. For the first time an enantiomeric excess of 22% was achieved using PPM ligand ((2S,4S)-(−)-4-(diphenylphosphino)-2-(diphenylphosphinomethyl)-pyrrolidine).
Journal Fur Praktische Chemie-chemiker-zeitung | 2000
Björn Kuhla; Klaus Peseke; Gabriela Thiele; Manfred Michalik
The push-pull functionalization of the ulose 1 to give the (E)-configurated dimethylaminomethylene pyranosidulose 2 was achieved with bis(dimethylamino)tert-butoxymethane. Substitution of the dimethylamino group by different amines provided the corresponding sugar enamines 3 as (Z) isomers. 2 reacted with hydrazine hydrate to furnish the pyrano[3,4-c]pyrazole 4. Treatment of 2 with acetamidine hydrochloride, benzamidine hydrochloride, S-methylisothiouronium methylsulfate and guanidine carbonate, respectively, in the presence of bases yielded the pyrimidoanellated pyranosides 5. Reaction of 2, ethyl 2-cyano-acetimidate hydrochloride 7 and sodium hydride afforded a mixture of a pyrido- and pyranoanellated pyranoside 9 and 10, respectively.
Carbohydrate Research | 1989
Klaus Peseke; Horst-Dieter Ambrosi; Manfred Michalik
Abstract The reaction of methyl 2,3,4-tri- O -acetyl-6-deoxy-6-nitro-α- d -glucopyranoside and 3,4,5,7-tetra- O -acetyl-2,6-anhydro-1-deoxy-1-nitro- d - glycero - l - manno -heptitol with carbon disulfide, methyl iodide, and sodium hydride gave methyl 2,3,4-di- O -acetyl-6,7-dideoxy-7,7-bis(methylthio)-6-nitro-α- d - gluco -hept-6-enopyranoside ( 3 ) and 4,5,6,8-tetra- O -acetyl-3,7-anhydro-2-deoxy-2-nitro- d - glycero - l - manno -oct-1-enose dimethyl dithioacetal, respectively. Substitution reactions of 3 were investigated.
Journal of Carbohydrate Chemistry | 2001
Ivette García; Holger Feist; Roberto Cao; Manfred Michalik; Klaus Peseke
Treatment of 2-(2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl)ethanal (1a) and 2-(2,3,4,6-tetra-O-acetyl-α-D-galactopyranosyl)ethanal (1b) respectively with malononitrile in the presence of silica gel provided the corresponding 4-[2,3,4,6-tetra-O-acetyl-α-D-glycopyranosyl]-2-cyanocrotononitriles (2a) and (2b). Starting from 2a and 2b, respectively, cyclizations with sulfur and triethylamine yielded 5-[2,3,4,6-tetra-O-acetyl-α-D-glycopyranosyl]-2-aminothiophene-3-carbonitriles (3a) and (3b). Further cyclizations could be achieved by utilizing of triethyl orthoformate/ammonia to furnish the 6-(α-D-glycopyranosyl)thieno[2,3-d]pyrimidine-4-amines 4a and 4b.
Journal of Carbohydrate Chemistry | 1999
Mario Gomez; José Quincoces; Klaus Peseke; Manfred Michalik; Helmut Reinke
ABSTRACT 1,6-Anhydro-2-(dicyanomethylene)-2,3-dideoxy-4-S-ethyl-4-thio-β-D-erythro-hexopyranose (1) reacted with tosyl azide or sulfur and triethylamine to furnish the 5-aza-10, 11-dioxatricyclo[6.2.1.02,6]undeca-2(6),3-diene-3-carbonitrile 2 and the 10,11-dioxa-5-thiatricyclo[6.2.1.02,6]undeca-2(6),3-diene-3-carbonitrile 3, respectively. The reactions of 1 with arylisothiocyanates furnished the 11,12-dioxa-5-thiatricyclo[7.2.1.02,7]dodeca-2(7),3-diene-3-carbonitriles 4 and 5. 3 underwent cyclization with triethyl orthoformate and ammonia or hydrazine hydrate to afford the 5,7-diaza-14,15-dioxa-9-thiatetracyclo[10.2.1.02,10.03.8]pentadecatetra(tri)enes 7 and 8, respectively.
Journal of Organometallic Chemistry | 1998
Ildikó Rietz; Eckhard Popowski; Helmut Reinke; Manfred Michalik
Abstract The bis(trimethylsilyl)amino-substituted chlorosilanes [(Me3Si)2N]Me2−nPhnSiCl (1: n=0, 2: n=1, 3: n=2) were allowed to react with lithium metal in tetrahydrofuran. 1 slowly reacts at room temperature to the homocoupling product {[(Me3Si)2N]Me2Si}2 (4). An equimolar mixture of 1 and Me3SiCl gives 4 and the cross-coupling product [(Me3Si)2N]Me2Si–SiMe3 (5). The reaction of 2 at −78°C leads to formation of bis(trimethylsilyl)aminosilyllithium [(Me3Si)2N]MePhSiLi (6), which reacts with Me3SiCl and 2 resp. to the corresponding disilanes [(Me3Si)2N]MePhSi–SiMe3 (7) and {[(Me3Si)2N]MePhSi}2 (8). 6 undergoes partially self-condensation at −40 and 0°C and the disilanyllithium [(Me3Si)2N]MePhSi–SiMePhLi (9) is formed. 3 reacts rapidly at 0 and −20°C to give the silyllithium [(Me3Si)2N]Ph2SiLi (12). Treatment of 12 with Me3SiCl and 3 resp. affords the disilanes [(Me3Si)2N]Ph2Si–SiMe3 (13) and {[(Me3Si)2N]Ph2Si}2 (14). The disilane R[(Me3Si)2NMeSi–SiMe3 (11) (R=3,4,5,6-tetrakis(trimethylsilyl)cyclohex-1-enyl) is obtained by reaction of a mixture of 2 and Me3SiCl in molar ratio 1:5 with 6 equivalents of lithium in THF. The crystal structure of 11 is reported. Zusammenfassung Die bis(trimethylsilyl)amino-substituierten Chlorsilane [(Me3Si)2N]Me2−nPhnSiCl (1: n=0, 2: n=1, 3: n=2) wurden mit Lithium in Tetrahydrofuran umgesetzt. 1 reagiert langsam bei Raumtemperatur zum Homokupplungsprodukt {[(Me3Si)2N]Me2Si}2 (4). Ein aquimolares Gemisch von 1 und Me3SiCl ergibt neben 4 auch das Kreuzkupplungs-produkt [(Me3Si)2N]Me2Si–SiMe3 (5). Die Reaktion von 2 bei −78°C fuhrt zum Bis(trimethylsilyl)aminosilyllithium [(Me3Si)2N]MePhSiLi (6), bei dessen Umsetzung mit Me3SiCl bzw. 2 die entsprechenden Disilane [(Me3Si)2N]MePhSi–SiMe3 (7) und {[(Me3Si)2N]MePhSi}2 (8) entstehen. Bei −40 und 0°C unterliegt 6 partiell einer Eigenkondensation, und das Disilanyllithium [(Me3Si)2N]MePhSi–SiMePhLi (9) wird gebildet. 3 reagiert bei 0 und −20°C schnell zum Silyllithium [(Me3Si)2N]Ph2SiLi (12). Die Reaktion von 12 mit Me3SiCl bzw. 3 ergibt die entsprechenden Disilane [(Me3Si)2N]Ph2Si–SiMe3 (13) und {[(Me3Si)2N]Ph2Si}2 (14). Bei der Reaktion eines Gemisches von 2 und Me3SiCl im Molverhaltnis 1:5 mit 6 Aquivalen-ten Lithium in THF entsteht das Disilan-R[(Me3Si)2NMeSi–SiMe3 (11) (R=3,4,5,6-Tetrakis(trimethylsilyl)cyclohex-1-enyl). Die Kristallstruktur von 11 ist beschrieben.
Journal of Carbohydrate Chemistry | 2004
Reinaldo Molina Ruiz; Iran Otero Martinéz; Manfred Michalik; Helmut Reinke; José Quincoces Suarez; Klaus Peseke
Abstract Isopropyl 6‐O‐acetyl‐3‐deoxy‐4‐S‐ethyl‐4‐thio‐α‐D‐threo‐hexopyranosid‐2‐ulose (3) was converted to the corresponding 3‐[bis(methylthio)methylene] derivative 4 with a push–pull activated C–C double bond. Treatment of 4 with hydrazine and methylhydrazine afforded the pyrano[3,4‐c]pyrazol‐5‐ylmethyl acetates 5a and 5b, respectively. Desulfurization of compound 4 with sodium boron hydride yielded the 3‐[(methylthio)methylene]hexopyranosid‐2‐ulose 7. Compound 7 was reacted with amines to furnish 3‐aminomethylene‐hexopyranosid‐2‐uloses 8, 9. Reaction of 7 with hydrazine hydrate, hydrazines, hydroxylamine, and benzamidine afforded the pyrazolo, isoxazalo, and pyrimido anellated pyranosides (10–13). #Dedicated to Professor Dr. Günther Oehme on the occasion of his 65th birthday.