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81Author    Ulrike Holzgrabe, Willy Friedrichsen, Rl-FH. EsseRequires cookie*
 Title    Keto-Enol-Tautomerism and Configurational Isomerism of 2,6-Disubstituted 4-Piperidone-3,5-dicarboxylates [1]  
 Abstract    The dialkyl 2,6-dialkylsubstituted 4-piperidone-3,5-dicarboxylates were synthesized by a M annich procedure. Depending on the substitution at the nitrogen keto-enol-tautomerism and a configurational isomerism at C 2 is observed. The structure o f the N-substituted piperi-done 24 E (C 18H 29N 0 5) has been determined by X-ray analysis: it is characterized by an enol structure o f the /?-ketoester and an axial position o f the alkyl group at C 2 and an equatorial one o f the alkyl group at C 6. The O -H -O hydrogen bond shows characteristic values o f a strong hydrogen bond. The N-unsubstituted piperidones adopt a ketone structure with the all-equatorial position o f all substituents. This stereochemistry is confirmed for other enolic and ketone analogues by N M R spectroscopic methods. To work out the reason for the different thermodynamic stabilities o f the different stereochemical structures o f N-substituted and N-unsubstituted piperidones, various semiempirical calculations were done for series o f simple pairs o f carbonyl/enol tautomers, substituted acetoacetates, oxoglutarate as well as o f syste­ matically varied substituted cyclohexanone, 4-oxacyclohexanone and 4-piperidone deriva­ tives. 
  Reference    Z. Naturforsch. 46b, 1237—1250 (1991); received Novem ber 2 1990 
  Published    1991 
  Keywords    2, 6-Disubstituted 4-Piperidone-3, 5-dicarboxylates, High-resolution N M R, X-Ray, Theoretical Calculations 
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 TEI-XML for    default:Reihe_B/46/ZNB-1991-46b-1237.pdf 
 Identifier    ZNB-1991-46b-1237 
 Volume    46 
82Author    Thomas Strelow, Jürgen Voss, Gunadi AdiwidjajaRequires cookie*
 Title    Preparation and Structure of Ethyl 4-Bromo-2-(diphenylmethyIene)- 3-oxo-5,5-diphenyl-4-pentenoate  
  Reference    Z. Naturforsch. 47b, 1007—7 (1992); eingegangen am 23. Dezember 1991 
  Published    1992 
  Keywords    2, 4-D im ethylene-l, 3-cyclobutandione, D ouble-bond Splitting, Crystal Structure 
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 TEI-XML for    default:Reihe_B/47/ZNB-1992-47b-1007.pdf 
 Identifier    ZNB-1992-47b-1007 
 Volume    47 
83Author    Hermann Irngartingera, Jochen Lichtenthälera, Dieter Fenskeb, Gerhard BaumbRequires cookie*
 Title    Synthesen und Strukturen von 2,5-Bis(2-arylvinyl)-l,4-benzochinonen und deren photochemisches Verhalten im Kristall Syntheses and Crystal Structures of 2,5-Bis(2-arylvinyl)-l,4-benzoquinones and their Photochemical Reactivity in the Crystalline State  
  Reference    Z. Naturforsch. 48b, 1411—1418 (1993); eingegangen am 14. Mai 1993 
  Published    1993 
  Keywords    2, 5-D istyryl-l, 4-benzoquinones, Synthesis, Crystal Structure, Solid State Photochemistry 
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 TEI-XML for    default:Reihe_B/48/ZNB-1993-48b-1411.pdf 
 Identifier    ZNB-1993-48b-1411 
 Volume    48 
84Author    FrankB. Itterer, S. Tefan, K. Ucken, KlausP. Langhans, O. Th, Ar Stelzer, W. S. SheldrickRequires cookie*
 Title    Fragmentierung und Zyklisierung disekundärer Methylenbisphosphane mit sperrigen aromatischen Resten in Fe3-und Ru3-Clustern  
 Abstract    L inear O ligophosphaalkanes, X X V II [1] F rag m en tatio n and Cyclization of D isecondary M ethylenebisphosphanes with Bulky A ro m atic Substituents in F e3 and R u 3 C lusters 
  Reference    Z. Naturforsch. 49b, 1223—1238 (1994); eingegangen am 8. März 1994 
  Published    1994 
  Keywords    D isecondary M ethylenebisphosphanes, Bulky Aromatic Substituents, Phosphinidene Fragmentation, Cyclization, 2, 3-Dihydrobenzo[b]phospholes 
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 TEI-XML for    default:Reihe_B/49/ZNB-1994-49b-1223.pdf 
 Identifier    ZNB-1994-49b-1223 
 Volume    49 
85Author    Akinori ShiotaniRequires cookie*
 Title    Die Pd-katalysierte oxidative Kupplungsreaktion von Methylbenzoesäuremethylester The Pd-Catalyzed Oxidative Coupling Reaction of Methyl Methylbenzoates  
 Abstract    The Pd-catalyzed oxidative coupling reaction of methyl o-toluate gives, in the presence of a Pd/l,10-phenanthroline(phen)/Cu catalyst, exclusively, the para-linked biphenyldicarboxy-lates 1, 2, and 3. On the other hand, the meta-linked biphenyldicarboxylates 4 and 5, were predominantly formed in a catalyst system of Pd/2,4-pentanedione(acacH)/Cu, and under similar conditions 6 and 7 were also obtained from the coupling reaction of methyl m-toluate and methyl p-toluate, respectively. A reaction scheme has been proposed. 
  Reference    Z. Naturforsch. 49b, 1731—1736 (1994); eingegangen am 21. April 1994 
  Published    1994 
  Keywords    Coupling Reaction, Steric Influence, Palladium, 1, 10-Phenanthroline, 2, 4-Pentanedione 
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 TEI-XML for    default:Reihe_B/49/ZNB-1994-49b-1731.pdf 
 Identifier    ZNB-1994-49b-1731 
 Volume    49 
86Author    RolfW. Saalfrank3 ', BerndH. Örner1, Stephan Recka, Jochen Nachtraba, Eva-Maria Petersb, Karl Petersb, Hans Georg Von SchneringbRequires cookie*
 Title    Synthese und Umsetzungen von 4-Acyl/Carbamoyl-N-aryl-3-chloro- pyrrol-2,5-dionen: Kristallstruktur eines auf Wasserstoffbrückenbindungen basierenden supramolekularen Bandes [1] Synthesis and Reactions of 4-Acyl/Carbamoyl-N-aryl-3-chloro-pyrrol-2,5-diones: Crystal Structure of a Supramolecular Ribbon Based on Hydrogen Bonds [ 1]  
  Reference    Z. Naturforsch. 51b, 1084—1098 (1996); eingegangen am 14. August 1995 
  Published    1996 
  Keywords    2, 3-Dioxo-2, 3-dihydrofurans, Pyrrol-2, 5-diones, Intermolecular H-Bridges, X-Ray 
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 TEI-XML for    default:Reihe_B/51/ZNB-1996-51b-1084.pdf 
 Identifier    ZNB-1996-51b-1084 
 Volume    51 
87Author    FredR. Oschea, G. Ernot, H. Eckm, Anna, FrankW. Ellerb, Ekkehard Fluck0Requires cookie*
 Title    Ein neuer Heterocyclus  
 Abstract    , 2A3,4A5-[l,2,4]-O xadiphosphinin (2), als Ligand eines zw eikernigen Eisenkom plexes A New H eterocycle, 2A3,4A5-[l,2,4]-O xadiphosphinine (2), as L igand o f a Binuclear Iron C om plex Preparation and properties of a coordination compound are described, in which a carbonyl group in bis[(dicarbonyl)(/;;i-cyclopentadienyl)iron] is substituted by hitherto unknown octa-Af-methyl-2A',4A:i-[l,2,4]-oxadiphosphinine-2,4,4,6-tetramine (2). The 'H , '1P, and l3C NMR spectra are recorded and discussed in detail. The molecular structure of the iron complex 4 is described and interpreted. 
  Reference    Z. Naturforsch. 51b, 1725—1731 (1996); eingegangen am 27. Juni 1996 
  Published    1996 
  Keywords    [l, 2, 4]-Oxadiphosphinine, Binuclear Iron Complex, NMR Spectra, X-Ray 
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 TEI-XML for    default:Reihe_B/51/ZNB-1996-51b-1725.pdf 
 Identifier    ZNB-1996-51b-1725 
 Volume    51 
88Author    Phosphonio-Substituted Tetrahydro-, -Diphosphinines, -Azaphosphinines, Georg Jochem, Martin Schm, HeinrichN. Öth ', Alfred SchmidpeterRequires cookie*
 Title    Phosphonio-substituierte Tetrahydro-l,3-diphosphinine un(j Tetrahy dro-1,2,6-azad i phospli in i ne  
 Abstract    The bis(triphenylphosphonio)propenide cation 1 provides two reactive CH sites in 1,3-position and can be condensed with the bis(dichlorophosphanyl)methylene triphenylphos-phorane 2 or the bis(dichlorophosphanyl)aniline 3 to form cationic six-membered rings: A tetrahydro-1,3-diphosphinine (4) with three phosphonio or phosphoranediyl substituents in 2,4,6-position and a tetrahydro-1,2,6-azadiphosphinine (5) carrying two such substituents in 3,5-position. The bromide of the latter was used for an X-ray structure analysis. The P111 ring members of the cations 4 and 5 can be oxidized in two steps by elemental sulfur to give the monothioxo and dithioxo derivatives 6. 7 and 8, 9. respectively. A crystal of the mixed chloride/bromide of 8 was used for another X-ray structure analysis. 
  Reference    Z. Naturforsch. 51b, 1761—1767 (1996); eingegangen am 16. August 1996 
  Published    1996 
  Keywords    Dichlorophosphanyl Ylides and Amines, Cyclocondensation, Phosphorus Heterocycles, 1, 3-Diphosphinines, 1, 2, 6-Azadiphosphinines 
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 TEI-XML for    default:Reihe_B/51/ZNB-1996-51b-1761.pdf 
 Identifier    ZNB-1996-51b-1761 
 Volume    51 
89Author    Lothar BeyerRequires cookie*
 Title    Substituierte l,2,4-Thiadiazolium-dichloroaurate(I) und -tetra- chloroaurate(III) als Reaktionsprodukte von N-Thiocarbamoyl- benzamidinen mit TetrachIorogold(III)-Verbindungen  
 Abstract    Substituted 1,2,4-T hiadiazolium dichloroaurates(I) and -tetrachloroaurates(III) as Products o f the R eaction o f N -T hiocarbam oyl-benzam idines w ith Tetrachlorogold(III) Com pounds U w e Schröder3, R ainer R ichter3, Jürgen H artung3, U lrich A bram b, 
  Reference    Z. Naturforsch. 52b, 620—628 (1997); eingegangen am 12. März 1997 
  Published    1997 
  Keywords    1, 2, 4-Thiadiazoliumchloroaurates(I/III), Synthesis, X-Ray, EM Spectra, N-Thiocarbamoylbenzamidines 
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 TEI-XML for    default:Reihe_B/52/ZNB-1997-52b-0620.pdf 
 Identifier    ZNB-1997-52b-0620 
 Volume    52 
90Author    A. Rto, M. Aaninena, R. Ené, T. B. Oeré, Tristram Chivers0, M. Asood ParvezcRequires cookie*
 Title    Preparation and X-Ray Structure of 4-N,N'-Bis(trimethylsilyl)- amino-3,5-diisopropylphenylselenium Trichloride  
 Abstract    The reaction of SeCU or SeCF with /V,/V'-bis(trimethylsilyl)-2,6-diisopropylaniline occurs not at the nitrogen atom but by electrophilic aromatic substitution at C-4 of the phenyl ring to give [(CH3)3Si]2NC6 H2('Pr:)SeCl3, which crystallizes as the chloro-bridged dimer in the triclinic system, space group P i, a -10.2598(17), b = 13.665(3), c = 9.7838(10) A, a = 90.056(13), ß = 102.439(11), 7 = 70.922(14)°, V = 1262.3(4) A \ Z = 1. The dimer contains an essentially planar CUSe^-Cl^SeCU unit, with trans apical (Me3SihNC6H2('Pr)2 groups, resulting in approximately square pyramidal geometry at Se. The bridging Se-Cl distances are unequal at 2.587(2) and 2.749(2) A. 
  Reference    Z. Naturforsch. 54b, 1170—1174 (1999); received April 22 1999 
  Published    1999 
  Keywords    Crystal Structure, 2, 6-Diisopropylaniline, Aryl Selenium Trichloride, Bridging Chloride, NMR Data 
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 TEI-XML for    default:Reihe_B/54/ZNB-1999-54b-1170.pdf 
 Identifier    ZNB-1999-54b-1170 
 Volume    54 
91Author    R. Balamurali, K.J Rajendra PrasadRequires cookie*
 Title    A Facile Synthesis of Quino[2,3-fl]carbazoles  
 Abstract    Condensation of l-oxo-l,2,3,4-tetrahydrocarba-zoles la-e and o-aminoacetophenone 2 under acid catalysis afforded a new class of quino[2,3-a]car-bazoles 3a-e in good yields. A plausible mecha­ nism for the product formation is also proposed. 
  Reference    Z. Naturforsch. 54b, 1618—1620 (1999); received June 14 1999 
  Published    1999 
  Keywords    l-Oxo-l, 2, 34-tetrahydrocarbazole, o-Amino-acetophenone Condensation, Cyclisation, Aerial Oxidation 
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 TEI-XML for    default:Reihe_B/54/ZNB-1999-54b-1618_n.pdf 
 Identifier    ZNB-1999-54b-1618_n 
 Volume    54 
92Author    Helm Ut Besl, Andreas Bresinsky, RupertH. Errm, Ann, Wolfgang SteglichRequires cookie*
 Title    Cham onixin and Involutin, two Chemosystematical- ly Interesting Cyclopentanediones from Gyrodon livi­ dus (Boletales) [1]  
 Abstract    The sporophores of Gyrodon lividus contain (—)-cha-monixin and (-)-involutin, indicating the close relation­ ship of Gyrodon to the Paxillaceae and Gyroporus. 
  Reference    Z. Naturforsch. 35c, 824—825 (1980); received May 23 1980 
  Published    1980 
  Keywords    Gyrodon, Boletales, Chamonixin, Involutin, 2, 5-Diarylcy-clopentane-1, 3-diones, Chemosystematics 
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 TEI-XML for    default:Reihe_C/35/ZNC-1980-35c-0824_n.pdf 
 Identifier    ZNC-1980-35c-0824_n 
 Volume    35 
93Author    R. Schmitt, H. SandermRequires cookie*
 Title    Specific Localization of /J-D-Glucoside Conjugates of 2,4-Dichlorophenoxyacetic Acid in Soybean Vacuoles  
  Reference    Z. Naturforsch. 37c, 772—777 (1982); received May 17 1982 
  Published    1982 
  Keywords    2, 4-Dichlorophenoxyacetic Acid, Glycine m ax L, Plant Cell Suspension Culture, Vacuole, /?-ü-Glucosides 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0772.pdf 
 Identifier    ZNC-1982-37c-0772 
 Volume    37 
94Author    WalterA. PriitzRequires cookie*
 Title    Tyrosine Oxidation by NOi in Aqueous Solution  
 Abstract    Nitrogen dioxide, formed by y-radiolysis in deaerated aqueous nitrate/nitrite solutions, is capable of oxidizing Gly-Tyr in favourable competition with the natural decay of N 0 2 by dimerization and disproportionation. 2,2'-Biphenolic tyrosine dimers and nitro-tyrosine were identified spectroscopically as stable products. The results suggest that N 0 2 reacts with the peptide by electron abstraction, generating Gly-Tr phenoxyl radicals (PheO') which terminate by dimerization (2 PheO' -» 2,2'-biphenol) and N 0 2-scavenging (PheO* + N 0 2 -* • Nitro-Tyr). 
  Reference    Z. Naturforsch. 39c, 725—727 (1984); received March 9 1984 
  Published    1984 
  Keywords    2, 2'-Biphenol, Nitrogen Dioxide, Nitro-Tyrosine, Phenoxyl Radical, Tyrosine Oxidation 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0725.pdf 
 Identifier    ZNC-1984-39c-0725 
 Volume    39 
95Author    Kimiaki Yamano, Haruhisa ShirahamaRequires cookie*
 Title    Clitocybe acromelalga  
 Abstract    A new piperidine amino acid, 2,4,5-piperidinetricarboxylic acid (11) was isolated from the poisonous mushroom, Clitocybe acromelalga. The structure determination and its biogenetic potential are discussed. 
  Reference    Z. Naturforsch. 49c, 707 (1994); received July 7/August 15 1994 
  Published    1994 
  Keywords    Clitocybe acromelalga, Toadstool, Piperidine Amino Acid, 2, 4, 5-Piperidinetricarboxylic Acid, Biogenesis 
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 TEI-XML for    default:Reihe_C/49/ZNC-1994-49c-0707.pdf 
 Identifier    ZNC-1994-49c-0707 
 Volume    49 
96Author    Jürg En, Jacob, G. Ottfried, R. AabRequires cookie*
 Title    2,3-Dihydroxy Fatty Acids-Containing Waxes in Storks (C iconiidae)  
 Abstract    Uropygial gland secretions from five out of a total of seven species forming the genus Ciconia (family Ciconiidae; order Ciconiiformes) were found to consist of mixtures of monoester waxes, diester waxes, triester waxes, and triglycerides. Monoester waxes were com­ posed of unbranched fatty acids and alcohols, whereas diester waxes derived from both 2-and 3-hydroxy fatty acids esterified with unbranched alcohols and fatty acids. Interestingly, triester waxes were also found deriving from either 2-hydroxy alkylmalonic acids or from erythro-2,3-dihydroxy fatty acids the latter of which have not yet been found in vertebrates so far. To compare the typical mass spectrometric fragmentation of this class of compounds eryr/?/-o-2,3-dihydroxyhexadecanoic acid has been synthesized. 
  Reference    Z. Naturforsch. 51c, 743—749 (1996); received June 7/July 1 1996 
  Published    1996 
  Keywords    2, 3-Dihydroxy Fatty Acids, Uropygial Gland Secretion, Triester Waxes, Ciconiiform Birds 
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 TEI-XML for    default:Reihe_C/51/ZNC-1996-51c-0743.pdf 
 Identifier    ZNC-1996-51c-0743 
 Volume    51 
97Author    Christine Kamperdick3, Günter Adam3, NguyenHong Vanb, TranVan SungbRequires cookie*
 Title    Chemical Constituents of Madhuca pasquiery  
 Abstract    Four triterpenoids, the scarce nortriterpenoid platanic acid, two flavonoids and 2,4-dihy-droxy phenylacetic acid methyl ester, hitherto unknown as a natural product, were isolated from Madhuca pasquiery. The structures were established by means of mass and NMR spectroscopy. 
  Reference    Z. Naturforsch. 52c, 295 (1997); received D ecem ber 12 1996/February 12 1997 
  Published    1997 
  Keywords    Madhuca pasquiery, 2, 4-Dihydroxy Phenylacetic Acid Methyl E ster, Platanic Acid, Triterpenoids, Flavonoids 
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 TEI-XML for    default:Reihe_C/52/ZNC-1997-52c-0295.pdf 
 Identifier    ZNC-1997-52c-0295 
 Volume    52 
98Author    M. VeithRequires cookie*
 Title    Cyclische Diazastannylene, II 1 Intermolekulare Lewis-Säure-Base-Addukte bei 2 -Diazasilastannetidinen Cyclic Diazastannylenes, II 1 Intermolecular Lewis-Acid-Base Adducts of 1, 3,2,4A 2 -Diazasilastannetidines  
 Abstract    -diazasilastannetidines can be prepared as mono-mers (organyl = <erf-butyl) or dimers (organyl = isopropyl) in nonpolar solvents, depending on the organic nitrogen substituent. The formation of the dimer, which is due to an intermolecular Lewis-acid-base interaction of Sn(II) with nitrogen, can be initiated by solidification. When the tertf-butyl compound is cooled below 0 °C two crystalline modi-fications are found: a monoclinic phase (C 2/c; a= 10.655(5); b = 24.75(1); c = 17.334(9) Ä; ß = 106.9(1)°) and a triclinic phase (P I; a = 10.68(1); b = 13.51(1); c = 12.36(1) A; a = 96.2(1); ß = 102.6(1); y = 118.4(1)°). The crystal structures turn out to be built of dimeric and monomeric units in the first case and presumably only dimeric species in the second case. The isopropyl derivative crystallizes in the space group P 2i/b (a = 10.77(1); b= 12.14(2); c = 11.15(2) A; ß = 120.2(2)°) with only dimeric units being present, as in the liquid. Interrelationships between the three structures are discussed. 
  Reference    (Z. Naturforsch. 33b, 1—6 [1978]; eingegangen am 5. September/6. Oktober 1977) 
  Published    1978 
  Keywords    Diazastannylenes, Solid State, X-ray, Crystal Structure, NMR l, 3-Diorganyl-2, 2-dimethyl-I, 3, 2, 4A 2 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0001.pdf 
 Identifier    ZNB-1978-33b-0001 
 Volume    33 
99Author    George Sosnovsky, Maria KoniecznyRequires cookie*
 Title    Utilization of the Sterically Hindered Base, 4-Hydroxy-2,2,6,6-tetramethylpiperidine, as a Hydrogen Halide Acceptor  
  Reference    Z. Naturforsch. 33b, 792—796 (1978); received March 17 1978 
  Published    1978 
  Keywords    Dehydrobromination, Preparation of Alkenes, Quaternization of Amines, Sterically Hindered Bases, 4-Hydroxy-2, 2, 6, 6-tetramethylpiperidine 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0792.pdf 
 Identifier    ZNB-1978-33b-0792 
 Volume    33 
100Author    MohamedHilmy Elnagdi, Mohamed Ezzat, KamalUsef Kandeel, SadekRequires cookie*
 Title    Reactions with Cyclic Amidenes III: Synthesis of Some New Fused Pyrazole Derivatives  
  Reference    Z. Naturforsch. 34b, 275—279 (1979); received August 28 1978 
  Published    1979 
  Keywords    Diazobetaienes, Dipolarcycloaddition, Pryazolo[4, 3-c]-l, 2, 3, 4-tetrazines, Ethoxycarbonyl Isothiocyanate, X H NMR 
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 TEI-XML for    default:Reihe_B/34/ZNB-1979-34b-0275.pdf 
 Identifier    ZNB-1979-34b-0275 
 Volume    34