| 81 | Author
| Ulrike Holzgrabe, Willy Friedrichsen, Rl-FH. Esse | Requires 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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| default:Reihe_B/46/ZNB-1991-46b-1237.pdf | | | Identifier
| ZNB-1991-46b-1237 | | | Volume
| 46 | |
83 | Author
| Hermann Irngartingera, Jochen Lichtenthälera, Dieter Fenskeb, Gerhard Baumb | Requires 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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| default:Reihe_B/48/ZNB-1993-48b-1411.pdf | | | Identifier
| ZNB-1993-48b-1411 | | | Volume
| 48 | |
84 | Author
| FrankB. Itterer, S. Tefan, K. Ucken, KlausP. Langhans, O. Th, Ar Stelzer, W. S. Sheldrick | Requires 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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| default:Reihe_B/49/ZNB-1994-49b-1223.pdf | | | Identifier
| ZNB-1994-49b-1223 | | | Volume
| 49 | |
85 | Author
| Akinori Shiotani | Requires 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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| default:Reihe_B/49/ZNB-1994-49b-1731.pdf | | | Identifier
| ZNB-1994-49b-1731 | | | Volume
| 49 | |
86 | Author
| RolfW. Saalfrank3 ', BerndH. Örner1, Stephan Recka, Jochen Nachtraba, Eva-Maria Petersb, Karl Petersb, Hans Georg Von Schneringb | Requires 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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| default:Reihe_B/51/ZNB-1996-51b-1084.pdf | | | Identifier
| ZNB-1996-51b-1084 | | | Volume
| 51 | |
87 | Author
| FredR. Oschea, G. Ernot, H. Eckm, Anna, FrankW. Ellerb, Ekkehard Fluck0 | Requires 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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| default:Reihe_B/51/ZNB-1996-51b-1725.pdf | | | Identifier
| ZNB-1996-51b-1725 | | | Volume
| 51 | |
88 | Author
| Phosphonio-Substituted Tetrahydro-, -Diphosphinines, -Azaphosphinines, Georg Jochem, Martin Schm, HeinrichN. Öth ', Alfred Schmidpeter | Requires 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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| default:Reihe_B/51/ZNB-1996-51b-1761.pdf | | | Identifier
| ZNB-1996-51b-1761 | | | Volume
| 51 | |
89 | Author
| Lothar Beyer | Requires 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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| default:Reihe_B/52/ZNB-1997-52b-0620.pdf | | | Identifier
| ZNB-1997-52b-0620 | | | Volume
| 52 | |
90 | Author
| A. Rto, M. Aaninena, R. Ené, T. B. Oeré, Tristram Chivers0, M. Asood Parvezc | Requires 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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| default:Reihe_B/54/ZNB-1999-54b-1170.pdf | | | Identifier
| ZNB-1999-54b-1170 | | | Volume
| 54 | |
91 | Author
| R. Balamurali, K.J Rajendra Prasad | Requires 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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| default:Reihe_B/54/ZNB-1999-54b-1618_n.pdf | | | Identifier
| ZNB-1999-54b-1618_n | | | Volume
| 54 | |
92 | Author
| Helm Ut Besl, Andreas Bresinsky, RupertH. Errm, Ann, Wolfgang Steglich | Requires 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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| default:Reihe_C/35/ZNC-1980-35c-0824_n.pdf | | | Identifier
| ZNC-1980-35c-0824_n | | | Volume
| 35 | |
94 | Author
| WalterA. Priitz | Requires 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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| default:Reihe_C/39/ZNC-1984-39c-0725.pdf | | | Identifier
| ZNC-1984-39c-0725 | | | Volume
| 39 | |
95 | Author
| Kimiaki Yamano, Haruhisa Shirahama | Requires 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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| default:Reihe_C/49/ZNC-1994-49c-0707.pdf | | | Identifier
| ZNC-1994-49c-0707 | | | Volume
| 49 | |
96 | Author
| Jürg En, Jacob, G. Ottfried, R. Aab | Requires 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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| default:Reihe_C/51/ZNC-1996-51c-0743.pdf | | | Identifier
| ZNC-1996-51c-0743 | | | Volume
| 51 | |
97 | Author
| Christine Kamperdick3, Günter Adam3, NguyenHong Vanb, TranVan Sungb | Requires 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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| default:Reihe_C/52/ZNC-1997-52c-0295.pdf | | | Identifier
| ZNC-1997-52c-0295 | | | Volume
| 52 | |
98 | Author
| M. Veith | Requires cookie* | | Title
| Cyclische Diazastannylene, II 1 Intermolekulare Lewis-Säure-Base-Addukte bei 1.3.2.4A 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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| default:Reihe_B/33/ZNB-1978-33b-0001.pdf | | | Identifier
| ZNB-1978-33b-0001 | | | Volume
| 33 | |
99 | Author
| George Sosnovsky, Maria Konieczny | Requires 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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| default:Reihe_B/33/ZNB-1978-33b-0792.pdf | | | Identifier
| ZNB-1978-33b-0792 | | | Volume
| 33 | |
100 | Author
| MohamedHilmy Elnagdi, Mohamed Ezzat, KamalUsef Kandeel, Sadek | Requires 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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| default:Reihe_B/34/ZNB-1979-34b-0275.pdf | | | Identifier
| ZNB-1979-34b-0275 | | | Volume
| 34 | |
|