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  • Chemistry  (99)
  • Calculations, ab initio  (2)
  • Wiley-Blackwell  (99)
  • 1990-1994  (54)
  • 1985-1989  (26)
  • 1970-1974  (5)
  • 1940-1944  (14)
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  • Wiley-Blackwell  (99)
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  • 1
    Electronic Resource
    Electronic Resource
    Pyrazolo[3,4-d]pyrimidine 2′ -Deoxy- and 2′,3′ -Dideoxyribonucleosides: Studies on the glycosylation of 4-methoxypyrazolo[3,4-d]pyrimidine (1993)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 76 (1993), S. 1450-1458 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The glycosylation of the 4-methoxypyrazolo[3,4-d]pyrimidine (5) anion with 1-halo-2-deoxyribose 6 in MeCN/TDA-1 gives N2-deoxynucleoside 9 (29%) together with N1-isomer 7 (48%) and its anomer 8 (6%) [7]. The α-D-anomer 8 is not formed and the yield of the ß-D-anomer 7 increased to 62% when dimethoyethane is used as solvent and [18]crown-6 as catalyst. Employing 1-halo-2,3-dideoxyribose 10 instead of halogenose 6, the 2′,3′ -didexoynucleosides 12 and 14 were formed which desilylated (→ 1b and 2b) and converted into the ddI and ddA derivatives 3b (c7z8Idd), 15b (c7z8Add), and 17 (c7z8A′dd). Contrary to 7-deazapurine nucleotides, the triphosphates of 3b and 15b showed on appreciable activity against HIV-reverse transcriptase.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19930760405
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  • 2
    Electronic Resource
    Electronic Resource
    Alkylchrom- und Alkylmangan-Reagenzien, IV. Über die Aldehyd- und cheleselektive Alkylierung organischer Carbonylverbindungen mit Monoalkylchrom(III)-Reagenzien (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 157-162 
    Details
    ISSN: 0009-2940
    Keywords: Chromium organo compounds ; Chemoselectivity ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkylchromium and Alkylmanganese Reagents, IV.  -  On the Aldehyde and Cheleselective Alkylation of Organic Carbonyl Compounds with Monoalkylchromium(III) ReagentsMonoalkylchromium(III) reagents, prepared in crystalline form or in solution, alkylate aldehydes but normally not ketones. Ketones with a basic group (HO, MeO, Me2N) in α- or β-position are methylated by MeCrCl2(thf)3, allowing the highly selective («cheleselective») methylation of such ketones in the presence of normal ketones.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250126
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  • 3
    Electronic Resource
    Electronic Resource
    Cycloadditionsreaktionen von Heterocumulenen, XXIX. Reaktion von Thioketenen mit Isocyanaten (1988)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 689-699 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cycloaddition Reactions of Heterocumulenes, XXIX.  -  Reactions of Thioketenes with IsocyanatesThe [2 + 2] cycloaddition of thioketenes 1a-f to isocyanates 2a-f yields 4-thioxo-2-azetidinones 3 as main products, which may isomerize to 4-imino-2-thietanones 5. In competing reactions, 2,4-azetidinediones 8, N-sulfonylamides 9, and 3H-1,2,4-dithiazoles 15 are formed. Thioketenes 1 react with chlorosulfonyl isocyanate (20b) to give N-unsubstituted 4-thioxo-2-azetidinones 22. Depending on the thioketene 1 and the reaction conditions, compounds 23-26 also result. The constitutions of 15b and 23a were determined by X-ray structural analyses.
    Notes: Die [2 + 2]-Cycloaddition der Thioketene 1a-f an die Isocyanate 2a-f liefert als Hauptprodukt 4-Thioxo-azetidinone 3, die sich zu 4-Imino-2-thietanonen 5 isomerisieren können. In Konkurrenzreaktionen werden 2,4-Azetidindione 8, N-Sulfonylamide 9 und 3H-1,2,4-Dithiazole 15 gebildet. Mit Chlorsulfonylisocyanat (20b) reagieren die Thioketene 1 zu N-unsubstituierten 4-Thioxo-2-azetidinonen 22. Je nach Thioketen 1 und Reaktionsführung resultieren auch die Verbindungen 23-26. Die Konstitution von 15b und 23a wurde durch Röntgenstrukturanalyse bestimmt.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19881210416
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  • 4
    Electronic Resource
    Electronic Resource
    1,3-Diazabutadiene: Kristallstruktur, quantenmechanische Berechnungen und spektroskopische Untersuchung (1989)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 1705-1710 
    Details
    ISSN: 0009-2940
    Keywords: 1,3-Diazabutadienes ; ab initio calculations ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,3-Diazabutadienes: Crystal-Structure Analysis, Quantum-Mechanical Calculations, and Spectroscopic InvestigationThe X-ray analysis of derivative 3a (available from the corresponding amidine and aldehyde by titanium tetrachloride assisted condensation) shows, that the substituent at the nitrogen atom N1 prefers the (Z)position. The heterobutadiene chain is strongly twisted [Θ(N2—C7—N1—C8) = 109.7°], indicating only weak conjugative interactions between the two C=N units. The dynamic properties of 1,3-diazabutadiene (4) (N-methyleneformamidine) were simulated by ab initio calculations (3-21G, MP2/6-31G*). The global minimum corresponds to the s-trans isomer 4a with (Z) configuration at N1 = C2; a gauche form (local minimum) 4c is slightly higher in energy. For the (E)-N1=C2 isomers, gauche structure 4d is lowest in energy, the s-trans form 4b is less favourable by 2-3 kcal/mol. The calculated rotational barriers (2-7 kcal/mol) are similar to those of butadiene. Inversion processes also have low barriers: Transition structures with linear, sphybridized nitrogen atoms N3 and orthogonal positions of the N3=C4 unit were found (Erel ≍ 20 kcal/mol). IR1H-, 13C-NMR, and UV data are given and compared with the results of the structural investigations.
    Notes: Die Kristallstrukturbestimmung des durch Kondensation des entsprechenden Amidins unter Aldehyds Titantetrachlorid-Zusatz erhältlichen Derivates 3a zeigt, daß sich der Substituent am Stickstoff-Atom N1 in der (Z)-Position befindet. Das Heterobutadien-Gerüst fällt durch seinen großen Torsionswinkel [Θ(N2—C7—N1—C8) = 109.7°] auf und läßt auf nur schwache konjugative Wechselwirkungen zwischen den beiden C=N-Einheiten schließen. Die dynamischen Eigenschaften von 1,3-Diazabutadien (4) (N-Methylenformamidin) wurden durch ab-initio-Berechnungen (3-21 G, MP2/6-31G*) simuliert. Demnach ist die günstigste Struktur die s-trans-Form 4a mit (Z)-Konfiguration an N1 = C2; daneben existiert ein gauche-Minimum 4c mit geringfügig höherer Energie. Für die (E)-N1=C2-Konfiguration ist die gauche-Form 4d am energieärmsten, die s-trans-Struktur 4b entspricht einem lokalen Minimum (Erel ≍ 2-3 kcal/mol). Die berechneten Rotationsbarrieren (2-7 kcal/mol) sind denen von Butadien vergleichbar. Auch Inversionsprozesse an N3 haben niedrige Barrieren: Es konnten Übergangszustände mit linearem, sphybridisiertem Stickstoff-Atom N3 und orthogonaler Stellung der N3=C4-Einheiten ermittelt werden (Erel ≍ 20 kcal/mol). IR1H-, 13C-NMR- und UV-Daten werden zugeordnet und mit den Strukturergebnissen verglichen.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19891220917
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesen und Reaktionen acyclischer fluororganischer Thiocarbenium-IonenHerrn Prof. Dr. W. Sawodny zum 60. Geburtstag gewidmet. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 597-603 
    Details
    ISSN: 0009-2940
    Keywords: (Trifluoromethylthio)carbon ; Carbenium ions ; One-electron oxidation ; Superacidic systems ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses and Reactions of Fluoroorganic Acyclic Thiocarbenium IonsHerrn Prof. Dr. W. Sawodny zum 60. Geburtstag gewidmet.Arsenic pentafluoride oxidizes (F3CS)4C (1) but not (F3CS)2C = C(SCF3)2 (2) to yield the stable salt (F3CS)3C+AsF-6 (3). It reacts with halide ions to form (F3CS)3CX (3a-c, X = F, Cl, Br). Iodide is oxidized to iodine with formation of (F3CS)3CC(SCF3)3 (4) which reacts with nitrogen dioxide to give (F3CS)3CNO2 (3e). - (F3CS)3C+AsF-6 (3) removes from (F)-SCF3 (5a) a ring-bound fluorine atom to afford (F3CS)3CF and -SCF3]+AsF-6 (5). When (F3CS)3CCl (3b) is treated with AsF5, 3 and [(F3CS)2-CCl]+AsF-6 (6) are formed in a 2:1 molar ratio. The latter reacts with F- or Cl- to give (F3CS)2CClX (6a,b; X = F, Cl). AsF5 is capable of abstracting a fluoride ion from (F3CS)3 - n Cln,CF only if n = 0 or 1. For n = 2 no similar reaction takes place, but with AlCl3 in BCl3 halogen exchange to F3CSCCl3 (7b) is observed. - Alkylation of (F3CS)2C=S (8) with H3CF/AsF5 yields [(F3CS)2CSCH3]+AsF-6 (9), which adds a fluoride ion to give (F3CS)2(H3CS)CF (9a). The molecular structures of (F3CS)2C = C(SCF3)2 (2) and (F3CS)3CC(SCF3)3 (4) have been determined by X-ray diffraction methods.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270403
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  • 6
    Electronic Resource
    Electronic Resource
    N,N-Bis(trimethylsilyl)ynamines: Cycloaddition Reactions with Dimethyl Acetylenedicarboxylate and Ketenes (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1287-1293 
    Details
    ISSN: 0009-2940
    Keywords: Ynamines, N,N-bis(trimethylsilyl)- ; Cycloaddition reactions ; Cyclopropenes ; Furans ; Ketenes ; Cyclobutenones ; Allenylcarboxamides ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N,N-Bis(trimethylsilyl)ynamines 1 react with dimethyl acetylenedicarboxylate (2) in a molar ratio of 1:2 to afford 3-cyclopropenylfurans 3. Configuration and conformation of 3a are confirmed by X-ray crystallography. Addition of a further mol of 1 furnishes the fumarates 4. With ketenes 5 (5c, d are prepared in situ) a competition between the formation of cyclic butenone derivatives 6 and allenic imidates 7 is observed, depending on the substitution pattern of 1. After hydrolytic workup, the corresponding amides 10 or the vinylogous amides 9 are obtained in good yield. These experiments indicate that the silylated ynamines 1 show a completely different, more selective reactivity towards dimethyl acetylenedicarboxylate compared to N,N-dialkyl-substituted ynamines, yielding furan derivatives instead of anilines. Towards ketenes, however, a similar cycloaddition reactivity as for N,N-dialkylynamines is observed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270718
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  • 7
    Electronic Resource
    Electronic Resource
    Über das Reaktionsverhalten von 4-Thioxo-2-azetidinonen (1988)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 701-707 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Reactivity of 4-Thioxo-2-azetidinonesBase-catalyzed alcoholysis of the N—S bond in N-sulfonylthioxoazetidinones 1 is a ready process; the resulting sulfonate then alkylates the liberated 2-. Alkylations of 2 under various conditions demonstrate that charge and thermodynamic control favor attack on nitrogen to give 5 rather than reaction on sulfur to give 4. Besides simple alkyl residues (4a-c, 5a-c) also functionalized alkyl (4d, e, g, m, n, o, 5d, e, g, i, m-o), aryl (5p), and acyl groups (5q) can be introduced and addition reactions (5r, s) achieved. Complex hydrides reduce the carbonyl group in 1,5 to yield 8-10, but the C=N+ unit in the salt 6a to furnish β-lactam 11. Annulation of a five-membered ring to give 12 is achieved by 1,3-dipolar cycloaddition of dimethyl fumarate to in-situ generated azomethine ylide 6d.
    Notes: Die basenkatalysierte Alkoholyse der N—S-Bindung in N-Sulfonyl-thioxoazetidinonen 1 tritt leicht ein; der entstehende Sulfonsäureester alkyliert dann das freigesetzte 2-. Unter verschiedenen Bedingungen durchgeführte Alkylierungsreaktionen an 2 zeigen, daß Ladungs- und thermodynamische Kontrolle den Angriff am Stickstoff zu 5 gegenüber der Reaktion am Schwefel zu 4 begünstigen. Neben einfachen Alkyl-Resten (4a-c, 5a-c) lassen sich auch funktionalisierte Alkyl-(4d, e, g, m, n, o, 5d, e, g, i, m-o), Aryl- (5p) und Acyl-Gruppen (5q) einführen sowie Additionsreaktionen (5r, s) erreichen. Komplexe Hydride reduzieren die Carbonyl-Gruppe in 1, 5 zu 8-10, aber den C=N+-Teil im Salz 6a zum β-Lactam 11. Die Anellierung eines Fünfrings zu 12 gelingt über die 1,3-dipolare Cycloaddition von Fumarsäure-dimethylester an das in situ freigesetzte Azomethin-Ylid 6d.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19881210417
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  • 8
    Electronic Resource
    Electronic Resource
    Unsaturated Hetero Chains, II. 1-Oxa-3,5,7-triaza-1,3,5,7-octatetraenes - Syntheses and Structures (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2467-2476 
    Details
    ISSN: 0009-2940
    Keywords: 1-Oxa-3,5,7-triaza-1,3,5,7-octatetraenes ; Ring-chain tautomerism ; Calculations, ab-initio ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three independent routes for the synthesis of the hitherto unknown substituted 1-oxa-3,5,7-triazaoctatetraenes 4 have been developed. Method 1 utilizes N-lithiated imines 1 and 1,3,5-oxadiazinium salts 2 for the synthesis of 4b-e. Method 2 takes advantage of the new 6-alkoxy-1-oxa-3,5-diazahexatrienes 5, which are allowed to react with imino lithium compounds to produce 4f. Method 3 is based on the combination of the lithiated 1,3-diazabutadiene 7 with the N-acylimidate 8 and gives access to 4g-j. Depending on the substitution pattern, the title compounds show ring-chain tautomerism; in the case of the pentaphenyl system, only the triazine derivative 3a is observed. An X-ray analysis of 4f reveals a non-planar structure with (+)-gauche-Z-(-)-gauche-Z-(+)-gauche conformation, resulting from amide-like n/π interactions between C=N-π systems and the lone pair of the adjacent nitrogen atoms. Detailed spectroscopic data for all open-chain and cyclic compounds are given. Quantum mechanical calculations (MP2/6-31G*//6-31G*) of model compounds 13 predict that non-planar isomers with gauche-configurated subunits are favored by more than 8 kcal/mol over a planar all-trans structure as in polyenes. Most planar isomers correspond to low-lying transition states for the rotation around the C-N bonds, but not to local minima, indicating high molecular flexibility of these oligonitrile chains.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261121
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  • 9
    Electronic Resource
    Electronic Resource
    Darstellung und Struktur von 1-Oxa-3,5-diaza-1,3,5-hexatrienen. Die 1-Oxa-3,5-diaza-1,3,5-hexatrien/2H-1,3,5-Oxadiazin-Tautomerie (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 957-967 
    Details
    ISSN: 0009-2940
    Keywords: 1-Oxa-3,5-diaza-1,3,5-hexatrienes ; 2H-1,3,5-Oxadiazines ; 1-Oxa-3,5-diaza-1,3,5-hexatriene - 2H-1,3,5-Oxadiazine tautomerism ; Ring-chain tautomerism ; Calculations, ab initio ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Structures of 1-Oxa-3,5-diaza-1,3,5-hexatrienes. The 1-Oxa-3,5-diaza-1,3,5-hexatriene/2H-1,3,5-Oxadiazine TautomerismReaction of N1-lithio-or N1-trimethylsilyl-substituted imines 1 with N1-acylimidic acid derivatives 2 provides 1-oxa-3,5-diaza-1,3,5-hexatrienes 3 in fair to good yields. Depending on the substitution pattern, the acyclic compounds 3 form an equilibrium with their cyclic tautomers, e.g. 2H-1,3,5-oxadiazines 4. Aromatic substituents at C-6 favor the acyclic form 3, whereas aliphatic groups (e.g. tert1-butyl) lead to the exclusive formation of the ring tautomer 4. For a typical example (3d/4d) the free enthalpy of activation for the ring/chain tautomerism was determined to be ca. 12.5 kcal/mol. Detailed spectroscopic data (1H-, 13C-NMR, IR, UV) for both tautomers are given. The X-Ray analysis of the acyclic compound 3a shows a central C=N bond with Z configuration and with s-gauche conformations of the adjacent C=O and C=N systems. According to quantum mechanical ab initio calculations (MP2/6-31G*/6-31G*) for the C3H4N2O model compounds, the ring tautomer 6 is by ca. 6 kcal/mol lower in energy than the acyclic forms 7. Within the series of open-chain tautomers 7, gauche forms are lower in energy than s-trans conformers, indicating that amide resonance is more important for these systems than polyene delocalization, s-cis Forms were found to be transition states. The acyclic conformers 7 are rather flexible; barriers of rotation for both C - N bonds are calculated to 4 - 5 kcal/mol only (RHF/ 3-21G/3-21G).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260417
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  • 10
    Electronic Resource
    Electronic Resource
    Alkoxy-substituted N-acyliminium salts  -  synthesis, structure, reactivityDedicated to Prof. Dr. Alan R. Katritzky FRS on the occasion of his 65th birthday. (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2069-2077 
    Details
    ISSN: 0009-2940
    Keywords: N-Acyliminium salts, alkoxy-substituted ; Iminium salts, N-acyl- ; Imides ; Alkylation ; Azavinylogous imides ; Amidines ; Calculations, ab initio ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkylation of aliphatic imides 5 by use of oxonium salts takes place at one of the carbonyl oxygen atoms, leading to alkoxy-substituted N-acyliminium salts 1. These new reactive intermediates are fully characterized by IR, 1H- and 13C-NMR spectroscopy and X-ray analysis. The stereochemical and dynamical properties of the model compounds 6, 7 are investigated by ab initio model calculations (MP2/6-31G*//6-31G*). The barrier of rotation around the central C - N bond in 6 is calculated to 10.2 kcal/mol. The reaction with CH acids 8 yields new types of enamides (9); primary amines 10 are converted to N-acylamidines 11. Primary amidines 12 react with 1 to form new 1,3-diazabutadiene derivatives 13. The reaction with primary amides 14 gives N,N-bisacylamidines 15. With primary N-acylamidines 16 new doubly azavinylogous imides 17 (1-oxa-3,5-diazahexatriene derivatives) are formed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260917
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