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  • 1
    Electronic Resource
    Electronic Resource
    Enantionselektive Synthese des L-Threonins (1987)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 232-236 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An Enantionselective Synthesis of L-ThreonineAn enantioselective synthesis of L-threonine (1) is described. Racemic ethyl 2-acetamido-3-oxobutyrate (6) was synthesized from ethyl acetoacetate (2) [4][5] and then transformed to the epimeric optically active alcohols 7a and 7b by microbiological reduction with Saccharomyces rouxii. The Mixture 7a/7b could be converted to 1 by slightly modified, known Methods in a yield of ca. 52% with respect to 7a/7b.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19870700128
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  • 2
    Electronic Resource
    Electronic Resource
    Nuhn, P.; Hofmann, H.- J.: Molekulare Wirkungsmechanismen von Pharmaka. Eine Einfuhrung in die Molekularpharmakologie. - E. Hofmann, 188 S., 30 Abb., 17 Tab., Berlin: Akademie-Verlag 1985. Wissenschaftliche Taschenbücher (WTB/Biologie) Brosch. 16, - M (1985)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 327 (1985), S. 1036-1036 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19853270626
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  • 3
    Electronic Resource
    Electronic Resource
    Tetrazolverbindungen. 1. 1-Aryl-5-(2-dialkylamino-vinyl)-1H-tetrazole aus 3-Chlor-propen-iminiumsalzen (1988)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 330 (1988), S. 963-973 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrazole Compounds. 1. 1-Aryl-5-(2-dialkylamino-vinyl)-1H-tetrazoles from 3-Chloropropeniminium Salts3-Chloropropeniminium salts 1 react with excess sodium azide in refluxing alcohols to give mainly 1-aryl-5-(2-dialkylamino-vinyl)-1H-tetrazoles 3; in minor quantities isomeric 5-aryl-1-(2-dialkylamino-vinyl)-1H-tetrazoles 4 are formed. The reaction involves splitting off N2 and C → N migration of the aryl and dialkylaminovinyl group, respectively. A cross-over experiment indicated that the rearrangement step proceeds intramolecularly.  -  The i.r., u.v., and n.m.r. spectroscopic data of the novel 1H-tetrazoles 3 as well as the u.v. spectra of some new starting products 1k - v are reported.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19883300617
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  • 4
    Electronic Resource
    Electronic Resource
    Tetrazolverbindungen. 3. Modifizierung von (1-Aryl-1H-tetrazol-5-yl)-acetaldehyd-Enaminen durch säurekatalysierte Umaminierung (1988)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 330 (1988), S. 981-992 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrazole Compounds. 3. Modification of 1-Aryl-1H-tetrazole-5-acetaldehyde Enamines by Acid-Catalyzed TransaminationThe acid-catalyzed transamination of tetrazole-5-acetaldehyde enamines proves to be a useful synthetic method for preparing specially N-substituted enamines of this series not accessible directly from 3-chloro-propeniminium salts 3 and sodium azide. Thus, starting from (E)-1-aryl-5-(2-dimethylamino-vinyl)-1H-tetrazoles 5 transamination with dialkylamines yields tertiary enamines of types 6 and 7. Analogously, acid-catalyzed reaction of 5 with N-alkylanilines leads to 1-aryl-5-[2-(N-alkylanilino)-vinyl]-1H-tetrazoles 8. Bifunctinal secondary amines such as N,N′-dimethylethylenediamine result in systems of type 9 with two linked tertiary tetrazolyvinylamino groups. All the transaminations with secondary amines proceed with retention of configuration. According to the same reaction scheme transamination of 5 (Ar = Ph) with primary alkyl-, aralkyl-, and arylamines affords secondary tetrazolylvinylamines 10; however, here the formation of Z-configurated products dominates. Bifunctional primary amines like ethylenediamine and 1,2-phenylenediamine react with 5 to give the N,N′-linked systems 11 and 12 possessing two secondary tetrazolylvinylamino groups. - Characteristic i.r., u.v., and 1H-n.m.r. spectroscopic data of the novel tetrazole-5-acetaldehyde enamines are reported.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19883300619
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  • 5
    Electronic Resource
    Electronic Resource
    Pyryliumverbindungen. 41. 7aH-Cyclopenta[b]pyran-7-one durch Ringtransformation von 2,4,6-Triaryl-pyryliumsalzen mit acyclischen 1,2-Diketonen (1989)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 331 (1989), S. 293-305 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pyrylium Compounds. 41. 7aH-Cyclopenta[b]pyran-7-ones by Ring Transformation of 2,4,6-Triarylpyrylium Salts with Acyclic 1,2-DiketonesReaction of 2,4,6-triarylpyrylium salts 1 with acyclic 1,2-diketones 2 (CH3COCOR, R = Me, Ph) in the presence of an appropriate condensing agent (e.g. piperidine acetate, triethyl-amine/acetic acid, sodium acetate) yields the hitherto unknown 2,4,5,7a-substituted 7aH-cyclopenta[b]pyran-7-ones 3 as a result of a new type of ring transformation (2,5-[C4O+C]/2,3-[C2+C3]). A characteristic feature of compounds 3 is their ability to undergo electrophilic substitutions. Thus, stepwise bromination of the 7a-methyl derivative 3a in acetic acid affords 6-bromo-7a-methyl-2,4,5-triphenyl-cyclopenta[b]pyran-7-one (4) and 3,6-dibromo-7a-methyl-2,4,5-triphenyl-cyclopenta[b]pyran-7-one (5); analogously, nitration of 3a leads to 7a-methyl-6-nitro-2,4,5-triphenyl-cyclopenta[b]pyran-7-one (6), indicating that position 6 is the favoured position for electrophilic substitutions. Contrary to the 3,5-unsubstituted pyrylium salts 1, the 3,5-dimethyl-2,4,6-triphenyl-pyrylium perchlorate (13) reacts with 1,2-diketones 2 through a 2,6-[C5+C] transformation to give arylsubstituted 1,2-diones 14. The structure of the new compounds was determined by spectroscopic methods and by a single crystal X-ray analysis of the dibromo derivative 5.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19893310216
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  • 6
    Electronic Resource
    Electronic Resource
    Pyryliumverbindungen. 44 [1]. 2-(2-Hydroxy-3-oxo-cycloalk-1-enyl)-2H-thiopyrane aus 2,4,6-Triaryl-thiopyryliumsalzen und Cycloalkan-1,2-dionen (1989)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 331 (1989), S. 853-858 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pyrylium Compounds. 44. 2-(2-Hydroxy-3-oxo-cycloalk-1-enyl)-2H-thiopyranes from 2,4,6-Triarylthiopyrylium Salts and Cycloalkane-1,2-diones2,4,6-Triarylthiopyrylium salts 5 react with cyclopentane-1,2-dione (2a) or cyclo-hexane-1,2-dione (2b) in the presence of an appropriate acid binding agent (e.g. sodium acetate, piperidine acetate, triethylamine/acetic acid, triethylamine) to give the hitherto unknown 2-(2-hydroxy-3-oxo-cycloalk-1-enyl)-2H-thiopyranes 6. - The structure of the novel compounds was established by n.m.r., i.r. and u.v. spectroscopic methods.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19893310520
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  • 7
    Electronic Resource
    Electronic Resource
    Pyryliumverbindungen. 42. Benzocycloalkenone und Dihydro-2H,7H-1-benzopyranone aus 2,4,6-Triaryl-pyryliumsalzen und Cycloalkan-1,2-dionen (1989)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 331 (1989), S. 306-318 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pyrylium Compounds. 42. Benzocycloalkenones and Dihydro-2H,7H-1-benzopyranones from 2,4,6-Triarylpyrylium Salts and Cycloalkane-1,2-diones2,4,6-Triarylpyrylium salts 1 react with cycloalkane-1,2-diones 2 in the presence of an appropriate condensing agent to yield benzocycloalkenones 3. Thus, sodium acetate and cyclo-hexane-1,2-dione (2a) lead to the dihydro-2H-naphthalenones 3a-i, whereas with cycloheptane-1,2-dione (2b) and piperidine acetate, triethylamine or sodium acetate the tetrahydro-5H-benzo-cyclohepten-5-ones 3j-r are formed. As shown for the example 3a, j → 4a, b, benzocycloalkenones of type 3 can be converted into phthalazines 4 on heating with hydrazine in ethanol. By reaction of the dione 2a and an equimolar mixture of triethylamine and acetic acid or morpholine acetate with the salts 1 5,6-dihydro-2H,7H-1-benzopyran-8-ones 5 are obtained as a result of a new type of ring transformation. The pyrans 5 can be cleaved with perchloric acid in ethanol to 5,6,7,8-tetrahydro-8-oxo-1-benzopyrylium perchlorates 6. If the pyrans 5 are heated with sodium acetate in ethanol, a conversion to benzocycloalkenones 3 is achieved (cf. 5a → 3a). The structure of the new compounds was established by spectroscopic methods.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19893310217
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  • 8
    Electronic Resource
    Electronic Resource
    Pyryliumverbindungen. 43 [1]. Arylsubstituierte 5-(2-Dialkylamino-thiazol-5-yl)-pentadienone aus 2,4,6-Triaryl-pyryliumsalzen und 2-Dialkylamino-4-arylthiazolen (1989)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 331 (1989), S. 843-852 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pyrylium Compounds. 43. Arylsubstituted 5-(2-Dialkylamino-thiazol-5-yl)-pentadienones from 2,4,6-Triarylpyrylium Salts and 2-Dialkylamino-4-aryl-thiazoles2,4,6-Triarylpyrylium salts 1 react with 2-dialkylamino-4-aryl-thiazoles 7 (used in substance or prepared in situ from α-thiocyanato-acetophenones 9) in the presence of an appropriate acid-binding agent (e.g. piperidine acetate or sodium acetate) to give 5-(2-dialkylamino-4-aryl-thiazol-5-yl)-1,3,5-triaryl-penta-2,4-dien-1-ones 8. As reaction medium aliphatic alcohols (ethanol, n-propanol), dipolar aprotic solvents (acetonitrile) or chlorinated hydrocarbons (methylene chloride, chloroform) can be used. On the other hand, under the same conditions 2-amino-4-phenyl-thiazole (10) reacts with salts of type 1 via pyrylium ring transformation yielding 2,4,6-triaryl-1-(4-phenyl-thiazol-2-yl)-pyridinium perchlorates 11.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19893310519
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  • 9
    Electronic Resource
    Electronic Resource
    Tetrazolverbindungen. 2. (1-Aryl-1H-tetrazol-5-yl)-acetaldehyd-Derivate aus 1-Aryl-5-(2-dimethylamino-vinyl)-1H-tetrazolen (1988)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 330 (1988), S. 974-980 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrazole Compounds. 2. 1-Aryl-1H-tetrazole-5-acetaldehyde Derivatives from 1-Aryl-5-(2-dimethylamino-vinyl)-1H-tetrazoles1-Aryl-5-(2-dialkylamino-vinyl)-1H-tetrazoles 2, easily accessible by the reaction of 3-chloro-propeniminium salts 1 with excess sodium azide in refluxing alcohols, represent enamines of the hitherto unknown 1-aryl-1H-tetrazole-5-acetaldehydes 3. Attempts to isolate the latter after acid-catalyzed hydrolysis of 2 were unsuccessful. However, generated in situ, they can be trapped by suitable aldehyde reagents. Thus, starting from 1-aryl-5-(2-dimethylamino-vinyl)-1H-tetrazoles 4, the 4-nitrophenylhydrazones 5a--hyphen;i, 2,4-dinitrophenylhydrazones 5j--hyphen;r, and thiosemicarbazones 6 of the corresponding 1-aryl-1H-tetrazole-5-acetaldehydes 3 were obtained. Analogously, acid-catalyzed hydrolysis of 4 in the presence of 1,2-dianilinoethane resulted in 1-aryl-5-(1,3-diphenyl-2-imidazolidinylmethyl)-1H-tetrazoles 7. --hyphen; The structure of the aldehyde derivatives 5, 6, and 7 was proved by 1H n.m.r. spectroscopy.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19883300618
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  • 10
    Electronic Resource
    Electronic Resource
    Vinyloge Acylverbindungen. XXI. 1H-NMR-spektroskopische Untersuchungen an 3-Chlor-propen-iminiumsalzen (1989)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 331 (1989), S. 111-114 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Vinylogous Acyl Compounds. XXI. 1H-N.M.R. Spectroscopic Investigations on 3-Chloropropen-iminium SaltsThe 1H-n.m.r. data of a series of 3-aryl-3-chloropropeniminium salts 5 are reported. From the vicinal coupling constants 3J(H1, 2H) as well as from NOE difference spectra follows that salts of type 5 have throughout E(1,2)Z(2,3) configuration.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19893310117
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