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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Organometallics 13 (1994), S. 4189-4193 
    ISSN: 1520-6041
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 81 (1998), S. 845-852 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Studies towards the synthesis of a chiral primary α-phosphinoalkanamine 1a are reported. O-Activated. N-carbamate-protected phenylalaninol 3a did not undergo SN reaction with KPPh2: instead, after N-deprotonation, intramolecular substitution led to formation of the aziridine derivative 5a (Scheme 2). N-Phthalimido-protected, O-activated phenylalaninol 3b also underwent an intramolecular process on treatment with KPPh2, i.e., an unusual aryl-acyliminium cyclization furnishing the (epoxymethano)isoindolo[1,2-a]isoquinolinone 7 (Scheme 3). In a reaction with KPPh2, the N,N-dibenzyl-protected and activated phenylalaninol 3d finally yielded the intermolecular SN reaction product 2a (Scheme 4). However, debenzylation by catalytic hydrogenation turned out to be impossible.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2511-2514 
    ISSN: 1434-193X
    Keywords: Biaryls ; Homogeneous catalysis ; Iron ; Michael additions ; Quinones ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dienol tautomers 2 of 2-acceptor-substituted cycloalkenones 1 undergo an iron(III)-catalyzed reaction sequence - formally a vinylogous Michael reaction - with benzoquinone derivatives 5 to yield products 6, 7 and 9, which are easily converted into highly functionalized biaryl compounds.
    Additional Material: 1 Tab.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1475-1479 
    ISSN: 1434-193X
    Keywords: Amino alcohols ; Asymmetric catalysis ; Chirality ; Michael additions ; Tridentate ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Novel C2-symmetric enantiopure β,β′-diamino thioethers 1 and β,β′-diimino thioethers 2 have been prepared from chiral α-amino acids. Nine of these compounds have been screened as ligands, in combination with 13 metal salts, with a view to achieving the enantioselective catalysis of a Michael reaction of a β-oxo ester with methyl vinyl ketone resulting in an optimal ee of 17%.
    Additional Material: 2 Tab.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 701-705 
    ISSN: 1434-193X
    Keywords: Asymmetric catalysis ; Catalysis ; Addition reactions ; N ligands ; Nickel ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Quaternary stereocenters were constructed with an enantioselectivity of up to 91% ee under aerobic conditions and at ambient temperature in the Michael reaction of β-dicarbonyl compounds and methyl vinyl ketone with Ni(OAc)2·4H2O and optically active trans-1,2-diaminocyclohexane as a chiral catalyst.
    Additional Material: 1 Tab.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 759-761 
    ISSN: 1434-193X
    Keywords: Catalysis ; Carbonyl compounds ; Iron compounds ; Michael reactions ; Tautomerism ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A double acceptor-activated cycloalkene 1 reacts in an FeCl3 · 6 H2O catalysed Michael reaction surprisingly as a donor. The constitution of the product 2 results from a reaction of 1 in the γ-position, thus the Michael reaction is vinylogous with respect to the donor. A tautomerism between the enone 1 and the dienol 4 is found to be a precondition for this reactivity.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1259-1266 
    ISSN: 1434-193X
    Keywords: Catalysis ; Carbonyl compounds ; Lanthanides ; Michael reaction ; Transition metals ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transition-metal catalysis of the Michael reaction of 1,3-dicarbonyl compounds with acceptor-activated alkenes is introduced as a valuable alternative to the classic base catalysis of this reaction. Owing to the mild, neutral reaction conditions, the chemoselectivity of these processes is superior to that offered by the base catalysis, since the latter suffers from various unwanted side- and subsequent reactions, such as aldol cyclizations and ester solvolyses. The most efficient transition-metal catalysts do not require inert or anhydrous conditions, even solvents are unnecessary in some cases, and quantitative conversions can be achieved at room temperature. Furthermore, the development of transition-metal catalysts on solid supports has allowed very simple work-up procedures. Despite the extraordinary chemoselectivity, in terms of diastereoselectivity transition-metal catalysis gives better results than base catalysis only in a very few special cases. Also, in terms of enantioselectivity, results recently achieved with basic rare-earth metal catalysts cannot be reproduced by transition metals. Nevertheless, with transition-metal catalysis, even new reactivities can be observed, which have hitherto been unknown for base-catalyzed systems. For example, Michael donor molecules have been found to react in an unprecedented vinylogous fashion.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1353-1358 
    ISSN: 0947-3440
    Keywords: Amino acid derivatives ; Chirality ; N ligands ; Protecting groups ; S ligands ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiral β-amino alcohols 2, available from natural α-amino acids by reduction, have been converted in a sequence of N-protection, O-activation, thioether formation, and deprotection to novel C2-symmetrical β,β′-diamino thioethers 1, which shall serve as chiral tridentate ligands in late transition metal complexes. Optical purity of compounds 1 was established by amide formation with (+)-O-acetylmandelic acid.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 157-161 
    ISSN: 0009-2940
    Keywords: Carbene ligands ; Chromium complexes ; Molybdenum complexes ; Tungsten complexes ; Annulation reaction ; Diels-Alder reaction ; Oxacyclopentenylidene ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of Complex Ligands, LXI[1]. - Oxacycloalkenylidene Complexes of Chromium, Molybdenum, and Tungsten: Synthesis, Their Annulation with Alkynes and Diels-Alder Reaction with DienesLithiiated propargylic ether 1 reacts with M(CO)6 (M = Cr, Mo, W) to give the 2-oxacyclic carbene complexes 2-4 containing an α,β-double bond and a cyclic acetal structure which serves as a protected benzoyl group. Reaction of the chromium complex 2 with tolan leads to an acyl hydroquinone derivative 5. The tungsten complex 3 undergoes a [4 + 2] cycloaddition with cyclopentadiene to give two diastereomeric oxatricyclic carbene complexes 6 and 7 with an endo/exo selectivity of 3:1. The stereochemistry of the Diels-Alder reaction is controlled by the configuration of the acetal carbon center.
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  • 10
    ISSN: 0009-2940
    Keywords: Vinylidene complexes ; Carbene complexes ; Molybdenum complexes ; (Alkynyl)carbene complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of [(η5-C5H5)(CO)2(NO)Mo] (1) with alkynyllithium and [(CH3)3O]BF4 affords the vinylidene-molybdenum complex 2 along with the methoxy(alkynyl)carbene molybdenum complex 3. Both compounds are characterized by an X-ray crystal structure analysis. Due to axial and central chirality in the LnM=C=CR2 moiety complex 2 is formed as a 2 : 1 mixture of two diastereomers. The formation of 2 and 3 can be understood in terms of a competitive attack of alkynyllithium at the carbonyl ligand and the molybdenum center.
    Additional Material: 2 Ill.
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