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  • 1
    Electronic Resource
    Electronic Resource
    Enantioselectivity of the Transfer of Hydrogen Atoms to Acyclic Prochiral Carbon-Centred Radicals Using Chiral Tin Hydrides (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 177-181 
    Details
    ISSN: 1434-193X
    Keywords: Radicals ; Chiral tin hydrides ; Enantioselective radical reactions ; Reductions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Racemic α-bromo esters 2 have been reduced via prochiral radicals 5 with low to moderate enantioselectivities using chiral tin hydrides 1 with a stereogenic tin atom containing chiral 2-[(1-dimethylaminoalkyl)phenyl] ligands. The tin hydrides 1 were mixtures of diastereomers. It could be shown that the minor diastereomer of tin hydrides 1a and 1b reacts with good enantioselectivity whereas the major diastereomer reacts almost unselectively. The observed enantioselectivities are also strongly influenced by steric effects of the substituents attached to the radical centre.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New Type of Skipped Oligoaziridines: Synthesis of New Fatty AcidDerivatives Containing Aziridine Functions (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 661-664 
    Details
    ISSN: 1434-193X
    Keywords: Aziridines ; N-Heterocycles ; Fatty acids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The first successful preparation of the aziridines methyl cis-9,10;cis-12,13-diepiminooctadecanoate (3) derived from linoleic acid, and methyl cis-9,10;cis-12,13;cis-15,16-triepiminooctadecanoate (6) derived from linolenic acid, is reported. Remarkably, the bis- and trisaziridine were obtained in a reaction sequence that consists of only two steps, using technically pure methyl esters of epoxidized sunflower and linseed oil. The conversion of methyl 9,10;12,13-diepoxyoctadecanoate (1), with sodium azide and ammonium chloride in ethanol in the presence of water, yielded the new diazidodihydroxy compound methyl 9(10),12(13)-diazido-10(9),13(12)-dihydroxyoctadecanoate (2) in the first step. 2 was obtained as a regioisomeric mixture. The reaction of 2 with triphenylphosphane led to the bisaziridine 3. The analogous conversion of methyl 9,10;12,13;15,16-triepoxyoctadecanoate (4), via the new triazidotrihydroxy compound methyl 9(10),12(13),15(16)-triazido-10(9),13(12),16(15)-trihydroxyoctadecanoate (5), afforded trisaziridine 6.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Thermisch initiierte Addition von Alkanen an Alkene. V. Addition von Cyclohexan an Oct-1-en in einer freien Radikalkettenreaktion unter überkritischen BedingungenHerrn Prof. Dr. habil. G. Zimmermann zum 60. Geburtstag gewidmet (1990)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 332 (1990), S. 767-781 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermal Addition of Alkanes to Alkenes. V. Addition of Cyclohexane to 1-Octene in a Free Radical Chain Reaction at Supercritical Fluid ConditionsAlkanes can be added to alkenes in a thermally initiated free radical chain reaction (“ane reaction”). Kinetic and mechanistic studies on the addition of cyclohexane (1) to 1-octene (2) (molar ratio = 100:1) at 330-450°C and pressures of up to 300 bar have been performed in a high pressure - high temperature flow apparatus (“HP-HT” apparatus). The free radical chain is initiated by comproportionation of 1 and 2 to give alkyl radicals 6 and 7. Addition of cyclohexyl radical 6 to alkene 2 and competing abstraction of an allylic hydrogen atom from 2 give radicals 7a and 8, respectively. Subsequent stabilization of the radicals 7a and 8 by hydrogen abstraction from 1 yields the addition product cyclohexyloctane (3) and isomerized octenes (4), respectively. The relative rate of addition and isomerization can be controlled by pressure and temperature. The regioselectivity of the addition reaction was also measured.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19903320528
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  • 4
    Electronic Resource
    Electronic Resource
    Hochdruck-hochtemperatur-reaktionen in einem strömungsreaktor, 1211. Mitteilung: cf.1. Thermische dimerisierung von acrylsäauremethylester, methylvinylketon und acrylnitril (1983)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 184 (1983), S. 63-69 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermal dimerization of methyl acrylate to dimethyl 2-methyleneglutarate was performed in a high pressure-high temperature flow apparatus at temperatures up to 420°C and pressures up to 200 bar. The head to head dimer dimethyl 2-methyl-3-methylenesuccinate was observed, too. Methyl vinyl ketone and acrylonitrile are able to dimerize analogously.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1983.021840107
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  • 5
    Electronic Resource
    Electronic Resource
    Ethylaluminium Dichloride Induced Reactions of Acetals with Unsaturated Carboxylic Esters: Synthesis of Homoallyl Ethers (1996)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1996 (1996), S. 1851-1854 
    Details
    ISSN: 0947-3440
    Keywords: Homoallyl ethers ; Acetals ; Unsaturated fatty esters ; Addition reactions ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ethylaluminium dichloride induced reactions of methyl 10-undecenoate (1) with dimethyl acetals of formaldehyde 2a, acetaldehyde 2b, isobutyraldehyde 2c, and pivaldehyde 2d gave the corresponding homoallyl ethers 3a, 3b, 3c, and 3d in yields of 48-70%. The products were obtained as mixtures of the (E) and (Z) stereoisomers. With formaldehyde dimethyl acetal (2a), methyl oleate (6), and methyl petroselinate (11) gave the corresponding regioisomeric (E)-configured homoallyl ethers 7/8 and 12/13.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199619961119
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  • 6
    Electronic Resource
    Electronic Resource
    Radical Additions of Alkyl 2-Haloalkanoates and 2-Haloalkanenitriles to Alkenes Initiated by Electron Transfer from Copper in Solvent-Free Systems (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2303-2313 
    Details
    ISSN: 0947-3440
    Keywords: Electron transfer reactions ; Radical additions ; 1,3-Asymmetric induction ; Alkenes ; γ-Lactones ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkyl 2-iodoalkanoates 2, and 2-iodoalkanenitriles 15 were added, with copper powder, to the 1-alkenes 1a, e, f, and h, and to the alkenes 1b, c, d, and g with a 1,2-dialkyl substituted double bond, to give, respectively, γ-lactones and 4-iodoalkanenitriles in very good yields. No solvent was used. The reaction is a free radical addition initiated by electron transfer from copper to the activated iodoalkane. Yields were lower using the respective bromo compounds. In situ formation of the iodo compounds, by addition of stoichiometric amounts of sodium iodide to the reaction mixture, gave improved yields. In the case of the methyl bromomalonates 6, the addition of sodium iodide proved to be unnecessary. The diastereoselectivity of the addition reaction by relative 1,3-asymmetric induction was rationalized by consideration of the steric interactions of the substituents in the transition state which is formed in the process of iodine transfer to the chiral adduct radical.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971119
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  • 7
    Electronic Resource
    Electronic Resource
    Stereoselectivity of the Thermally Initiated Free-Radical Chain Addition of Cyclohexane to 1-Alkynes (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2493-2499 
    Details
    ISSN: 0009-2940
    Keywords: Radicals ; Addition ; Stereoselectivity ; Alkynes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkanes can be added to alkynes in a thermally initiated free-radical chain reaction (“ane reaction”). The addition of cyclohexane to 1-alkynes 1a-1 yields a mixture of (Z)- and (E)-2-cyclohexyl-1-alkenes 3a-1. An essential step in this reaction is the addition of cyclohexyl radicals to the alkynes to give 2-cyclohexyl-1-alkenyl radicals 2a-1 which abstract hydrogen from cyclohexane to yield the products 3a-1. The stereoselectivity of the addition has been measured in the temperature range of 160-260°C. It strongly depends on the substituent X of the radical center and varies over a range of almost four orders of magnitude from [(Z)-3a]:[(E)-3a] = 33 (X = OMe) at 160°C to [(Z)-31]:[(E)-31] = 0.012 (X = tBu) at 260°C. The stereoselectivity is further influenced by the temperature and in most cases by the concentration of the hydrogen donor cyclohexane. The reaction is discussed in terms of the stereoselectivity of the addition of cyclohexyl radicals to the alkyne, of the structure of the 1-alkenyl radical (σ and π radical, respectively), the rate of inversion in the case of σ alkenyl radicals, and the relative rates of syn and anti hydrogen transfer.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261124
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  • 8
    Electronic Resource
    Electronic Resource
    Thermally Initiated Free-Radical Chain Addition of Alkanes to Alkynes, II. Kinetics of the Addition of Cyclohexane to Phenylethyne under Supercritical Fluid Conditions (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 673-675 
    Details
    ISSN: 0009-2940
    Keywords: Radicals ; Addition ; Alkynes ; Kinetics ; Supercritical fluid conditions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the addition of cyclohexane (2) to phenylethyne (1) proceeding via 2-cyclohexyl-1-phenylethenyl radical (3) to give 1-cyclohexyl-2-phenylethene (4) was investigated in the temperature range from 260 to 340°C. The radical chain is initiated by a bimolecular reaction of cyclohexane with phenylethyne to give a cyclohexyl radical and a 1-phenylethenyl radical. The physical state of the reaction mixture was varied from liquid to supercritical and to gasphase conditions. No effect on the reaction rate constant near the critical point was observed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270416
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis of Novel Optically Active Tin Hydrides Containing Chiral Ligands (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1539-1546 
    Details
    ISSN: 0009-2940
    Keywords: Chiral tin hydrides ; Chiral hydrogen donors ; Tin ; Ligand effects ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the chiral tin bromides 1-4 and hydrides 5-8, containing the potentially bidentate, optically active 2-[ (1 S/R)- 1 -dimethylaminoethyl]phenyl and 2 -[( 1 S) - 1 -dimethylamino-2,2-dimethylpropyl]phenyl ligands, is reported. The tin hydrides 5-8, with the tin atom as the stereogenic centre, were isolated as diastereomeric mixtures with diastereomeric ratios of dr = 50:50 up to dr = 80:20. The absolute configuration of ( - ) - (1 S)- 1 - (2-bromophenyl) -2,2-dimethylpropylamine [(S)-10] was determined by single-crystal X-ray structure analysis.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301030
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  • 10
    Electronic Resource
    Electronic Resource
    Stereoselectivity of the Transfer of Hydrogen Atoms to Cyclic Alkyl Radicals (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1069-1073 
    Details
    ISSN: 0009-2940
    Keywords: Free-radical additions ; Alkyl radicals ; Stereoselectivity ; Hydrogen transfer ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The addition of cyclohexane to alkylmaleic anhydrides 1a-f via cyclic radicals 2a-f gave a mixture of (Z)- and (E)-2,3-dialkylsuccinic anhydrides 3a-f. The stereoselectivity of the hydrogen transfer from cyclohexane to radicals 2a-d was measured in the temperature range of 200-260°C, and the relative activation parameters of the formation of (Z)- and (E)-3 were determined. The stereoselectivity of the hydrogen transfer from cyclohexylmercuric hydride at 25°C was measured as well. The results are rationalized assuming steric interactions in the transition state of H donor and β substituent and of α and β substituent, respectively. An X-ray structure analysis of the highly strained addition product (Z)-3d was performed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270616
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