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  • 1
    Digitale Medien
    Digitale Medien
    Aromatic substitution. 56. Observation of aluminum trichloride-catalyzed trialkylsilylation of benzene and toluene with chlorotrialkylsilanes in the presence of Huenig bases (1989)
    s.l. : American Chemical Society
    The @journal of organic chemistry 54 (1989), S. 3770-3771 
    Details
    ISSN: 1520-6904
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/jo00277a005
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  • 2
    Digitale Medien
    Digitale Medien
    Catalytic enantioselective reactions driven by photoinduced electron transfer (2005)
    [s.l.] : Nature Publishing Group
    Nature 436 (2005), S. 1139-1140 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] Photoinduced electron transfer is an essential step in the conversion of solar energy into chemical energy in photosystems I and II (ref. 1), and is also frequently used by chemists to build complex molecules from simple precursors. During this process, light absorption generates ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/nature03955
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  • 3
    Digitale Medien
    Digitale Medien
    A new heterocylic ring system in (4SR,6SR)-6-(2-phenylethyl)-4-phenyl-1,4,3-oxathiazin-2(6H)-one (2001)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. o252-o253 
    Details
    ISSN: 1600-5368
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Notizen: The title compound, C17H17NO2S, is formed by reaction of 2-azidocarbonyloxy-4-phenyl-1-thiophenylbutane with iron(II) chloride as catalyst. This is the first example of the 1,4,3-oxathiazin-2(6H)-one ring system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S160053680100304X
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  • 4
    Digitale Medien
    Digitale Medien
    (±)-(1RS,2SR)-1,2-Bis(2′-methyl-3′-oxocyclohex-1′-enyl)-1,2-diphenylethane (2001)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. o1145-o1146 
    Details
    ISSN: 1600-5368
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Notizen: The title compound, C28H30O2, was obtained by an unprecedented osmium tetraoxide-mediated dimerization of (2′-methyl-3′-oxocyclohex-1′-enyl)phenylethane. The trans stereochemistry was revealed by X-ray crystallography. The molecule exhibits a crystallographic center of inversion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S1600536801018384
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  • 5
    Digitale Medien
    Digitale Medien
    Diastereomerically Pure 3-(Silyloxy)oxetanes by a Selective Paternò-Büchi Reaction (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2457-2466 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Paternò-Büchi reaction ; Oxetanes ; Diastereoselectivity ; Enol silyl ethers ; Photocycloaddition ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Diastereomerically pure 3-[(trimethylsilyl)oxy]oxetanes 3 were prepared in moderate to good yields (45-72%) by the Paternò-Büchi reaction of silyl enol ethers 2 with benzaldehyde. The photocycloaddition exhibits a high degree of regio- and diastereoselectivity. The substituents R in the silyl enol ether have been varied [R = Me, Et, iPr, tBu, Ph, CH(OMe)2, CH(OCH2)2, C(OCH2)2Me], and it was found that steric bulk is mainly responsible for enhanced selectivity (diastereoselectivity from 70:30 up to 95:5). The regiochemical control is perfect (regioselectivity 〉95:5) except for silyl enol ether 2a (R = Me) in the case of which a 90:10 ratio of regioisomers was observed. Irradiation of the reaction mixture at lower temperature (-25°C) led to a further improvement of diastereoselectivity. The relative configuration of the products obtained was elucidated both by 1H-NMR spectroscopy and by chemical degradation. As a mechanistic hypothesis to explain the high observed diastereoselectivity we propose that the steric environment in the intermediate diradical 11 determines the selectivity according to two possible reaction pathways, i.e. bond formation and retrocleavage.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19931261120
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  • 6
    Digitale Medien
    Digitale Medien
    Diastereomerically Pure 1,2-Diols by Nucleophilic Displacement Reactions of 3-Oxetanols - A Study Directed Towards the Identification of Suitable Nucleophiles and the Elucidation of Possible Side Reactions (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2161-2169 
    Details
    ISSN: 1434-193X
    Schlagwort(e): Photocycloaddition ; Ring opening ; Oxetanes ; 1,2-Diols ; Alkyldealkoxylation ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The ring opening of 3-isopropyl-2-phenyl-3-oxetanol (2a) by various nucleophiles has been studied. In the presence of BF3 as a Lewis acid, a clean reaction at the less substituted C-4 position was observed and the corresponding 1,2-diols 6-11 and 21-23 were isolated in diastereomerically pure form (47-97% yield). Alkyl-, aryl-, alkynyl- and alkenyllithium compounds proved to be suitable carbon nucleophiles. Deprotonated thiols were used as sulfur nucleophiles. An alkoxide derived from benzyl alcohol and an amide derived from benzylamine reacted less readily under these conditions, yielding the 1,2,3-trifunctional compounds 24 (42% yield) and 26 (54% yield). Other 2-phenyl-3-oxetanols such as 2b and 2c can also be employed as electrophiles, whereas 2-anisyl derivatives preferentially undergo rearrangement reactions, as exemplified by the conversion of oxetane 16 to the hydroxy ketone 17 (84% yield). The superior behaviour of 3-oxetanols as compared to their silyl derivatives in reactions with nucleophiles became evident from the reaction of 3-silyloxyoxetane 1a with alkyllithium reagents. A β elimination occurred upon treatment with nBuLi, which, after pericyclic ring opening and addition of nBuLi, yielded the allylic alcohol 20.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    The Preparation of 2,3,5-Tri- and 2,3-Disubstituted Furans by Regioselective Palladium(0)-Catalyzed Coupling Reactions: Application to the Syntheses of Rosefuran and the F5 Furan Fatty Acid (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2045-2057 
    Details
    ISSN: 1434-193X
    Schlagwort(e): Homogenous catalysis ; Palladium ; Cross-coupling ; Heterocycles ; Synthetic methods ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The 5-acceptor-substituted 2,3-dibromofurans 1 and 2 underwent a regioselective Pd0-catalyzed coupling reaction at the C-2 carbon atom. With alkynes the corresponding 2-alkynylfurans 4 and 5 were accessible (49-97% yield). Alkyl-, aryl-, and alkenylzinc reagents gave the 2-substituted furans 8 starting from compound 2 (66-84% yield). The 2-allylfurans 8e and 8f were obtained by a regioselective Stille coupling in 79% and 73% yield. The latter reaction was also applied to the parent 2,3-dibromofuran (27) and yielded the substitution product 28 (60% yield). Subsequent Pd0-catalyzed reactions to introduce a methyl group in 3-position by a methyldebromination were successfully conducted for 2-alkynyl-3-bromofurans with MeZnCl and PdCl2(PPh3)2 as the catalyst in THF (reflux) to yield compounds 13-16 and 24 (67-76%) and with SnMe4 and PdCl2[P(o-Tol)3]2 as the catalyst in DMA (90 °C) for the 2-allyl-3-bromofuran 8e to yield 18 (70%). The more facile reaction of the 2-alkynylfurans relative to those of furans bearing an sp3-carbon atom at C-2 appears to be due to steric reasons. Studies on the 2-alkyl-3-bromofuran 20 supported this notion. With the regioselective coupling methodology the terpene rosefuran (22) was prepared in four steps starting from furan 2 (35% yield overall). The F5 furan fatty acid (26) was synthesized from furan 1 in five steps (29% yield overall).
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Diastereomerically Pure 3-Alkoxy- and 3-Acyloxyoxetanes from 3-silyloxyoxetanes. A case study (1996)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 338 (1996), S. 750-753 
    Details
    ISSN: 0941-1216
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prac.199633801146
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  • 9
    Digitale Medien
    Digitale Medien
    Regioselective ring opening of oxetanes by hydrogenolysis. - A convenient method for the carbohydroxylation of enol ethers (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1045-1053 
    Details
    ISSN: 0947-3440
    Schlagwort(e): Photocycloaddition ; Hydrogenolysis ; Oxetanes ; Carbohydroxylation ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Hydrogenolysis of the 2-aryl-3-(silyloxy)oxetanes 1, 2, 5, and 9 in the presence of Pd(0) catalysts (Pd/C) yields 1,2-diols as ring-opened products almost quantitatively (82-98% yield). In combination with the preceding photocycloaddition it facilitates the regio- and stereoselective carbohydroxylation of silyl enol ethers (total yield: 43-74%). In the case of β-substituted silyl enol ethers (R1 = alkyl) the reaction sequence leads to a single diastereomeric product (4, 6, 10) in a simple two-step procedure. Acid-sensitive substrates such as the dioxolane 1g or the dihydrofuran-derived oxetane 11 are mildly cleaved in the presence of Pd(OH)2. As demonstrated by selected examples (13, 16, 18) the produced 1,2-diol remains silyl-protected if Pd(OH)2 is employed as a catalyst for the hydrogenolysis. In the latter case the silyl protective group stays at the tertiary hydroxy group to which it has been attached in the oxetane, but silyl migration may intervene as was found in the case of the sterically congested oxetane 18.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jlac.1995199506148
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  • 10
    Digitale Medien
    Digitale Medien
    A Short Synthesis of (±)-Oxetin (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2265-2267 
    Details
    ISSN: 0947-3440
    Schlagwort(e): Antibiotics ; Amino acids ; Photochemistry ; Oxetanes ; Protective groups ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The antibiotic β-amino acid oxetin (rac-1) has been prepared by the stereoselective Paternò-Büchi reaction of enecarbamate 2 and n-butyl glyoxylate (5). The overall yield of the four-step synthesis is 14%. The order of the deprotection steps proved to be important in minimizing possible side reactions.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jlac.199719971113
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