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  • Wiley-Blackwell  (92)
  • Cell Press  (4)
  • 1995-1999  (91)
  • 1970-1974  (5)
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  • 1
    Electronic Resource
    Electronic Resource
    Regiospecific Hydroxylation of Metallodisilanes of the Iron Group - An Impressive Example of the Transition Metal Effect (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1585-1587 
    Details
    ISSN: 1434-1948
    Keywords: Metallodisilanes ; Oxofunctionalization ; Metallodisilandiols ; Silanetriols ; Metallosiloxanes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of the ferriodisilanes C5R5(OC)2Fe-Si2H5 [R = H (1a), Me (1b)] with dimethyldioxirane leads to selective insertion of oxygen into the α-Si-H bonds to yield the ferriodihydroxydisilanes C5R5(OC)2Fe-Si(OH)2-SiH3[R = H (2a), Me (2b)]. Another access to yield 2a is opened by hydrolysis of the dichloro(ferrio)disilane Cp(OC)2Fe-SiCl2-SiH3 (3a). Treatment of the pentachloro(metallo)disilanes C5H5(OC)2Fe-Si2Cl5 (4a) and C5Me5(OC)2Ru-Si2Cl5 (4b) with water results in regiospecific hydroxylation of the β-silicon atom to generate metallodisilanetriols C5R5(OC)2M-SiCl2-Si(OH)3 [M = Fe, R = H (5a); M = Ru, R = Me (5b)]. Controlled condensation of 5b with Me2Si(H)Cl leads to the novel rutheniosiloxane C5Me5(OC)2Ru-SiCl2-Si(OSiMe2H)3 (6).
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Poly[(S)-(+)-2-methylbutyl]pentylsiloxane (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 169-177 
    Details
    ISSN: 0887-624X
    Keywords: polysiloxane ; hexagonal columnar mesophase ; optically active polymers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly[(S)-(+)-2-methylbutyl]pentylsiloxane has been synthesized by anionic ring opening polymerization of the corresponding strained cyclic trisiloxane \documentclass{article}\pagestyle{empty}\begin{document}$ (D^{\rm{MeBu, Pe}}_{3}) $\end{document} with cryptated lithium (Li+/[211]) as counterion. The polymer did not show the low and high temperature crystalline phases, that are generally found for poly(di-n-alkylsiloxane)s. Instead, the material formed a hexagonal columnar mesophase until it melted around 400°C. MAS and solution 13C- and 29Si-NMR, polarizing microscopy and WAXS indicated an unexpectedly regular chain structure. It was tentatively concluded that the steric interaction of the (S)-(+)-2-methylbutyl side chains introduces sufficient regularity of the tacticity and that the chains tend to adopt a defect helix conformation. On the other hand, DSC showed the presence of a glass transition at -113°C, indicating a high flexibility of the backbone. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 169-177, 1998
    Additional Material: 7 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Configurational assignment of optically active hydroperoxy homoallylic alcohols and the corresponding diols by circular dichroism and multidimensional gas chromatography (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 69-74 
    Details
    ISSN: 0899-0042
    Keywords: diols ; hydroperoxides ; absolute configuration ; exciton coupling ; circular dichroism ; enantiomeric separation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Allylic hydroperoxides are a class of compounds of versatile synthetic utility. Optically active diastereomeric hydroperoxy homoallylic alcohols and their corresponding diols are easily available through horseradish peroxidase (HRP)-catalyzed kinetic resolution of racemic hydroperoxides. Here we describe the assignment of the absolute configuration of the optically active products and substrates obtained after HRP-catalysis by the circular dichroism exciton chirality method. Moreover, the analytical-scale separation of the enantiomers based on multidimensional gas chromatography on chiral columns is presented. Since the enantiomeric elution order on the ciral columns was constituted, the absolute stereochemistry of optically active allylic diols can easily be deduced by their retention times on β-cyclodextrins. Chirality 9:69-74, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    A new class of network-polymeric chiral stationary phases (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 248-256 
    Details
    ISSN: 0899-0042
    Keywords: chiral discrimination ; chiral stationary phase ; network polymer ; DATD ; hydrogen bonding ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A strategy based on the use of homo bi- and multifunctional building blocks for the synthesis of a new class of network-polymeric chiral stationary phases has been evaluated. The key steps comprise acylation of N,N′-diallyl-L-tartardiamide (DATD) and reaction with a multifunctional hydrosilane, yielding a network polymer incorporating the bifunctional C2-symmetric chiral selector. Covalent bonding to a functionalized silica takes place during the latter process. Many of these chiral sorbents show interesting enantioselective properties toward a wide variety of racemic solutes under normal-phase (hexane-based) conditions. The retention is mainly caused by the hydrogen-bonding ability of the analyte, which is regulated by mobile phase additives like alcohol or ether cosolvents. The most interesting chiral stationary phases, in terms of broad enantioselectivity, were obtained from O,O′-diaryol-DATD-derivatives, particularly those containing the 3,5-dimethylbenzoyl and the 4-(tert-butyl)benzoyl moieties. Since high column efficiencies can be obtained with these chiral sorbents, an α-value of ca. 1.2 is usually sufficient to produce baseline separation. A large number of neutral as well as acidic or basic drug racemates are resolved without derivatization. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070411
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  • 5
    Electronic Resource
    Electronic Resource
    Molecularly thin films of metallodendrimers (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 540-545 
    Details
    ISSN: 0894-3230
    Keywords: metallodendrimers ; molecularly thin films ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A non-covalent synthesis route to assemble metallodendrimers was extended to the fifth generation. Generation four (G4) was characterized by electrospray mass spectrometry. Thin films of generation five (G5) metallodendrimers were studied by tapping mode scanning force microscopy. Both on graphite and on mica spherical particles with a diameter of ca 15 nm were observed. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 6 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    A solid-state investigation of the desorption/evaporation of hindered phenols from low density polyethylene using FTIR and UV spectroscopy with integrating sphere: The effect of molecular size on the desorption (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 61 (1996), S. 1149-1162 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Low density polyethylene (LDPE) has been investigated with respect to the desorption/evaporation of hindered phenol antioxidants added to the polymer matrix. In this study, Fourier transform infrared and ultraviolet (FTIR and UV) spectroscopy without any extraction or refining steps in the analysis were used to measure the desorption constants. The UV spectrophotometer was equipped with an integrating sphere. The desorption constants, α, of five phenols containing the same 3,5-di-tert-butyl-4-hydroxyphenyl structure, but differing by the length of the hydrocarbon tails, were obtained in the temperature range of 40-100°C. The number of methylene groups in the tail varied between 0 and 17. The temperature-dependence of the phenols could be described by an Arrhenius type relationship. Very large differences in desorption rates were found due to differences in size of the antioxidants. © 1996 John Wiley & Sons, Inc.
    Additional Material: 19 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Gas-solid mass transfer in a jetloop reactor (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1187-1190 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420433
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  • 8
    Electronic Resource
    Electronic Resource
    Steric and Electronic Effects in the Diastereoselective Catalytic Epoxidation of Cyclic Allylic Alcohols with Methyltrioxorhenium (MTO) (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 785-790 
    Details
    ISSN: 1434-193X
    Keywords: Epoxidations ; Diastereoselectivity ; Allylic alcohols ; Homogeneous catalysis ; Methyltrioxorhenium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The steric effects of allylic substituents in the epoxidations with methyltrioxorhenium/urea/hydrogen peroxide adduct (MTO/UHP) have been assessed for a series of 3-alkyl-substituted cyclohexenes. The trans selectivity increases with the size of the substituent and the diastereoselectivities follow an excellent linear correlation with the steric substituent constants of Taft (Es) or Charton (ν). Good cis selectivity is observed in the epoxidation of the cyclic allylic alcohols 2-cyclopentenol and 2-cyclohexenol due to a hydroxy-directing effect through hydrogen bonding; however, for 2-cycloheptenol and 2-cyclooctenol hydrogen bonding is ineffective and steric interactions cause a higher trans selectivity. The conformationally fixed cis- and trans-5-tert-butyl-2-cyclohexenols serve as suitable substrates for gauging the dihedral angle of the transition states for the oxygen transfer in these epoxidations. Thus, the MTO/UHP oxidant favours a quasi-equatorial arrangement of the hydroxy group for effective hydrogen bonding (hydroxy-group directivity), in analogy to m-chloroperbenzoic acid (m-CPBA) and dimethyldioxirane (DMD), and a dihedral angle of ca. 130° is suggested.
    Additional Material: 2 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Optically Active Epoxy Diols by Titanium-Catalyzed Oxidation of Enantiomerically Enriched Hydroperoxy and Hydroxy Homoallylic Alcohols (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 907-912 
    Details
    ISSN: 1434-193X
    Keywords: Optically active epoxy diols ; Epoxidation ; Titanium catalysis ; High diastereoselectivity ; Optically active hydroperoxy and hydroxy homoallylic alcohols ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Ti-catalyzed epoxidation of optically active (S,S)-hydroperoxy homoallylic alcohols 2 affords the epoxy diol (S,R,S)-4 in high diastereoselectivity (d.r. up to 95:5), while the optically active hydroxy homoallylic alcohols (R,R)-3 are epoxidized by the β-hydroperoxy alcohol 5 under titanium catalysis to the corresponding epoxy (R,S,R)-diol 4 in a diastereomeric ratio up to 〉 99:1. This high diastereoselectivity is rationalized in terms of a rigid template for the oxygen transfer, in which the hydroperoxy alcohol 2 or 5 is ligated tridentately and the diol 3 bound bidentately to the titanium metal. Through these oxidative routes, both enantiomeric epoxy diols 4 are conveniently accessible.
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis of Optically Active α-Hydroxy Acids by Kinetic Resolution Through Lipase-Catalyzed Enantioselective Acetylation (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2013-2018 
    Details
    ISSN: 1434-193X
    Keywords: Lipase ; 2-Hydroxy acids ; Kinetic resolution ; Acetylation ; Biocatalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The lipase-catalyzed acetylation of a broad spectrum of racemic 2-hydroxy acids 1 to their 2-acetoxy acids 2 was shown to proceed with high enantioselectivity. Thus, the microbial lipases, in particular from Candidaantarctica and Burkholderiaspecies, are convenient biocatalysts for the synthesis of optically active 2-hydroxy acids in excellent enantioselectivity (ee values up to 〉 99%). The absolute configurations of the 2-hydroxy acids 1 were assigned by comparison of the gas-chromatographic data with that of literature-known reference compounds, or by means of the exciton-coupled circular dichroism method (ECCD) on their bichromophoric 2-naphthoate 9-anthrylmethyl derivatives 3. These results establish that (S)-2-hydroxy acids 1 were preferentially acetylated by microbial lipases.
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