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  • 1
    Electronic Resource
    Electronic Resource
    Ideal enantiomeric resolution by recrystallization of a racemic compound (part 4): Relationship between enantiomeric resolution phenomenon and crystal properties (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 220-224 
    Details
    ISSN: 0899-0042
    Keywords: racemic compound crystal ; mixed crystal of (+) and (-) enantiomers ; enantiomeric enrichment in solution ; reversal of chirality ; X-ray powder diffraction ; chiral sulfonium sulfonate ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new example of a racemate showing unusual enantiomeric resolution phenomenon, in which simple recrystallization of the racemate leads to remarkable enantiomeric enrichment of either enantiomer up to 100% ee in the mother liquor, has been found. This compound is (±)-[2-[4-(3-ethoxy-2-hydroxypropoxy)phenylcarbamoyl]-ethyl]dimethylsulfonium p-nitrobenzenesulfonate [EtOCH2CH(OH)CH2OC6H4NHCOCH2CH2SMe2+O2NC6H4SO3-] [(±)-SN]. By repeating recrystallization of (±)-SN and the resulting deposited crystals successively and collecting the resulting enantiomerically enriched mother liquors with the same chirality sense, highly efficient enantiomeric resolution of the racemate into its separate enantiomers has been accomplished. The relationship between the occurrence of this enantiomeric resolution phenomenon and the crystal properties has been investigated with respect to SN and its aryl- and alkylsulfonate derivatives. The mode of enantiomeric resolution of (±)-SN was similar to that of para-substituted benzenesulfonate derivatives (±)-ST (4-MeC6H4SO3-) and (±)-SC (4-ClC6H4SO3-) previously reported, whereas the unsubstituted derivative (±)-SB (C6H5SO3-) and alkysulfonate derivatives (±)-SO (n-C8H17SO3-) and (±)-SM (CH3SO3-) did not show such an enantiomeric resolution phenomenon. The crystalline form of the former racemates that underwent the enantiomeric resolution was racemic compounds, while the latter were mixed crystals (solid solutions) composed of the respective optical antipodes. Chirality 9:220-224, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Enantiomeric separation and recognition mechanism of 2-arylpropionic acid derivatives by high-performance liquid chromatography using a chiral column (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 28-33 
    Details
    ISSN: 0899-0042
    Keywords: ibuprofen ; loxoprofen ; CS-670 ; loxoprofen and CS-670 trans-alcohols ; enantiomer ; diastereoisomer ; chiral HPLC ; chiral recognition ; NMR ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An optical resolution of the amide derivatives of ibuprofen and the carbamate-alkylester derivatives of the trans-alcohol metabolite of loxoprofen and an analogous compound, CS-670, was studied by chiral high-performance liquid chromatography (HPLC). The chiral columns SUMIPAX OA-4000 and OA-4100 were used to investigate the enantiomeric separation behavior of these derivatives using both reversed and normal mobile phases. A better separation factor (α) of the amide and the carbamate ester derivatives was obtained in the normal mobile phase than in the reversed mobile phase HPLC. In addition, the recognition mechanisms of both amide and carbamate ester enantiomers were investigated by 1H-nuclear magnetic resonance (NMR). It is suggested that the important driving forces for the enantiomeric separation are the formation of hydrogen bonding and the charge transfer complex between these derivatives and an active site of the chiral stationary phase. © 1995 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070106
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  • 3
    Electronic Resource
    Electronic Resource
    Role of 2-carboxyl substituent in the tautomerization between two equivalent enol forms of 3-hydroxyphenalenone (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 485-488 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The interconversion between two equivalent enol forms of 3-hydroxyphenalenone took place predominantly through a diketo form with a free energy of activation of ca 14 kcal mol-1 in DMSO solution determined by 125·8 MHz13C NMR measurement. On the other hand, the corresponding interconversion in 2-carboxy-3-hydroxyphenalenone was not frozen on the time scale of 13C NMR spectroscopy down to -60°C. This acceleration in the interconversion rate of the latter may be interpreted by a double proton switching between the hydrogen-bonded 2-carboxyl and 3-hydroxyenone moieties.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610030712
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  • 4
    Electronic Resource
    Electronic Resource
    MO study of the possibility of a concerted mechanism in the pinacol rearrangement (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 737-745 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The ab initio SCF-MO method was employed to examine the possibility of a reaction pathway without a carbocation intermediate in the pinacol rearrangement. The molecular geometries of the transition states were obtained for the 1,2-hydride shift together with H2O elimination, starting from the various methyl-substituted protonated 1,2-diols. It was found that the activation energies depend strongly on the substitutents. A comparison of the relative energies between β-hydroxycarbonium ions and the transition states of the concerted mechanism suggests that the stepwise mechanism is less favourable than the concerted path in each case.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610031107
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  • 5
    Electronic Resource
    Electronic Resource
    Photocyclisierungen von 1, 1'-Polymethylen-di-2-pyridonen. 46. Mitteilung über Photoreaktionen45. Mitt. siehe [1]. (1976)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 59 (1976), S. 2841-2854 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photocyclization of 1, 1′-Polymethylene-di-2-pyridones.Benzophenone sensitized irradiation of the four dipyridones 1-4 gave the internal photocyclization products 6 (64%, Scheme 4), 7 (60%, Scheme 5), 8 (Scheme 6), and 11 (26%, Scheme 7), respectively. The decamethylene compound 5 yielded only polymeric material.The primary [2+2] photoproduct 8 from dipyridone 3 (Scheme 6) is relatively unstable. Further irradiation or heating to 65° induced a Cope rearrangement to give compound 9 which, on heating to 137°, was converted into the isomeric compound 10. This product, as well as the other photoproducts mentioned, are rearranged back to their respective starting materials upon direct irradiation with 254 nm light or by heating to higher temperatures. The various possibilities for cycloadditions of pyridones are discussed as well as the possible factors which are responsible for the highly regioselective photoreactions of the dipyridones 1-4.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19760590822
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  • 6
    Electronic Resource
    Electronic Resource
    Intramolekulare Cycloadditionen in der Reihe der BinaphthyleTeilweise vorgetragen an der Herbstversammlung der Schweizerischen Chemischen Gesellschaft am 20.10.1973 in Lugano [1]. (1975)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 58 (1975), S. 1949-1977 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Intramolecular cyloadditions of binaphtyl compoundsThree new bridged ketones, 7,8 and 9, have been isolated in 44%, 3% and 19% yields respectively (Scheme 2) by heating 2,2′-bis-allyloxy-1,1′-binaphthyl (5) at 215° for 16 hours. These compounds could be epimerized about C(16) by bases, and in particular 9 yielded the new epimer 10. The structures of the alcohols obtained by reduction of the keto group are also given (Scheme 2). The constitution of all compounds was derived from spectroscopic data, chiefly from their 1H-NMR, spectra (tab. 2, 3 and fig. 1). The assignments were based on the observed long-range coupling constant between H(endo)-C(16) and H(endo)-C(5) in 7 and 10 and on the analysis of chemical shifts and coupling constants in both the ketones and their derivatives. Moreover, the structures of the compounds investigated have been proved by x-ray analysis of ketone 8 (chap. 3, fig. 2). The thermal conversion of binaphthylether 5 to the bridged ketones proceeds via an intramolecular Diels-Alder reaction, followed by Claisen rearrangement (Scheme 8). On heating, the bis-beta-methylallyl ether 20 yielded the ketone 21 and a small amount of the ether 23 (Schemes 5 and 7). Ether 23 and binaphthyl monoallyl ether 26 were converted thermally to the bridged ketones 31 (Scheme 7) and 27 (Scheme 6) respectively. In addition, 26 underwent an intramolecular ene-reaction to give the spiroketone 28 (Schemes 6 and 9). The structures of these compounds were also established, mainly by analysis of their 1H-NMR. spectra.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19750580711
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  • 7
    Electronic Resource
    Electronic Resource
    Intramolekulare Cycloaddition von [1,1′-Binaphthyl]-2,2′-bis(allylamin) (1977)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 60 (1977), S. 247-253 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Intramolecular cycloaddition of [1,1′-binaphthyl]-2,2′-bis(allylamine)Unlike the 1,1′-binaphthyl-2,2′-bis(allylether) the corresponding [1,1′-binaphthyl]-2,2′-bis(allylamine) (1) upon heating to 230° in mesitylene undergoes thermal decomposition only. However, when 1 is heated in a mixture of 2-methylaminoethanol and water, besides 3 the policyclic ketones 4 and 5 are formed in isolated yields of 28 and 10%, respectively (Scheme 1). Intermediates are the imines corresponding to 4 and 5 which are hydrolysed under the reaction conditions rather than decomposed. The imines are formed by a intramolecular Diels-Alder reaction, in which the double bond of one N-allylgroup reacts with the naphthalene ring of the second half of the molecule.The policyclic ketones 4 and 5 are characterized as acetates 6 and 7, respectively, and as the acetylated reduced products 11, and 12 and 13, respectively. The constitutions of all compounds are derived from spectroscopic data, chiefly from the 1H-NMR. spectra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19770600130
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  • 8
    Electronic Resource
    Electronic Resource
    Interaction Between Benzene and Naphthalenophane: In the Gas Phase and the Crystalline Lattice (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1769-1776 
    Details
    ISSN: 0947-3440
    Keywords: Naphthalenophane ; Clathrate ; Ab initio calculation ; Semiempirical calculation ; Edge-to-face interaction ; Phanes ; Arenes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction between naphthalenophane 1 and another aromatic compound in the gas phase was investigated by molecular orbital calculations, mainly focusing on the arrangement of both aromatic compounds and the effect of the substituents in the benzene ring. The X-ray crystallographic analysis of some clathrates of 1 with an aromatic solvent was also carried out in order to clarify the relationship between the gas and condensed phases. The most stable arrangement calculated for a complex of 1 and benzene or substituted benzene in the gas phase was found to be the arrangement in which the edges of the two naphthalene rings of 1 are directed to the face of the benzene ring. Such an arrangement was also observed in the clathrate crystals, according to the X-ray crystallographic analysis. This result suggests that the stable arrangement in the gas phase is probably maintained in solution, leading to the same arrangement in the crystals. The order of stabilization of the clathrates with some substituted benzenes is in agreement with that of the electron-donating ability of the functional group present in the benzene. A slight difference in the stabilization was observed between the complex with toluene and that with chlorobenzene, and such a difference is considered to affect the inclusion behavior of 1.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970821
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  • 9
    Electronic Resource
    Electronic Resource
    Stickstoffhaltige Dieisen-hexacarbonyl-Komplexe aus 3-Phenyl-2H-azirinen (1978)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 61 (1978), S. 589-606 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nitrogen-containing diiron-hexacarbonyl complexes from 3-phenyl-2H-azirinesReaction of 2,2-dimethyl-3-phenyl-2H-azirine (1) with diiron-enneacarbonyl yields as an insertion product, and in addition to other products, the diiron-hexacarbonyl complex 2 (Scheme 1), whose structure was derived from spectral data, in particular 13C-NMR.-data (Table 1). With trimethylamine oxide in benzene, 2 is converted into the urea derivative 3, and yields with cerium (IV) ammonium nitrate the nitrate 4 (Scheme 1). The analogous complexes 6 and 9 have been obtained by irradiation of 1-phenyl-vinyl azide (5) and ironpentacarbonyl (Scheme 1) and from vinyl isocyanate (8) and diiron-enneacarbonyl at 40° (Scheme 2), respectively.The azirine 1, an acetylenic compound and diiron-enneacarbonyl in benzene react to give complexes of type 10 as the main product (Scheme 3). The structure of complex 10 has been established by X-ray single crystals analysis. On the 13C-NMR. time scale the carbonyl groups of compound 10 show a fluxional behaviour: below -50° the CO-groups of one of the two Fe(CO)3-groups undergo intranuclear exchange, above -50° the CO-groups of both Fe(CO)3-groups undergo intranuclear exchange.Tentative reaction mechanisms for the formation of the complexes of type 2 and 10 are formulated in Schemes 5, 6 and 7.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19780610206
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  • 10
    Electronic Resource
    Electronic Resource
    Photochemische Reaktionen 115. Mitteilung [1]. Zur Photochemie konjugierter γ,δ-Epoxyenone: Der Einfluss eines Hydroxylsubstituenten in ∊-StellungMit den besten Wünschen Herrn Dr. Willy G. Stoll zum 70. Geburtstag zugeeignet (1980)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 63 (1980), S. 2230-2257 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemistry of Conjugated γ,δ-Epoxyenones: The Influence of a Hydroxy Substituent in ∊-PositionOn 1n, π*- or 1π,π*-excitation (λ ≥ 347 or λ=254 nm), the ε-hydroxy-γ;,δ-epoxyenone 8 undergoes fission of the C(γ)—O bond followed by the cleavage of the C(δ)-C(ε) bond. This hitherto unknown sequence of reactions is evidenced by the structure determination of the new type products 10-17 and 25, including a synthetic proof for 12 and the X-ray analysis of 11 (X-ray data: triclinic P1; a=7,386(2), b=8,904(4), c=9,684(5)Å; α=82,29(4)°, β=74,46(3)°, γ=82,29(3)°; Z=2).The selective 1π,π*-excitation also induces competitive C(γ)-C(δ) bond cleavage to yield the bicyclic acetal 18 and a ketonium-ylide intermediate a, which photochemically forms a carbene b giving the allene 19 and the cyclopropene 20.On 1n,π*-excitation of the acetate 9 the initial C(γ)-O bond fission is, in contrast to the behaviour of the corresponding alcohol 8, followed by a 1,2-methyl shift affording (E/Z)-28 or by a cyclization-autoxidation process yielding the lactone 29.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19800630813
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