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  • 1
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to developed a practical method for alkylating α-amino acids at the α- or β-carbon atom by intramolecular carbene C—H insertion, a series of diazoamides 3a-e was synthesized and subjected to rhodium(II) acetatecatalysed decomposition. The N-benzyl derivative 3a gave mainly the azetidinones 4a and 5a, resulting from a carbene C—H insertion into the N-benzyl group. The N-diphenylmethyl derivative 3c yielded, upon treatment with rhodium(II) acetate, the azetidinone 5c, the imine 6c, the cycloheptapyrrolidinone 7c as well as the desired pyrrolidinone 8c (12% yield) the latter resulting from an alkylation of the L-phenylalanine framework at the β-carbon atom.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that N-phenyl-substituted isothiazolium salts 2/3a-e with active 5-methyl or 5-methylene groups can easily be obtained by reaction of β-thiocyanatovinylaldehydes 1 and substituted anilines. Based on a wide variety of isothiazolium salts accessible in that way, a study of their various reaction products, e.g. 1,6-diphenyl-substituted thiadiazapentalenes 4a-d, 5a-j and special spiro compounds 6, and the influence of donor and acceptor substituents becomes possible. The structure of the basic skeleton of the thiadiazapentalenes was confirmed by X-ray analysis and ab initio MO calculations. Some mechanistic aspects are supported by the MO results.
    Additional Material: 1 Ill.
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  • 3
    ISSN: 0044-2313
    Keywords: Zirconium ; Lithium ; Hydroxoligands ; Oxoligand ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: An Unusual Trimeric Bimetallic Li—Zr Complex with the Backbone [Zr3(μ2-OH)3(μ3-O)Li5] by Reaction of Zirconiumorgano and Hydrido Complexes with WaterThe reaction of compounds of the type [(LZr)(LiH)(L′)]n and [(LZr)(LiH)(L′)(alkyne)]n (L: 2,2′-Biphenolato-dianion, L′: thf, Bu3P, alkyne: Ph—C≡C—SiMe3, CH≡CH) with water at 0°C in a thf solution results in the formation of th trimeric bimetallic complex 8 [(L2Zr)3(μ2-OH)3(μ3-O)Li5(thf)8(H2O)5] in 50% yield. The X-ray analysis of 8 shows that a planar six-membered ring Zr3(μ2-OH)3 is formed. In the middle of this ring is a dianionic oxygen atom placed, coordinating to the three L2Zr centres in a planar μ3-coordination (bond angles 120,05μ). Five lithium ions stabilize the anionic backbone by bridging the biphenolato chelate ligands, which form seven-membered chelate rings with the atoms.1H-, 13C-, and 7Li-NMR spectra exhibit that the solid state structure remains unchanged in solution (thf).
    Notes: Die Reaktion von Verbindungen des Typs [(LZr)(LiH)(L′)]n und [(LZr)(LiH)(L′)(alkin)]n (L: 2,2′-Biphenolato-dianion, L′: thf, Bu3P, alkin: Ph—C≡C—SiMe3, CH≡CH) mit Wasser führt bei 0°C in thf in 50% Ausbeute zum trimeren Bimetallkomplex 8 [(L2Zr)3(μ2-OH)3(μ3-O) Li5(thf)8(H2O)5]. Die Kristallstrukturanalyse von 8 zeigt, daß ein planarer Zr3(μ2-OH)3-Sechsring gebildet wird. In seiner Mitte ist ein dianionisches Sauerstoffatom fixiert, das an den drei L2Zr-Zentren mit planarer μ3-Koordination gebunden ist (Bindungswinkel Zr—O—Zr 120,05°). Fünf Lithiumionen stabilisieren das anionische Gerüst durch Verbrückung der Biphenolatchelatliganden, die mit den Zr-Atomen Chelatsiebenringe ausbilden. 1H-, 13C- und 7Li-NMR-Spektren zeigen, daß in Lösung (thf) die Festkörperstruktur unverändert erhalten bleibt.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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