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  • 1
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The regioselectivity of transannular O-heterocyclization of cycloocta-1,5-diene (1) with phenylsulfenyl chloride and methanol or water, respectively, is determined by the oxy-component which acts as nucleophilic partner in the electrophilic three component reaction. The thermodynamically more stable endo, endo-2,6-bis(phenylsulfenyl)-9-oxabicyclo[3.3.1]nonane (2) is formed almost exclusively in methanol while the isomeric 9-oxabicyclo[4.2.1]nonane (3) is favored under kinetic control in the presence of water. The oxidation of 2 or 3 yields the bissulfones 4 and 5, respectively.
    Additional Material: 1 Ill.
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  • 2
    ISSN: 1434-193X
    Keywords: Carbene complexes ; 1-Metallahexatrienes ; Cyclopentadienes ; Carbene complexes ; Tungsten ; Domino cyclization ; Pentalenes ; Spirocyclopentanes ; Spiro compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -1,3-Dioxytetrahydropentalenes 9 have been generated by base-catalyzed addition of protic oxygen nucleophiles ROH 6a-g (RO = carboxy or phenyloxy) to the [2-(1-cyclopentenyl)ethynyl]carbene tungsten complex 3. Compounds 9 are highly reactive and afford (cyclobutenyl)carbene complexes 12a-g through spontaneous [2+2] cycloaddition to a second molecule of the (1-alkynyl)carbene complex 3. Thermolysis of compounds 12 was found to generate indeno[b]-spiro-tricyclo[5.3.0.0]decadienes 18 through π-cyclization of the 1-tungsta-1,3,5-hexatriene unit involving insertion of carbon monoxide into the W—C bond.
    Additional Material: 3 Ill.
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  • 3
    ISSN: 1434-193X
    Keywords: Ylides ; Wittig olefination ; Reaction mechanism ; Phosphorus-carbon coupling constants ; Substituent perturbation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of the ylide (cyclopropyl)3P=CH2 with Michler's thioketone S=C(C6H4NMe2)2 in [D5]pyridine gave the thio Wittig intermediate [(cyclopropyl)3P+-CH2-CAr2-S-] (11; 31P NMR: δ = +27.7). Compound 11 was characterized by X-ray diffraction and shown to exhibit a gauche-betaine-type structure with an S-C-C-P dihedral angle of 52.9(3)° and a P···S separation of 3.312(2) Å. The characteristic averaged 1JPCipso(aryl) coupling constant was used to elucidate the characteristic structural properties of Wittig and thio Wittig intermediates derived by treatment of the series Ph3P=CH2 (2a), Ph2MeP=CH2 (2b), and PhMe2P=CH2 (2c) with bis(p-methoxyphenyl) ketone to give 3 or benzophenone (to give 3′) or bis(p-methoxyphenyl) thioketone (to give 5), respectively. The oxaphosphetane series 3′a-3′c shows a strong response of the 1JPCipso(aryl) values (3a: 94 Hz; 3′b: 74 Hz; 3′c: 47 Hz) to this substituent perturbation, as it is expected for a dynamic trigonal-bipyramidal situation at the phosphorus atom, whereas the thio Wittig intermediate is only very little affected [1JPCipso(aryl) of 5a: 92 Hz; 5b: 86 Hz; 5c: 82 Hz]. Thus, the thio Wittig intermediates 5 seem to exhibit a pronounced phosphonium character in polar solvents and may be regarded as thiabetaine-type intermediates in solution.
    Additional Material: 1 Ill.
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  • 4
    ISSN: 1434-193X
    Keywords: Sultones ; Intramolecular Diels-Alder reaction ; Desulfurization ; Heterocycles ; Actic acids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A highly stereoselective and flexible sultone route to actic acids, the monomeric subunits of the macrotetrolides, has been developed and exemplified for nonactic acid (2a). Due to the extensive application of tandem transformations, only six steps were needed to secure methyl nonactate (20) from furan.
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  • 5
    ISSN: 0170-2041
    Keywords: Vilsmeier reaction, anomalous ; Pyrrolo[1,2-b]cinnoline, derivative ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diethyl Pyrrolo[1,2-b]cinnoline-6,8-dicarboxylate, a Product of an Anomalous Vilsmeier ReactionA byproduct of the Vilsmeier reaction of 1 has been shown by X-ray structure determination to be the pyrrolo[1,2-b]cinnoline 3. Informations concerning the mechanism of formation of 3 have been obtained from labeling experiments and an unequivocal assignment of NMR spectra.
    Additional Material: 5 Tab.
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  • 6
    ISSN: 0170-2041
    Keywords: Annulenes, hydrazino-bridged ; Vilsmeier formylation ; Pi systems, unstable ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrazino-Bridged Annulenes, 7.  -  Synthesis of Diethyl 6H-9b,9c-Diazacyclopenta[cd]phenalene-5,7-dicarboxylateThe 1,4-dihydropyridine 4 has been obtained from 1-amino-pyrrole and diethyl 2,6-dioxo-3,5-heptanedicarboxylate. Subsequent Vilsmeier reaction led to the aldehyde 7 which could be transformed into the tricyclic aldehyde 8b in a repeated Vilsmeier reaction. Final cyclization was achieved with sodium ethanolate yielding the extremly unstable diazacyclo-penta[cd]phenalene derivative 9.
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