ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
Filter
  • Ab initio calculations  (2)
  • Carbon dioxide fixation  (2)
  • 1
    ISSN: 1434-193X
    Schlagwort(e): Thia-aza heterocycles ; Bis(azolyl)alkanes ; 1-(Haloalkyl)pyridinium halides ; Synthetic methods ; Cyclization reactions ; Ab initio calculations ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Novel 5/6/5 heterocycles, 1,3,4-thiadiazolo[3,2-a]-1,3,4-thiadiazolo[3,2-d]-1,3,5-triazinium halides 7, have been synthesized by the reaction of 2-amino-1,3,4-thiadiazoles 6 with either 1-(haloalkyl)pyridinium halides 4 or N,N′-methylenebis(pyridinium) dibromides 5. The tricyclic compounds 7 are generated in the course of several successive reaction steps in which specific proton migrations, bond-breaking and bond-forming processes occur. The structures 7 have been verified by spectral data (1H and 13C NMR, MS), X-ray analysis and ab initio calculations. The latter show that both sp2-C atoms C(10) and C(12) of 7 are significantly positively charged and, therefore, exhibit electrophilic properties towards the primary amino group of the amino-thiadiazoles 6. In the course of a multi-step reaction cascade of the 6/7 mixture, novel multi-aza/thia heterocycles 8 are formed. The structures of the latter compounds have been confirmed by X-ray analysis as well as by detailed experimental and theoretical NMR-spectroscopic studies.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 2
    ISSN: 1434-193X
    Schlagwort(e): 4-Alkylidene-1,4-dihydropyridines ; 1-Acyl-4-benzylpyridinium tetrafluoroborates ; Carboxylic acid fluorides ; X-ray structures ; Ab initio calculations ; Density functional calculations ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 1-Acyl-4-benzylpyridinium salts 4 containing nonnucleophilic anions X- such as CF3SO3-, FSO3-, and BF4- can be generated quantitatively and in situ from 1-acyl-4-alkylidene-1,4-dihydropyridines 1a-f and the corresponding acid, HX. The BF4- salts reveal an interesting and unexpected thermal instability which allows the convenient synthesis of carboxylic acid fluorides 5b-f. This procedure offers advantages over known methods: All operations can be performed in a standard glass apparatus and do not require high pressures. The formation of RCOF 5 is assisted by the pyridine moiety of 4, which splits off and functions as a Lewis base to intercept the BF3 acid. The structural and electronic relationships as well as dominating differences between the very reactive cations of 4 and their almost “inert” uncharged precursors, the dihydropyridines 1, are discussed both on the fundament of experimental evidence (X-ray structures of 1f and the extremely reactive and very labile 4f) and theoretical investigations (ab initio and DFT MO calculations).
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 3
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 1055-1064 
    ISSN: 1434-1948
    Schlagwort(e): Carbon dioxide fixation ; Magnesium ; N ligands ; C-C coupling ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The reaction of oxalic amidines R1-N=C(NHR2)-C(NHR2)=N-R1 with CH3MgX followed by uptake of CO2 results in the formation of the trimeric carbamato complexes [R1-N=C(NR2-COO)-C(NR2COO)=N-R1]3Mg3(THF)6 (2a: R1 = R2 = Ph; 2b: R1 = R2 = p-tolyl) as the thermodynamically stable final products of the reaction. Their X-ray crystal structures show that the three metal centres are in a linear arrangement. The central magnesium ion is octahedrally surrounded by six O-donor atoms of the μ2-carbamato bridges, while both peripheral magnesium ions are facially coordinated by three O-donor atoms of the carbamato groups and three THF molecules. This coordination sphere can be considered as a structural model for the active centre in the ribulose-1,5-bisphosphate carboxylase/oxygenase enzyme. Compound 2a reacts with ZnCl2 or CoBr2, with CO2 elimination, to form dimeric complexes of the type [X2M(oxalamidinato)MX2][Mg(DMF)6] (M = Zn, Co; X = Cl, Br). X-ray crystal structure analyses show that the d-metals are tetrahedrally coordinated. The magnesium-bromide-containing intermediates in the formation of 2a and 2b are able to transfer CO2 to acetophenone, thus simulating the CO2 activation step in enzymatic biotin-dependent carboxylation reactions.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 4
    ISSN: 0009-2940
    Schlagwort(e): Carbon dioxide fixation ; 1-Azadiene ligands ; Nickel(0) complexes ; Carboxylation ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Organometallic CO2 Reservoires from Nickel(0)-1-Azadiene-Type Ligands and Their Reactivity in the Carboxylation of Acetophenone1-Azadiene-type ligands yield with nickel(0) binuclear organometallic compounds of the type [Ni(1-azadiene)n,]2 (n = 1, 2). The structures of the complexes 1 (n = 2, ligand A) and 3 (n = 1, ligand C) have been characterized by X-ray crystallography. 1 is unreactive towards CO2, 3 and similar compounds are able to react with CO2 to give metallacyclic carbamato complexes of Ni(II). In these compounds CO2 is activated and can carboxylate acetophenone to yield benzoylic acid upon protolysis. These reactions mimic biologic conversion reactions of CO2 into organic material by organometallics. - The addition of two moles of the (bpy)Ni(0)-fragment [from (bpy)Ni(COD)] to 3 gives the tetranuclear complex 6. The X-ray analysis of the monomeric model compound (bi-py)Ni(A) (11) shows that only the olefin part is coordinated. 6 and 11 can also react with CO2. Cu(I) complexes with 1-azadiene-type ligands are not reactive towards CO2.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...