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'Tautomerism' in keywords Facet   section ZfN Section B  [X]
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1Author    Requires cookie*
 Abstract    The reaction of imines with various electrophiles have afforded only N-alkylated products, contrary to earlier reports. While a large amount of work has been done on the synthetic applications of tertiary enamines, pioneered by S t o r k and coworkers1*2, less is known about the scope of similar applicability of secondary enamines. Secondary enamines predo­ minantly exist in the imino form both in aliphatic and in cyclic compounds except in cases where the R. R I tertiary enamine secondary enamine 
  Reference    (Z. Naturforsch. 30b, 128—131 [1975]; received September 13 1974) 
  Published    1975 
  Keywords    Imines, Enamines, Alkylation, Tautomerism 
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 TEI-XML for    default:Reihe_B/30/ZNB-1975-30b-0128.pdf 
 Identifier    ZNB-1975-30b-0128 
 Volume    30 
2Author    K. C. Dash, A. Schmidpeter++, H. Schmidbaur+Requires cookie*
 Title    Gold Complexes of a P-Coordinate Cyclotriphosphazene [1,2]  
 Abstract    Contrary to the reports on the coordination oi copper (I) to N/P-ambidentate cyclotri-phosphazenes, gold (I), gold (III) and dimethylgoldf 111) chloride are found to become exclusively P-coordinated to the prototype ligand 2-methyl-4,4,6,6-tetraphenylcyclotri-phosphazene (1). The P-H proton is transferred to an adjacent nitrogen atom of the heterocycle. According to temperature dependent NMR spectra, the AuCl and the AuClß complexes are fluxional molecules or ions, resp., with a rapid proton transfer between P-NH-P and P = N-P functions. The behaviour is similar to that of related palladium and platinum complexes, reported previously. 
  Reference    Z. Naturforsch. 35b, 1286—1288 (1980); eingegangen am 9. Juni 1980 
  Published    1980 
  Keywords    Gold Complexes, Cyclotriphosphazenes, N/P-Ambidentate System, Tautomerism 
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 TEI-XML for    default:Reihe_B/35/ZNB-1980-35b-1286.pdf 
 Identifier    ZNB-1980-35b-1286 
 Volume    35 
3Author    Latif Rateb, B. Azmy, M. A. Nashed, M. F. IskanderRequires cookie*
 Abstract    A series of benzoylacetaldehyde benzoylhydrazones were prepared and characterised. Their UV, IR, and iH NMR spectra suggest the enol-imine structure rather than the keto-imine form of analogous Schiff bases. The pKa values of these aroylhydrazones were also measured and correlated with the Hammet substitution constants. Attempted cyclizations of these open-chain aroylhydrazones afforded the corresponding 5-hydroxy-2-pyrazoline compounds rather than the expected pyrazoles. 
  Reference    Z. Naturforsch. 33b, 1527—1534 (1978); received July 24 1978 
  Published    1978 
  Keywords    Benzoylacetaldehyde Benzoylhydrazone, 5-Hydroxy-2-pyrazolines, UV, Tautomerism, Enol-imines 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-1527.pdf 
 Identifier    ZNB-1978-33b-1527 
 Volume    33 
4Author    M. Ikko Koskinen3, IlpoM. Utikainenb, Hannu EloaRequires cookie*
 Title    Crystal and Molecular Structure of Aminoguanidine Sulphate, an Important Enzyme Inhibitor and Starting Material of Drug Syntheses  
 Abstract    Aminoguanidine is not only an agent with a variety of pharmacological effects but also an im portant starting material of am idinohydrazone-type drugs and enzyme inhibitors. There­ fore, we have now synthesized am inoguanidine sulphate CN4H 82+.S 0 42~ and determined its structure by single-crystal X-ray diffraction. The doubly protonated (dication) form o f am ino­ guanidine that is present in the sulphate could, in principle, exist in the form of several differ­ ent tautom ers. The crystal studied consisted exclusively of one tautomer: one of the nitrogens of the hydrazine moiety bears three hydrogen atoms while the other one (the one bound to the carbon) bears one hydrogen. The other two nitrogens are bound to two hydrogens each. The predominance of this tautom er can be explained by the very strong resonance in it. The dica­ tion of aminoguanidine is remarkably planar. The hydrogens of the hydrazine moeity are, however, clearly out of the plane of the other atoms. There is a strong hydrogen bond between the proton of the m onoprotonated nitrogen and one sulphate oxygen. This bond obviously causes the deviation of the hydrogen from the plane. The bonds between the carbon atom and the adjecnt nitrogens are essentially equally long, indicating that each bond has approxim ately the same am ount of double bond character. One of the positive charges of the dication is thus delocalized, being shared by all of the atoms of the C N 3 moiety. In this respect, the structure is similar to that of all bis(amidinohydrazones) whose structures have been determined. The other positive charge of aminoguanidine dication is localized at the nitrogen bearing three hydrogens. 
  Reference    Z. Naturforsch. 49b, 556—560 (1994); received December 6 1993 
  Published    1994 
  Keywords    Bis(guanylhydrazones), Diamine Oxidase Inhibitors, Nitric Oxide Synthase Inhibitors, Resonance, Tautomerism 
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 TEI-XML for    default:Reihe_B/49/ZNB-1994-49b-0556.pdf 
 Identifier    ZNB-1994-49b-0556 
 Volume    49 
5Author    Jochen Ellermann, AlfonsA M DemuthRequires cookie*
 Title    Chemistry of Poly functional Molecules, 75 [1] The Reaction of 5-Bromo-uracil with Sodium Diphenylphosphide  
 Abstract    5-Bromo-uracil (1) reacts with sodium diphenylphosphide or a mixture of sodium diphenylphosphide and sodium amide in liquid ammonia to give sodium 5-bromo-uracilate (5 a). From water 5 a crystallizes with one mole H2O yielding 5b. Treatment of 5 a with D2O yields sodium 5-bromo-N-deutero-uracilate-D20 (1/1) (5 c). With chlorodiphenyl-phosphine 5a forms 1-diphenylphosphino-uracil (2). 5a, b, c show N(l)-N(3)-(H/D)-tauto-merism in concentrated D2O solutions already, but in DMSO or Dö-DMSO only in dilute solutions. All the compounds were characterized by infrared, Raman, X H NMR, UV spectra and conductometry. 
  Reference    Z. Naturforsch. 38b, 1568—1574 (1983); eingegangen am 6. Juni/2. August 1983 
  Published    1983 
  Keywords    Sodium 5-Bromo-uracilates, Deutero Derivatives, Tautomerism, NMR Spectra, UV Spectra, Vibrational Spectra 
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 TEI-XML for    default:Reihe_B/38/ZNB-1983-38b-1568.pdf 
 Identifier    ZNB-1983-38b-1568 
 Volume    38