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  • 1
    Electronic Resource
    Electronic Resource
    Heterocyclization Reactions of Conjugated Heterocumulenes. Synthesis of Pyridine Derivatives by a Tandem Aza Wittig/Electrocyclization Strategy (1989)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 307-313 
    Details
    ISSN: 0009-2940
    Keywords: Aza Wittig reaction ; Heterocumulenes, conjugated ; Pyridine derivatives ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cyclisierungsreaktionen von konjugierten Heterocumulenen. Synthese von Pyridinderivaten durch Tandem-Aza-Wittig/Elektro-Ringschluß-StrategieDie Aza-Wittig-Reaktion der Iminophosphorane 3 mit Isocyanaten führt zu konjugierten Carbodiimiden 4, die elektrocyclisch 2-Pyridincarbonsäureester 5 ergeben. Iminophosphoran 9 reagiert mit Nitromethan bzw. Aceton im Molverhältnis 1:1 zu 10 bzw. 11. Aus 9 und Nitromethan 1:3 entsteht das Iminophosphoran 12. Dessen Struktur wurde durch Kristallstrukturanalyse bewiesen. Die Iminophosphorane 10, 11 reagieren mit Isocyanaten oder Kohlendioxid zu den Pyrazolo[3,4-b]pyridinen 13, 15 bzw. 14, 16.
    Notes: The aza Wittig reaction of iminophosphorane 3 with isocyanates leads to conjugated carbodiimides 4, which undergo electrocyclic ring closure to give ethyl 2-pyridinecarboxylates 5. Iminophosphorane 9 reacts with nitromethane and acetone in a 1:1 molar ratio to form 10 and 11, respectively. Reaction of 9 with nitromethane in 1:3 molar ratio yields the iminophosphorane 12. The structure of 12 has been established by X-ray crystallography. Iminophosphoranes 10 and 11 react with isocyanates or carbon dioxide to give the pyrazolo[3,4-b]pyridines 13, 15 and 14, 16, respectively.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19891220217
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  • 2
    Electronic Resource
    Electronic Resource
    Preparation of [5 + 6]-, [6 + 6]-, and [6 + 7]-Bicyclic Guanidines from C,C'-Bis(iminophosphoranes) (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1641-1652 
    Details
    ISSN: 0009-2940
    Keywords: Bis(iminophosphoranes) ; Guanidines, bicyclic ; Aza Wittig reaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A one-pot synthesis of [5 + 6]-, [6 + 6]-, and [6 + 7]-rigid bicyclic guanidines (6, 8, 19, 21, 23) based on a bis(iminophosphorane)-mediated annulation strategy is reported. The crystal and molecular structure of the parent [5 + 6]-bicyclic guanidine 8 has been established by X-ray diffraction. The crystallographically independent molecule forms dimers through a centre of symmetry by N-H-N hydrogen bonds. The molecule, and therefore the dimer, is statistically disordered in a 65/35 ratio. A statistical study of N-H-N hydrogen bonds of this kind of dimers has been carried out by using the Cambridge Structural Database.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270916
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  • 3
    Electronic Resource
    Electronic Resource
    Carbon-13 NMR study of 5-triphenyl-phosphoranilydeneaminopyrazoles (1991)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 29 (1991), S. 517-520 
    Details
    ISSN: 0749-1581
    Keywords: 13C NMR ; Chemical shifts ; J(CP) ; N-Phenylpyrazoles ; Iminophosphoranes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C chemical shifts and 13C-31P coupling constants are reported for nineteen pyrazoles bearing an N=PPh3 substituent at position 5. The three heterocyclic carbons are coupled with the phosphorus (2J, 3J and 4J). These couplings are very sensitive to the nature of the subtituent at position 4 [CHO, CH=CHCOMe, CH(CH2NO2)2, CH=NR, CH2NHR and CH2N(COR)Ar].
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260290519
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    Paper (German National Licenses)
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