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  • 1
    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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  • 2
    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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    Paper (German National Licenses)
    Fulltext
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