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  • 1
    Electronic Resource
    Electronic Resource
    2,6-Disubstituted 4-Aminopyridines from 1,3-Dialkoxy-2-azapropenylium Salts and N-Methyl-4-piperidone EnaminesDedicated to Prof. D. Dr. Ernst Würthwein on the occasion of his 85th birthday. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1437-1440 
    Details
    ISSN: 0009-2940
    Keywords: 2-Azapropenylium salts, 1,3-dialkoxy- and 1,1,3,3-tetraalkoxy- ; Enamines of N-methyl-4-piperidone ; 4-Aminopyridines ; 3,7-Diazabicyclo[3.3.1]non-2-en-9-ones ; Retro-Mannich reaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,3-Dialkoxy-2-azapropenylium salts 1 react with enamines 2 of N-methyl-4-piperidone at room temperature to give 2,6-disubstituted 4-aminopyridines 4, 5 in low to moderate yield after hydrolysis. Intermediates of the reaction of 1a with 2 are the bicyclic iminium salts 6 and 7, which may be detected 1H-NMR spectroscopically prior to hydrolysis. Hydrolysis of the mixture obtained from the reaction of 1a with 2a under basic conditions furnishes the bicyclic ketone 3 as the major product. A “retro-Mannich”-type reaction is suggested to explain the degradation of the bicyclic intermediates 6, 7 with the formation of the pyridines 4, 5.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270817
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  • 2
    Electronic Resource
    Electronic Resource
    3-Azabicyclische Ketone durch Reaktionen von 1,3-Diethoxy-2-azapropenylium-Salzen mit Enaminen cyclischer Ketone (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 133-141 
    Details
    ISSN: 0009-2940
    Keywords: 2-Azapropenylium salts ; Enamines ; 3-Azabicyclo[3.2.1]oct-2-en-8-ones ; 3-Azabicyclo[3.3.1]non-2-en-9-ones ; Stereochemistry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3-Azabicyclic Ketones from 1,3-Dialkoxy-2-azapropenylium Salts and Enamines of Cyclic Ketones1,3-Diethoxy-2-azapropenylium salts 1 are powerful biselectrophiles and react diastereoselectively with enamines of five-membered ring ketones 2 to yield novel 3-azabicyclo[3.2.1]oct-2-en-8-one 5 after hydrolysis of the intermediate iminium salts 3, 4. Some of the iminium salts 3 can be hydrolyzed further to provide the diketo imines 6. With enamines of six-membered ring ketones 7 the 3-azabicyclo[3.3.1]non-2-en-9-ones 10, 11 are obtained after hydrolytic workup. Mixtures of diastereomers 10/11 are found in the case of 7a, b, whereas with 7g  -  j the endo-phenyl derivatives 10 are formed exclusively. With the unsymmetrical enamine 7b only one regioisomer is observed. The decalone enamine 12 reacts with 1a to yield the tricyclic iminium salt 13.  -  The configuration of the bicyclic products has been determined by using NMR spectroscopic techniques (COSY, polarisation transfer by long range couplings); an X-;Ray analysis of compound 10a is used as basis for the NMR assignments. General rules for the determination of the stereochemistry of these azabicyclic systems by 1H-NMR shift arguments are derived.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260121
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