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  • Organic Chemistry  (10)
  • Intramolecular vicarious nucleophilic substitution of hydrogen  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1988 (1988), S. 627-631 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reaktionen organischer Anionen, 139. - Stellvertretende Nucleophile Substitution von Wasserstoff in 1,2,4-Triazin-DerivatenCarbanionen mit Austrittsgruppen am anionischen Zentrum reagieren mit 1,2,4-Triazin und seinen Derivaten nach dem Muster der Stellvertretenden Nucleophilen Substitution: Wasserstoffatome in den Positionen 5, 3 oder 6 werden durch das Carbanion ersetzt. Es wird gezeigt, daß die Reaktivität der verschiedenen Triazin-Positionen gegenüber der nucleophilen Substitution des Wasserstoffs in der oben angegebenen Reihenfolge abnimmt. Die Reaktion bietet einen guten Zugang zu Triazinen mit funktionalisierten Alkylresten.
    Notes: Carbanions containing leaving groups at the carbanion centers react with 1,2,4-triazine and its derivatives according to the vicarious nucleophilic substitution scheme replacing hydrogen atoms in 5-, 3-, or 6-positions with the carbanion moiety. It is demonstrated that the activity of various positions of the triazine ring toward nucleophilic substitution of hydrogen decreases in this order. The reaction provides an efficient way of introduction of functionalized alkyl substituents into the triazine ring.
    Additional Material: 1 Tab.
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  • 2
    ISSN: 0170-2041
    Keywords: Carbanions ; Heptafulvenes ; Tropylium tetrafluoroborate ; Vicarious nucleophilic substitution ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tropylium tetrafluoroborate reacts with tertiary carbanions bearing leaving groups at the carbanionic center yielding covalent adducts. Some of them can be transformed into heptafulvenes or tropylium derivatives.
    Additional Material: 2 Tab.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1987 (1987), S. 711-715 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reaktionen mit organischen Anionen, 142. - Reaktion von α-Chloralkylsulfonen mit Nitronaphthalinen1- und 2-Nitronaphthaline reagieren mit Carbanionen, die sich von Chlormethyl(p-tolyl)sulfon und tert-Butyl(chlormethyl)sulfon ableiten, überwiegend oder ausschließlich unter „stellvertretender nucleophiler Substitution von Wasserstoff“ in Position 2 bzw. 1. Abweichende Substitutionsmuster oder manchmal anderes Reaktionsverhalten beobachtet man bei Umsetzungen mit tertiären Carbanionen aus α-Chlorpropyl(p-tolyl)sulfon.
    Notes: 1-and 2-nitronaphthalene derivatives react with the carbanions derived from chloromethyl p-tolyl sulfone and tert-butyl chloromethyl sulfone to give products of the vicarious nucleophilic substitution of hydrogen predominantly or exclusively in position 2 and 1, respectively. A different orientation pattern and sometimes other reaction pathways are observed in the reactions involving tertiary carbanions derived from α-chloropropyl p-tolyl sulfone.
    Additional Material: 2 Tab.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1990 (1990), S. 619-622 
    ISSN: 0170-2041
    Keywords: Electron-transfer ; Radical - Carbanion coupling ; Nitroalkylation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nitronate anions derived from primary and secondary nitroal-kanes undergo cross-coupling reactions with diethyl alkylmalonate anions in alcohol/DMF solution when treated with silver nitrate. A catalytic amount of chloride ions is necessary to promote selective reaction.
    Additional Material: 3 Tab.
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 412-420 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new rationalization of some phenomena in the phase-transfer catalysed processes promoted by concentrated aqueous alkali solutions, such as alkylations and β-eliminations, is proposed. It is predicted on the basis of adsorption theory and subsequently evidenced experimentally that the size of the interfacial area, controlled by the rate of stirring, affects the position of the extraction equilibrium of various anions with quaternary ammonium cations supplied by the phase-transfer catalysts.
    Additional Material: 3 Tab.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2229-2235 
    ISSN: 1434-193X
    Keywords: 3-Nitro-ω-benzylideneacetophenone ; Carbanions ; Michael addition ; Intramolecular vicarious nucleophilic substitution of hydrogen ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3-Nitro-ω-benzylideneacetophenone (1) reacts with carbanions containing leaving groups to give addition products to the electrophilic side chain. As a result of conjugated addition and subsequent intramolecular vicarious nucleophilic substitution of hydrogen (VNS) in the nitroaromatic ring of 1 in the position para to the nitro group, 4-cyano-7-nitro-3-phenyl-1,2,3,4-tetrahydronaphthalen-1-one and 4-cyano-7-nitro-3-phenylnaphth-1-ol are obtained. Smooth intramolecular VNS in the position para to the nitro group was observed for 4-chloro-1-(3-nitrophenyl)-3-phenyl-4-(p-tosyl)butanol.
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  • 7
    ISSN: 0947-3440
    Keywords: Nucleophilic aromatic substitution ; σ-Adducts ; Aromatic nitro compounds ; Heterocycles ; Carbanions ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Vicarious Nucleophilic Substitution (VNS) provides the possibility of the replacement of hydrogen atoms in electrophilic arenes with α-functionalized alkyl substituents. This review focuses on the transformations of products obtained by VNS, particularly into heterocyclic compounds. In addition, some characteristic features of the VNS mechanism are briefly described.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2337-2340 
    ISSN: 0947-3440
    Keywords: Carbanions ; Chloromethyl β-styryl sulfone ; Nitroarenes ; Phase-transfer catalysis ; Vicarious nucleophilic substitution ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chloromethyl trans-β-styryl sulfone carbanion reacts with benzaldehyde and acrylonitrile under phase-transfer catalysis conditions to give 2-phenyl-3-(trans-β-styrylsulfonyl)oxirane and bis(2-cyanoethyl)chloromethyl trans-β-styryl sulfone, respectively, and with nitroarenes to form the products of vicarious nucleophilic substitution of hydrogen.
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  • 9
    ISSN: 0170-2041
    Keywords: Nitropyrazole derivatives ; Vicarious nucleophilic Substitution ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Azoles, 261). - Vicarious Nucleophilic Substitution of Hydrogen in Nitropyrazole Derivatives4-Nitropyrazoles 1a-1c and 1g-1j react with the carbanion derived from chloromethyl p-tolyl sulfone (2) to give products of the vicarious nucleophilic substitution (VNS) of hydrogen at position 5. The presence of a second nitro group at position 3 (1c) or 2′ (1h) decreases the yield of the reaction considerably. 1d and 1e does not give products of VNS with 2. In 1f the substitution takes place at position 4. On treating with 2, 1h and 1j give the byproducts 3h1, 4/4a and 3j1, 3j2, 5, respectively.
    Notes: 4-Nitropyrazolderivate 1a-1c und 1g-1j reagieren mit dem Carbanion von Chlormethyl-p-tolylsulfon (2) unter stellvertretender nucleophiler Substitution von Wasserstoff in Position 5. Die Anwesenheit einer zweiten Nitrogruppe in Stellung 3 (1c) oder 2′ (1h) setzt die Ausbeute der Reaktion bedeutend herab. Aus 1d und 1e wurden keine Substitutionsprodukte erhalten. Bei 1f erfolgt die Substitution in Position 4. Bei der Einwirkung von 2 auf 1h und 1j entstehen die Nebenprodukte 3h1 und 4/4a bzw. 3j1, 3j2 und 5.
    Additional Material: 1 Tab.
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  • 10
    ISSN: 0170-2041
    Keywords: Carbanions ; Benzenes, 1-halo-2,4-dinitro- ; Vicarious nucleophilic substitutions (VNS) ; Sanger's reagent ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of carbanions of aryl chloromethyl and dichloromethyl sulfones 3 and 4 and tert-butyl chloro- and dichloroacetates (5 and 6) with 1-halo-2,4-dinitrobenzenes 1 and 2 proceed by nucleophilic replacement of a hydrogen atom. The SNAr of the halogen atom occurs to a negligible extent.
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