- Substituent effects on the electrophilic activity of nitroarenes in reactions with carbanions
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The effect on electrophilic activity of substituents located para, ortho, and meta to the nitro group of nitrobenzenes was determined by using vicarious nucleophilic substitution of hydrogen (VNS) with the carbanion of chloromethyl phenyl sulfone (1) as the model process. Values for the relative activities of substituted nitroarenes are given relative to nitrobenzene, which was taken as the standard. This process was chosen as a model reaction because it meets key criteria, such as the wide range of substituents that can be present on the nitrobenzene ring, a low sensitivity to steric hindrance, and in particular the possibility of ensuring conditions in which the overall relative rates of reaction in competitive experiments are equal to the relative rates of nucleophilic addition. The values of relative rates of addition, which were taken to be a measure of electrophilic activity, were determined by competitive experiments in which pairs of nitroarenes competed for the VNS reaction with carbanion of 1. A comprehensive set of data for effects of substituents on the electrophilic activity of nitroarenes is presented for the first time.
- Blazej, Sylwia,Makosza, Mieczyslaw
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supporting information; experimental part
p. 11113 - 11122
(2009/11/30)
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- SPECIFIC ORTHO ORIENTATION IN THE VICARIOUS SUBSTITUTION OF HYDROGEN IN AROMATIC NITRO COMPOUNDS WITH CARBANION OF CHLOROMETHYL PHENYL SULFONE
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Vicarious nucleophilic substitution of hydrogen atoms in nitroarenes with chloromethylphenyl sulfone proceeds selectively ortho to the nitro group when carried out in t-BuOK/THF base/solvent system.In the majority of 3-substituted nitrobenzene derivatives substitution occurs at the most hindered position 2.These conditions offer an efficient method of synthesis of 2,6 and 2,3-disubstituted nitrobenzene derivatives.
- Makosza, M.,Glinka, T.,Kinowski, A.
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p. 1863 - 1868
(2007/10/02)
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- Vicarious Nucleophilic Substitution of Hydrogen in Nitroarenes with Carbanions of α-Haloalkyl Phenyl Sulfones
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Carbanions of α-chloroalkyl phenyl sulfones and N,N-dialkyl-α-chloroalkanesulfonamides react with nitrobenzenes to effect direct nucleophilic replacement of hydrogen ortho and para to the nitro group, with vicarious loss of chloride anion, to give the corresponding nitrobenzylsulfonyl derivatives.The reaction occurs much more rapidly than the replacement of such good leaving groups as halogen, methoxy, and phenoxy.Most substituents in the nitrobenzene ring do not interfere with the reaction.The effect of substituents in the nitrobenzene and the carbanion on the orientation of the substitution is discussed.
- Makosza, Mieczyslaw,Golinski, Jerzy,Baran, Janusz
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p. 1488 - 1494
(2007/10/02)
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