143726-80-1Relevant articles and documents
From mutagenic to non-mutagenic nitroarenes: Effect of bulky alkyl substituents on the mutagenic activity of 4-nitrobiphenyl in Salmonella typhimurium. Part I. Substituents ortho to the nitro group and in 2'-position
Klein, Markus,Voigtmann, Ulrike,Haack, Torsten,Erdinger, Lothar,Boche, Gernot
, p. 55 - 68 (2007/10/03)
Eleven alkyl substituted derivatives of 4-nitrobiphenyl (4NBp) and two corresponding nitroso compounds were synthesised and tested for mutagenic potency in strains TA98 and TA100 of Salmonella typhimurium. The mutagenicity of compounds substituted ortho to the nitro group (3-methyl-, 3-ethyl-, 3-isopropyl-, 3-tertbutyl-, 3,5-diethyl-, 3,5-diisopropyl-, and 3,5-ditertbutyl-4NBp) decreased with growing steric demand of the alkyl substituents in both tester strains. The most sterically hindered compounds were non-mutagenic even at highest concentrations. This reduction of mutagenicity is correlated with deviations from the coplanar orientation of the nitro group relative to the aromatic plane. Since a comparable decrease of mutagenicity for the nitroso compounds (4NOBp and 3-tertbutyl-4NOBp) was not observed, the first reduction step of non-planar nitro groups must be inhibited.Alkyl groups in the 2'-position of 4NBp (2'-methyl-, 2'-ethyl-, 2'-isopropyl-, and 2',4',6'-trimethyl-4NBp) also reduced mutagenic activity with increasing size and removed it completely for the most sterically hindered species (2'-isopropyl-, 2',4',6'-trimethyl-4NBp). In this case, the co-planarity of the nitro group is not affected but the twisting of the two aromatic rings, which is associated with a less effective charge delocalisation of the nitrenium ion.The experimental mutagenicities of all nitro compounds were compared to predicted values, that are based on recently developed empirical equations. While there was reasonable correspondence for the parent compound (4NBp), its ortho methylated derivative (3-methyl-4NBp) and two highly hydrophobic dialkylated species (3,5-diisopropyl- and 3,5-ditertbutyl-4NBp), predictions for all other alkyl substituted compounds were too high. Thus, steric parameters should be included to improve the general validity of predictions by means of quantitative structure-activity relationships (QSAR). Copyright (C) 2000 Elsevier Science B.V.
Cobalt schiff base complex-catalyzed oxidation of anilines with tert-butyl hydroperoxide
Foerster, Stefan,Rieker, Anton,Maruyama, Kazushige,Murata, Kunihiko,Nishinaga, Akira
, p. 3320 - 3326 (2007/10/03)
Cobalt Schiff base complexes [Co(SB)] catalyze the oxidation of anilines (1) with tert-butyl hydroperoxide to give nitrobenzenes 2 and 4-(tert-butylperoxy)-2,5-cyclohexadien-1-imine derivatives 3 in yield distributions depending on the substitution mode of the substrate. 4-Alkyl- and 4-aryl-2,6-di-tert-butylanilines gave mixtures of 2 and 3, where the higher the bulkiness of the 4-substituent, the higher the yield of 2. With 2,4,6-trimethylaniline, the ratio of oxidations of the nitrogen and C-4 atoms was almost the same; but a hydrolyzed product 5 of the imine was obtained. 2,4,6-Triphenylaniline gave only 2. Nitrobenzene derivatives were also obtained from 2,6-dialkylanilines and 4-substituted anilines. The catalytic activity of Co(SB) depended on the nature of the SB ligand: the formal potential E° and steric factors seem to affect the reaction rate. Kinetic studies showed that the key step may involve hydrogen abstraction from the aniline, presumably by t-BuO? generated from homolytic decomposition of initially formed CoIII(SB)(OO-t-Bu). A precursor of 2 was found to be the nitrosobenzene derivative.
Co(salen) catalyzed oxidation of 2,4,6-trisubstituted anilines with tert-butylhydroperoxide
Nishinaga,Forster,Eichhorn,Speiser,Rieker
, p. 4425 - 4428 (2007/10/02)
Co(salen) catalyzed oxidation of 2,4,6-trisubstituted (preferentially 2,6-di-tert-butylated) anilines with tert-butylhydroperoxide gives 4-tert-butylperoxy-2,5-cyclohexadien-1-imine and nitrobenzene derivatives. The relative ratio of the products depends on the nature of the substituents in the substrate.