- A probable hydrogen-bonded meisenheimer complex: An unusually high S NAr reactivity of nitroaniline derivatives with hydroxide ion in aqueous media
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Observations show that nitroanilines exhibit an unusually high S NAr reactivity with OH- in aqueous media in reactions that produce nitrophenols. SNAr reaction of 4-nitroaniline (2a) in aqueous NaOH for 16 h yields 4-nitrophenol (4a) quantitatively, whereas a similar reaction of 4-nitrochlorobenzene (1a) gave 4a in 2% yield together with recovered 1a in 97%, suggesting that the leaving ability of the NH2 group far surpasses that of Cl under these conditions. An essential feature of SNAr reactions of nitroanilines is probably that the NH2 leaving group participates in a hydrogen-bonding interaction with H 2O. Density functional theory (DFT) calculations for a set of 4-nitroaniline, OH-, and H2O suggest a possible formation of a Meisenheimer complex stabilized by hydrogen-bonding interactions and a six-membered ring structure. The results obtained here contrast with conventional SNAr reactivity profiles in which nitroanilines are nearly unreactive with nucleophiles in organic solvents.
- Imoto, Mitsutaka,Matsui, Yasunori,Takeda, Motonori,Tamaki, Akihiro,Taniguchi, Hisaji,Mizuno, Kazuhiko,Ikeda, Hiroshi
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experimental part
p. 6356 - 6361
(2011/10/05)
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- Synthesis and characterization of selected 4,4′-diaminoalkoxyazobenzenes
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The role of the -N(CH2CH2OH)2 group in producing a mutagenic response from 4-((3-(2-hydroxyethoxy)4-amino)phenylazo)-N,N-bis(2-hydroxyethyl)aniline has been investigated. To accomplish this goal, a group of substituted 4,4′-diaminoazobenzene dyes was synthesized, and their structures were confirmed using 1H NMR, TOF-LC-ESI mass spectrometry, and combustion analysis. Mutagenicity was determined using the standard Ames test in Salmonella strains TA98, TA100, and TA1538 with and without S9 enzyme activation. The results of this study provide evidence that the mutagenicity of the parent dye arises from the metabolic cleavage of N-hydroxyethyl groups to give the corresponding -NHCH2CH2OH and -NH2 substituted monoazo dyes as direct-acting mutagens. All 5 of the dyes studied were mutagenic at various levels with and without S9 enzyme activation in TA1538. In addition, the results show that removing one N-hydroxyethyl group and capping both -OH groups in the parent dye did not affect mutagenicity, whereas removing both N-hydroxyethyl groups produced a strong direct-acting mutagen in all three bacterial strains. Increasing the length of the N-alkyl chain from two to three carbon atoms eliminated mutagenicity in TA98 without S9 activation.
- Jeong, Euigyung,Freeman, Harold S.,Claxton, Larry D.
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experimental part
p. 100 - 108
(2010/12/18)
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- A convenient method to aniline compounds using microwave-assisted transfer hydrogenation
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The reduction of mononitro and dinitro aromatic compounds to their aniline analogues using microwave-assisted transfer hydrogenation has been demonstrated. The optimised conditions used, with some examples, are described herein. Georg Thieme Verlag Stuttgart.
- Chapman, Nicholas,Conway, Benjamin,O'Grady, Fiona,Wall, Michael D.
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p. 1043 - 1046
(2007/10/03)
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- Possible Anthelmintic Agents: Syntheses of Various Imidazoquinazolinone Carbamates
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Two of the three possible imidazoquinazolinone-2-carbamates representing angular and linear heterocyclic systems, have been synthesised and evaluated for their anthelmintic activity.During the course of the synthesis of ethyl or methyl 7-alkylimidazoquinazolin-8-one-2-carbamate, it is observed that the reaction of 3-alkyl-7-chloro-6-nitroquinazolin-4-ones with butanol saturated with aq.NH3, furnishes a number of ring-opened products which have been characterised on the basis of elemental analyses, IR, PMR and mass spectral data.The same reaction when carried out with dry NH3, furnishes the desired amino-nitro derivatives.UV and IR spectra of the linear and angular imidazoquinazolinones have also been compared.
- Kumar, Shiv,Kansal, V. K.,Bhaduri, A. P.
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p. 1068 - 1071
(2007/10/02)
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