- Formation of Benzoxathiete under Mild Conditions and Its Valence Tautomerism in Solution to Monothio-o-benzoquinone: An Experimental and Quantum Chemical Study
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Aprotic diazotization of 2-aniline in dimethoxyethane affords products that include biphenylene and dibenzo-1,4-oxathiane.Detection of these products is consistent with the formation of benzoxathiete and the valence tautomerism to monothio-o-benzoquinone with concomitant formation of dehydrobenzene by a competing pathway.The latter was independently trapped with 1,3-diphenylisobenzofuran and with 9,10-dimethylanthracene.The requirement for SO group participation in the formation of benzoxathiete is established by comparison with the behavior of the analogous thioether and sulfone compounds.EPR and spin-trapping experiments confirm the intermediacy of both oxygen- and nitrogen-centered free radicals which is consistent with the homolytic pathways proposed for the diazotization process.Parallel aqueous diazotization of 2-aniline affords vinyl acetate, phenol, and halobenzene consistent with the generation of dehydrobenzene but not benzoxathiete under these conditions.Spin-trapping/EPR studies gave no evidence for free-radical components in the protic diazotization reaction.Ab initio calculations using the 3-21G* and 6-31G* basis sets within the Hartree-Fock approximation, as well as the MP2/3-21G* method, predict an energetically feasible tautomerism of benzoxathiete to monothio-o-benzoquinone.The 3-21G* calculations reveal the presence of a biradical intermediate for this reaction which, as a singlet, features an energy higher than the benzoxathiete by 33 kcal/mol, while as the corresponding triplet it proves to be lower in energy than the benzoxathiete by 2.5 kcal/mol.This process, however, might be symmetry forbidden.By contrast, the symmetry-allowed cycloreversion pathway of benzoxathiete to dehydrobenzene and SO is energetically much less favorable.
- Naghipur, Ali,Reszka, Krzysztof,Sapse, Anne-Marie,Lown, J. William
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p. 258 - 268
(2007/10/02)
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- Process for producing aminophenyl-β-hydroxyethylsulfone
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A process for producing aminophenyl-β-hydroxyethylsulfone of the formula (I), STR1 which comprises the following steps: (1) condensing nitrohalobenzene with mercaptoethanol in the presence of an alkali hydroxide and at least one reaction medium selected from N-alkyl-substituted amides and sulfoxides to produce mononitrophenyl-β-hydroxyethylsulfide of the formula (II): STR2 (2) oxidizing the mononitrophenyl-β-hydroxyethylsulfide (II) to produce mononitrophenyl-β-hydroxyethylsulfone of the formula (III): STR3 and (3) reducing the mononitrophenyl-β-hydroxyethylsulfone to produce the aminophenyl-β-hydroxyethylsulfone of the formula (I). This compound is useful as an intermediate for aminophenyl-β-sulfatoethylsulfone represented by the following formula: STR4 which is an important intermediate for vinyl sulfone type reactive dyes largely used for dyeing cellulose fiber materials.
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