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Chaikovski, Vitold K.; Филимонов, В. Д.; Yagovkin, A. Yu.; Огородников, В. Д.

doi:10.1023/a:1015047916151

Cited by 6 publications

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References 6 publications

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“…The vast ma jority of the published studies ignores this question, but transfer of iodine from NIS and TIG to solutions of trifluoromethanesulfuric and sulfuric acids was detected experimentally. 3, 14 In this study, based on the calculated thermodynamic characteristics, we first calculated the changes in the free energy of iodine transfer from ICl, NIS, and NISAC to H 2 O, MeOH, and H 2 SO 4 in the gas phase and in solution in MeOH (Table 4). To estimate the effect of the nature of halogen on these exchange processes, identical calculations were carried out for NBS and NCS.…”

Section: Methodsmentioning

confidence: 99%

Electronic structures and reactivities of iodinating agents in the gas phase and in solutions: A density functional study

et al. 2006

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The electronic and spatial structures of a broad spectrum of neutral compounds with X-Hal (X = N, O, Cl; Hal = Cl, Br, I) bonds and their protonated forms and of differ ent electronic states of triiodide cation, I 3 + , were determined from density functional B3LYP/6 311G* quantum chemical calculations. The effects of the structure of these com pounds on the parameters of electrophilic reactivity were revealed and the thermochemical characteristics of homolytic and heterolytic X-Hal bond dissociation and of iodine transfer in hydroxyl containing solvents were calculated. Due to low homolytic bond dissociation ener gies of X-I, the formation of molecular iodine and triiodide cation I 3 + becomes thermody namically favorable and the cation should act as iodinating agent alternative to acylhypoiodites and N iodoimides. The solvation effects of MeOH and CH 2 Cl 2 on the X-Hal bond homolysis and heterolysis were determined using the PCM model.

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Section: Methodsmentioning

confidence: 99%

Electronic structures and reactivities of iodinating agents in the gas phase and in solutions: A density functional study

et al. 2006

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“…We examined the behavior of compound I in reaction with 2,4,6,8-tetraiodo-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione (II) in acetonitrile and organic acids, acetic (in the presence of sulfuric) and trifluoroacetic. We previously showed that tetraiodoglycoluril II is a soft iodinating agent which readily reacts with polyalkylbenzenes in the temperature range from 0 to 20°C [9]. In order to avoid ipso-substitution, we tried to react trialkylbenzene I with glycoluril II in acetonitrile in the absence of acid.…”

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Reaction of 1,3,5-tri-tert-butylbenzene with 2,4,6,8-tetraiodo-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione

et al. 2012

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Reactions of 1,3,5-tri-tert-butylbenzene with 2, 4,6,8-tetraiodo-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione in acetic and trifluoroacetic acids involve substitution of one or two tert-butyl groups in the aromatic ring with formation of mono-, di-, and triiodo-substituted derivatives. No iodo derivatives are formed in acetonitrile.Iodo derivatives of trialkylbenzenes are convenient models for studying steric effects of substituents and deformations of the benzene ring. Direct iodination of trimethylbenzene (mesitylene) readily occurs with formation of iodo derivatives in high yield, whereas introduction of iodine into benzene ring containing tert-butyl groups involves some specificity. Monosubstituted tert-butylbenzene undergoes smooth iodination [1-6], while iodination of di-tert-butylbenzenes is not selective, and it leads to the formation of a considerable amount of ipso-substitution products [1,5]. This is especially typical of 1,4-di-tert-butylbenzene [1,5]. Direct iodination of 1,3,5-tri-tert-butylbenzene (I) was not studied.tert-Butyl groups in compound I can be replaced even in the bromination process, in particular in acid medium. According to [7], the bromination of I with acetyl hypobromite generated in situ by reaction of bromine with silver perchlorate in acetic acid yields not only 1,3,5-tri-tert-butyl-2-bromobenzene but also acetoxylation product, 2,4,6-tri-tert-butylphenyl acetate and products of replacement of one tert-butyl group by the halogen atom or acetoxy group, the substrate conversion being 55%. Even more complex mixture of compounds, including ipso-substitution and diarylation products, was obtained in the bromination of I with 2,4,6,8-tetrabromo-2,4,6,8-tetraazabicyclo-[3.3.0]octane-3,7-dione [8].The calculated (PM3) enthalpies of electrophilic (S E ) and ipso-iodination (S i ) of compound I, ΔH = 500.90 and -258.95 kJ/mol, respectively, indicate that ipso-iodination is thermodynamically more favorable than electrophilic iodination. We examined the behavior of compound I in reaction with 2,4,6,8-tetraiodo-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione (II) in acetonitrile and organic acids, acetic (in the presence of sulfuric) and trifluoroacetic. We previously showed that tetraiodoglycoluril II is a soft iodinating agent which readily reacts with polyalkylbenzenes in the temperature range from 0 to 20°C [9].

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“…Iodinating reagents possessing iodine-heteroatom bonds include: iodine chloride (ICl), hypoiodites (HOI, CH 3 COOI, CF 3 COOI, HSO 3 OI, TsOI, TfOI), N-iodo imides (N-iodosuccinimide [1], N-iodosaccharin [2], 1,3-diiodo-5,5-dimethylhydantoin [3], tetraiodoglycoluril [4]), and N-iodoacetamide [5]. Iodine chloride, N-iodo imides, and N-iodoacetamide are fairly stable compounds, whereas hypoiodite-like compounds are only postulated as independent iodinating species generated in situ from iodinating reagent and the corresponding acid.…”

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Quantum-chemical study on the relation between thermodynamic parameters in the iodination of benzene with N-I and O-I reagents and pK a values of the corresponding NH and oh acids

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Chaikovskii

2010

Russ J Org Chem

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Thermodynamic parameters of direct iodination of benzene with several iodinating agents were calculated using semiempirical (PM3), ab initio (3-21G**), and DFT (B3LYP/LanL2DZ) methods, as well as in terms of the polarization continuum model (PCM or Tomasi model). A close to linear correlation was found between the calculated thermodynamic parameters (ΔH ≠ , ΔG ≠ ) and pK T and experimental pK a values of acids whose anions are incorporated into iodine-containing intermediates.Methods for direct iodination of aromatic compounds may be divided into two large groups. The first group includes procedures utilizing a combination of molecular iodine and an oxidant, and the set of available oxidants is very wide. Methods of the second group are based on the use of compounds having an iodine-heteroatom bond. Strong electronegativity of the heteroatom in such compounds induces a partial positive charge on the iodine atom, so that its electrophilicity increases. Examples of oxidative iodinating systems are I 2 -HNO 3 -H 2 SO 4 -AcOH, I 2 -oleum, I 2 -CrO 3 , I 2 -HgO, I 2 -HIO 3 , I 2 -HIO 4 , I 2 -KMnO 4 , I 2 -CH 3 CO 3 H, I 2 -PhI(OCOCF 3 ) 2 , etc.[1]. Most of these systems are capable of iodinating not only activated but also some deactivated arenes. In all cases, oxidation of molecular iodine with formation of electrophilic intermediates like I + or I 3 + is assumed.Iodinating reagents possessing iodine-heteroatom bonds include: iodine chloride (ICl), hypoiodites (HOI, CH 3 COOI, CF 3 COOI, HSO 3 OI, TsOI, TfOI), N-iodo imides (N-iodosuccinimide [1], N-iodosaccharin [2], 1,3-diiodo-5,5-dimethylhydantoin [3], tetraiodoglycoluril [4]), and N-iodoacetamide [5]. Iodine chloride, N-iodo imides, and N-iodoacetamide are fairly stable compounds, whereas hypoiodite-like compounds are only postulated as independent iodinating species generated in situ from iodinating reagent and the corresponding acid. It is well known that ICl, N-iodo imides, and N-iodoacetamide are weak iodinating agents, and their activity considerably increases upon addition of strong acids such as sulfuric, trifluoroacetic, trifluoromethanesulfonic, etc. For example, N-iodosuccinimide in one of the strongest acids, trifluoromethanesulfonic acid, is capable of iodinating deactivated arenes, in particular nitrobenzene, at room temperature due to formation of iodine trifluoromethanesulfonate ISO 3 CF 3 as a hypoiodite-like species [6]. Enhancement of the reactivity of N-iodosucinimide was also observed in the presence of CF 3 COOH [7] and H 2 SO 4 [8,9], presumably due to generation in situ of CF 3 COOI and IOSO 3 H. This may be illustrated by Scheme 1 where HY is a protic acid, and IY is a hypoiodite-like species with enhanced electrophilicity. Likewise, 1,3-diiodo-5,5-dimethylhydantoin [9] and tetraiodoglycoluril [10] were reported to behave similarly in concentrated sulfuric acid.Although available experimental data show that the electrophilicity of iodine species generated in strongly acidic medium considerably increases, no quantitative studies were perf...

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Cited by 6 publications

References 6 publications

Electronic structures and reactivities of iodinating agents in the gas phase and in solutions: A density functional study

Electronic structures and reactivities of iodinating agents in the gas phase and in solutions: A density functional study

Reaction of 1,3,5-tri-tert-butylbenzene with 2,4,6,8-tetraiodo-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione

Quantum-chemical study on the relation between thermodynamic parameters in the iodination of benzene with N-I and O-I reagents and pK a values of the corresponding NH and oh acids

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