Urazole

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Waldemar Adam - One of the best experts on this subject based on the ideXlab platform.

  • direct amination of olefins through sequential triazolinedione ene reaction and carbanion assisted cleavage of the n n Urazole bond
    Organic Letters, 2000
    Co-Authors: Waldemar Adam, Aurelia Pastor, Thomas Wirth
    Abstract:

    Allylic amines 5 are obtained in 30−55% overall yields by the base-catalyzed hydrolysis of trialkylated allylic Urazoles 3; the latter are prepared by the TAD ene reaction of the appropriate olefin and further N-alkylation with α-bromoacetophenone. The proposed mechanism for this novel Urazole rupture is based on the generation of a carbanion adjacent to the hydrazide functionality, which induces Urazole ring-opening by cleavage of the N−N bond.

  • detection of phenyl substituted radical cations derived from cyclopentyl and Urazole type azoalkanes by pulse radiolysis influence of heteroatom substitution on the radical cation reactivities
    Journal of the American Chemical Society, 1997
    Co-Authors: Waldemar Adam, Thomas Kammel, Marion Toubartz, Steen Steenken
    Abstract:

    The radical cations of cyclopentane- and Urazole-annelated azoalkanes and housanes were generated by pulse radiolysis and the transients characterized spectrally and kinetically by time-resolved optical monitoring. For the bridgehead-substituted diphenyl derivatives of the cyclopentane-annelated azoalkane 1 and housane 2 only the corresponding proximate 1,2 radical cation species were observed, generated from the initially formed and too short-lived (<1 μs) distonic 1,3 radical cation by 1,2-methyl migration. In contrast, for the corresponding Urazole-annelated azoalkanes 4, the initial distonic 1,3 radical cations 5•+ were detected, and of these the methyl-substituted 5b•+ deprotonates to the radical 5b•.

  • generation of 4 5 diazacyclopentane 1 3 diyl radical cations by chemical electron transfer cet oxidation of Urazole bridged bicyclic housanes bicyclo 2 1 0 pentanes and their chemical transformations
    ChemInform, 1996
    Co-Authors: Waldemar Adam, Thomas Kammel
    Abstract:

    4,5-Diazacyclopentane-1,3-diyl radical cations 3(*)(+)() were generated from Urazole-bridged bicyclic housanes 3 through chemical oxidation by using tris(4-bromophenyl)aminium hexachloroantimonate as oxidant to afford the two olefinic products 4 and 5. Product studies establish that the bisolefins 5 are the result of double oxidation of the housanes 3, whereas the monoolefins 4 are formed by acid-catalyzed rearrangement, which can be suppressed by excess of base (2,6-di-tert-butylpyridine). In the case of dibenzyl substitution (3c), disproportionation of two monoradical species 5(H)c(*) serves as an alternative pathway to the corresponding olefins 4 and 5 because higher amounts of double oxidation product were isolated in the absence of base than expected if only a stoichiometric reaction were operating. Semiempirical MO calculations suggest that ionization takes place from one of the nitrogen lone pairs rather than from the strained central C-C bond as implied by the significantly lower (by ca. 0.5 eV) ionization potential. Furthermore, in the initially puckered radical cation, the positive charge is mainly located at the two nitrogen atoms, while after relaxation to the planar geometry, the charge shifts essentially entirely to the radical cation carbon atoms. The trapping reaction with methanol leads to the hemiaminal-type products 6 and 7, which establish the involvement of the cationic intermediates 3(H)(+)() and 5(H)(+)(). In addition, (13)C NMR spectroscopy confirmed these cationic intermediates [3(H)(+)() and 5(H)(+)()] by detection of the characteristic signals below delta 250 for carbenium ions. Unquestionably, the Urazole ring significantly influences the radical cation reactivity of the housanes 3. Thus, in contrast to the corresponding homocyclic tricyclooctane derivatives, stoichiometric instead of catalytic amounts of CET oxidant are needed, the two nitrogen atoms of the hydrazino bridge stabilize the radical cation 3(*)(+)() by conjugation, and the carbonyl groups of the Urazole moiety assist the deprotonation to the exocyclic double bonds to prevent 1,2 alkyl migration.

  • generation of 4 5 diazacyclopentane 1 3 diyl radical cations by chemical electron transfer cet oxidation of Urazole bridged bicyclic housanes bicyclo 2 1 0 pentanes and their chemical transformations
    Journal of Organic Chemistry, 1996
    Co-Authors: Waldemar Adam, Thomas Kammel
    Abstract:

    4,5-Diazacyclopentane-1,3-diyl radical cations 3•+ were generated from Urazole-bridged bicyclic housanes 3 through chemical oxidation by using tris(4-bromophenyl)aminium hexachloroantimonate as oxidant to afford the two olefinic products 4 and 5. Product studies establish that the bisolefins 5 are the result of double oxidation of the housanes 3, whereas the monoolefins 4 are formed by acid-catalyzed rearrangement, which can be suppressed by excess of base (2,6-di-tert-butylpyridine). In the case of dibenzyl substitution (3c), disproportionation of two monoradical species 5(H)c• serves as an alternative pathway to the corresponding olefins 4 and 5 because higher amounts of double oxidation product were isolated in the absence of base than expected if only a stoichiometric reaction were operating. Semiempirical MO calculations suggest that ionization takes place from one of the nitrogen lone pairs rather than from the strained central C−C bond as implied by the significantly lower (by ca. 0.5 eV) ionizatio...

Thomas Kammel - One of the best experts on this subject based on the ideXlab platform.

  • detection of phenyl substituted radical cations derived from cyclopentyl and Urazole type azoalkanes by pulse radiolysis influence of heteroatom substitution on the radical cation reactivities
    Journal of the American Chemical Society, 1997
    Co-Authors: Waldemar Adam, Thomas Kammel, Marion Toubartz, Steen Steenken
    Abstract:

    The radical cations of cyclopentane- and Urazole-annelated azoalkanes and housanes were generated by pulse radiolysis and the transients characterized spectrally and kinetically by time-resolved optical monitoring. For the bridgehead-substituted diphenyl derivatives of the cyclopentane-annelated azoalkane 1 and housane 2 only the corresponding proximate 1,2 radical cation species were observed, generated from the initially formed and too short-lived (<1 μs) distonic 1,3 radical cation by 1,2-methyl migration. In contrast, for the corresponding Urazole-annelated azoalkanes 4, the initial distonic 1,3 radical cations 5•+ were detected, and of these the methyl-substituted 5b•+ deprotonates to the radical 5b•.

  • generation of 4 5 diazacyclopentane 1 3 diyl radical cations by chemical electron transfer cet oxidation of Urazole bridged bicyclic housanes bicyclo 2 1 0 pentanes and their chemical transformations
    ChemInform, 1996
    Co-Authors: Waldemar Adam, Thomas Kammel
    Abstract:

    4,5-Diazacyclopentane-1,3-diyl radical cations 3(*)(+)() were generated from Urazole-bridged bicyclic housanes 3 through chemical oxidation by using tris(4-bromophenyl)aminium hexachloroantimonate as oxidant to afford the two olefinic products 4 and 5. Product studies establish that the bisolefins 5 are the result of double oxidation of the housanes 3, whereas the monoolefins 4 are formed by acid-catalyzed rearrangement, which can be suppressed by excess of base (2,6-di-tert-butylpyridine). In the case of dibenzyl substitution (3c), disproportionation of two monoradical species 5(H)c(*) serves as an alternative pathway to the corresponding olefins 4 and 5 because higher amounts of double oxidation product were isolated in the absence of base than expected if only a stoichiometric reaction were operating. Semiempirical MO calculations suggest that ionization takes place from one of the nitrogen lone pairs rather than from the strained central C-C bond as implied by the significantly lower (by ca. 0.5 eV) ionization potential. Furthermore, in the initially puckered radical cation, the positive charge is mainly located at the two nitrogen atoms, while after relaxation to the planar geometry, the charge shifts essentially entirely to the radical cation carbon atoms. The trapping reaction with methanol leads to the hemiaminal-type products 6 and 7, which establish the involvement of the cationic intermediates 3(H)(+)() and 5(H)(+)(). In addition, (13)C NMR spectroscopy confirmed these cationic intermediates [3(H)(+)() and 5(H)(+)()] by detection of the characteristic signals below delta 250 for carbenium ions. Unquestionably, the Urazole ring significantly influences the radical cation reactivity of the housanes 3. Thus, in contrast to the corresponding homocyclic tricyclooctane derivatives, stoichiometric instead of catalytic amounts of CET oxidant are needed, the two nitrogen atoms of the hydrazino bridge stabilize the radical cation 3(*)(+)() by conjugation, and the carbonyl groups of the Urazole moiety assist the deprotonation to the exocyclic double bonds to prevent 1,2 alkyl migration.

  • generation of 4 5 diazacyclopentane 1 3 diyl radical cations by chemical electron transfer cet oxidation of Urazole bridged bicyclic housanes bicyclo 2 1 0 pentanes and their chemical transformations
    Journal of Organic Chemistry, 1996
    Co-Authors: Waldemar Adam, Thomas Kammel
    Abstract:

    4,5-Diazacyclopentane-1,3-diyl radical cations 3•+ were generated from Urazole-bridged bicyclic housanes 3 through chemical oxidation by using tris(4-bromophenyl)aminium hexachloroantimonate as oxidant to afford the two olefinic products 4 and 5. Product studies establish that the bisolefins 5 are the result of double oxidation of the housanes 3, whereas the monoolefins 4 are formed by acid-catalyzed rearrangement, which can be suppressed by excess of base (2,6-di-tert-butylpyridine). In the case of dibenzyl substitution (3c), disproportionation of two monoradical species 5(H)c• serves as an alternative pathway to the corresponding olefins 4 and 5 because higher amounts of double oxidation product were isolated in the absence of base than expected if only a stoichiometric reaction were operating. Semiempirical MO calculations suggest that ionization takes place from one of the nitrogen lone pairs rather than from the strained central C−C bond as implied by the significantly lower (by ca. 0.5 eV) ionizatio...

Shadpour Mallakpour - One of the best experts on this subject based on the ideXlab platform.

Zahra Rafiee - One of the best experts on this subject based on the ideXlab platform.

  • synthesis and characterization of poly amide ester s containing naphthalene pendent groups and Urazole rings
    Designed Monomers and Polymers, 2008
    Co-Authors: Shadpour Mallakpour, Zahra Rafiee
    Abstract:

    4-(3-Hydroxy-naphthalene)-1,2,4-triazolidine-3,5-dione (3HNTD) was synthesized in six steps starting from 3-hydroxy-2-naphthalene carboxylic acid. The reaction of monomer 3HNTD with acetyl chloride was performed in N,N-dimethylacetamide (DMAc) solution at different molar ratios, and the resulting mono-, di- and trisubstituted derivatives were obtained in high yields and were finally used as models for polymerization reactions. A series of novel aliphatic–aromatic poly(amide-ester)s (PAE)s containing a naphthalene pendent moiety were prepared from 3HNTD and various diacid chlorides (including succinyl chloride, adipoyl chloride and sebacoyl chloride) by polycondensation reactions with three methods: low-temperature solution polycondensation, solution polymerization under gradual heating and reflux conditions in the presence of pyridine and triethylamine as a proton scavenger and without a proton scavenger, respectively. PAEs from aliphatic diacid chlorides and 3HNTD have been studied in great detail via th...

  • Solid-State Polymerization of 4-(4-Dimethylaminophenyl)-Urazole with Diisocyanates
    Polymer Bulletin, 2008
    Co-Authors: Shadpour Mallakpour, Zahra Rafiee
    Abstract:

    In the present study, the solid-state thermal polymerization of 4-(4-dimethylaminophenyl)-1,2,4-triazolidine-3,5-dione (DAPTD) with diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate and toluylene-2,4-diisocyanate as a new method for synthesis of polyureas are described. The influence of reaction parameters, such as presence of catalyst in the starting material and ratio of DAPTD to diisocyanate were investigated. Polycondensation was successfully preceded without any solvent, which is used in conventional method. The resulting polyureas were obtained in high yields with inherent viscosities ranging from 0.14 to 0.25 dL/g. This method was also compared with two other polycondensation methods for the polymerization reactions which were reported before: conventional solution method and a method using tetrabutylammonium bromide as a molten ionic liquid media.

  • efficient combination of ionic liquids and microwave irradiation as a green protocol for polycondensation of 4 3 hydroxynaphthalene 1 2 4 triazolidine 3 5 dione with diisocyanates
    Polymer, 2007
    Co-Authors: Shadpour Mallakpour, Zahra Rafiee
    Abstract:

    Abstract In this investigation, a novel Urazole containing 3-hydroxynaphthalene group, 4-(3-hydroxynaphthalene)-1,2,4-triazolidine-3,5-dione (3HNTD) was synthesized in six steps starting from 3-hydroxy-2-naphthalene carboxylic acid. The reaction of 3HNTD with n-propylisocyanate was performed in N,N-dimethylacetamide solution at different molar ratios, and the resulting monosubstituted as well as disubstituted urea derivatives were obtained in high yields and were used as model compounds for polymerization studies. An efficient, fast and easy method for the preparation of new soluble poly(urea-urethane)s (PUU)s containing heterocyclic and chromophoric moieties from 3HNTD and various diisocyanates are employed using room temperature ionic liquids and molten tetrabutylammonium bromide under microwave irradiation as well as conventional heating. The polymerization reactions occurred rapidly under microwave and produced a series of PUUs with good yields and moderate inherent viscosities of 0.21–0.46 dL/g. All of the new PUUs showed good solubility and were readily dissolved in organic solvents.

  • preparation and characterization of new photoactive polyamides containing 4 4 dimethylaminophenyl Urazole units
    Journal of Applied Polymer Science, 2007
    Co-Authors: Shadpour Mallakpour, Zahra Rafiee
    Abstract:

    4-(4-dimethylaminophenyl)-1,2,4-triazolidine-3,5-dione (DAPTD) was prepared from 4-dimethylaminobenzoic acid in five steps. The compound DAPTD was reacted with excess acetyl chloride in N,N-dimethylacetamide (DMAc) solution and gave 1,2-bisacetyl-4-[4-(dimethylaminophenyl)]-1,2,4-triazolidine-3,5-dione as a model compound. Solution polycondensation reactions of monomer with succinyl chloride (SucC), suberoyl chloride (SubC), and sebacoyl chloride (SebC) were performed under conventional solution polymerization techniques in the presence of triethylamine and pyridine as a catalyst in N-methylpyrrolidone (NMP) and led to the formation of novel aliphatic polyamides. These novel polyamides have inherent viscosities in the range of 0.09–0.21 dL/g in N,N-dimethylformamide (DMF) at 25°C. Fluorimetric studies of the model compound as well as polymers were performed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 947–954, 2007

  • a simple and rapid spectrophotometric method for determination of ultra trace amounts of thallium iii with 4 4 n n dimethylaminophenyl Urazole as a new reagent
    Annali Di Chimica, 2005
    Co-Authors: Behzad Rezaei, Shadpour Mallakpour, Honieh Khalili, Zahra Rafiee
    Abstract:

    A simple and selective spectrophotometric method is proposed for the determination of ultra trace amounts of Tl(III). The reported method is based on the oxidation of 4-(4'-N,N-dimethylaminophenyl)Urazole (DAPU) to the corresponding triazolinedione (TAD) by Tl(III) at pH 4.0. The reaction was monitored spectrophotometrically by measuring the increasing color of TAD compound at 514 nm by the fixed-time method. At a given time of 2.0 min at 30 degrees C, the working range of calibration was 5.0 x 10(-8) - 2.0 x 10(-5) M Tl(III) and detection limit of 5.0 x 10(-8) M was obtained. The influences of pH, reagent concentration, ionic strength and temperature were studied. The effect of diverse ions on the determination of Tl(III) by the proposed method was also investigated. Thallium in real samples was determined by this method, with satisfactory results.

Gary W. Breton - One of the best experts on this subject based on the ideXlab platform.

  • unanticipated formation of a novel octaazacyclodecane ring upon oxidation of a 1 1 bis Urazole
    Acta Crystallographica Section C-crystal Structure Communications, 2018
    Co-Authors: Gary W. Breton, Kenneth L Martin
    Abstract:

    Tetra­hydro­tetra­zoles are a little-explored class of five-membered heterocycles with four contiguous singly-bonded N atoms. Recent work in our labs has demonstrated that Urazole radicals are amenable to N—N bond formation via radical combination to form such a chain of four N atoms. Previously described 1,1-bis-Urazole compounds appeared to be convenient precursors to the target tetra­zoles via their oxidation to inter­mediate Urazole diradicals, which upon N—N bond formation would complete the tetra­zole framework. While oxidation proceeded smoothly, the novel 10-membered octa­aza heterocycle 7,7,18,18-tetra­acetyl-4,10,15,21-tetra­phenyl-1,2,4,6,8,10,12,13,15,17,19,21-do­deca­aza­penta­cyclo­[17.3.0.02,6.08,12.013,17]docosan-3,5,9,11,14,16,20,22-octone, C42H32N12O12, was obtained (36% yield) instead of the expected tetra­zole product, as confirmed by X-ray crystallography. Calculations at the (U)B3LYP/6-311G(d,p) level of theory suggest that the desired tetra­zoles have weak N—N bonds connecting the two Urazole units.

  • intermediacy of a persistent Urazole radical and an electrophilic diazenium species in the acid catalyzed reaction of metad with anisole
    Journal of Organic Chemistry, 2016
    Co-Authors: Gary W. Breton, Alice H. Suroviec
    Abstract:

    The reaction of N-methyl-1,2,4-triazoline-3,5-dione (MeTAD) with anisole in the presence of trifluoroacetic acid affords unexpected disubstituted Urazole products instead of the expected monosubstituted Urazole as typically observed in the reactions of MeTAD with other substituted benzenes. Our investigation into the mechanism of formation of these disubstituted products suggests that MeTAD is capable of further reaction with the initially formed monosubstituted Urazole to afford a persistent Urazole radical. The identity of this radical has been established by UV–vis spectroscopy, the nature of its self-dimerization reaction, and via independent generation. Electrochemical oxidation of this radical was carried out, and the resulting diazenium ion was demonstrated to be reactive with added substituted benzenes, including anisole. When oxidation was carried out chemically using thianthrenium perchlorate in the presence of anisole it was shown to produce the same disubstituted products (and in the same rati...

  • Intermediacy of a Persistent Urazole Radical and an Electrophilic Diazenium Species in the Acid-Catalyzed Reaction of MeTAD with Anisole
    2016
    Co-Authors: Gary W. Breton, Alice H. Suroviec
    Abstract:

    The reaction of N-methyl-1,2,4-triazoline-3,5-dione (MeTAD) with anisole in the presence of trifluoroacetic acid affords unexpected disubstituted Urazole products instead of the expected monosubstituted Urazole as typically observed in the reactions of MeTAD with other substituted benzenes. Our investigation into the mechanism of formation of these disubstituted products suggests that MeTAD is capable of further reaction with the initially formed monosubstituted Urazole to afford a persistent Urazole radical. The identity of this radical has been established by UV–vis spectroscopy, the nature of its self-dimerization reaction, and via independent generation. Electrochemical oxidation of this radical was carried out, and the resulting diazenium ion was demonstrated to be reactive with added substituted benzenes, including anisole. When oxidation was carried out chemically using thianthrenium perchlorate in the presence of anisole it was shown to produce the same disubstituted products (and in the same ratio) as observed in the acid-catalyzed reaction. A common diazenium species is proposed to be active in both cases. We also report the synthesis and characterization of three interesting tetrazane dimers resulting from unstable Urazole radicals

  • alternative synthetic routes to n methyl 1 2 4 triazoline 3 5 dione metad and other triazolinedione derivatives
    Tetrahedron Letters, 2014
    Co-Authors: Gary W. Breton, Mark Turlington
    Abstract:

    Abstract N -Methyl-1,2,4-triazoline-3,5-dione (MeTAD) is a powerful electrophile and a versatile synthetic reagent. In this Letter we describe two methods for the synthesis of N -methylUrazole, the direct precursor to MeTAD, on gram scales and in good yields. Both methods provide pure Urazole while avoiding the necessity of large scale purification via column chromatography or recrystallization. One of the methods proved to be amenable for the synthesis of derivatives other than N -methyl.

  • application of radical cation spin density maps toward the prediction of photochemical reactivity between n methyl 1 2 4 triazoline 3 5 dione and substituted benzenes
    Journal of Organic Chemistry, 2013
    Co-Authors: Gary W. Breton, Kevin R Hoke
    Abstract:

    Visible light irradiation of N-methyl-1,2,4-triazoline-3,5-dione in the presence of substituted benzenes is capable of inducing substitution reactions where no reaction takes place thermally. In addition to the formation of 1-arylUrazole products resulting from ring substitution, side-chain substitution occurs in some cases where benzylic hydrogens are accessible to form benzylic Urazole products. Formation of both types of products is most consistent with the involvement of a common intermediate, a radical ion pair, generated from photoexcitation of an initially formed charge-transfer complex. The charge-transfer complexes have been observed spectroscopically. Additionally, application of a modified Rehm–Weller model suggests that the electron-transfer processes are feasible for all of the substrates examined. In most cases, the spin density maps of the aromatic radical cation intermediates calculated at the DFT UB3LYP/6-31G* level are excellent predictors of the observed product distributions.

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