- Dual roles of a xanthate as a radical source and chain transfer agent in the photoinitiated RAFT polymerization of vinyl acetate
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A high level of control over the photoinitiated RAFT polymerization of vinyl acetate (VAc) was achieved using a specifically designed xanthate, S-2-cyano-2-propyl-O-ethyl xanthate (CPEC), which acted as a radical source and a chain transfer agent simultaneously. Unlike other RAFT processes, the present system did not use any additional radical initiator, while achieving greater control over the polymerization than the photoiniferter process. The molecular weight of the resulting polymer could be modulated by changing the initial [VAc]0/[CPEC]0 ratio, but the control over the polymerization was lost with a very low initial [VAc]0/[CPEC] 0 ratio. The intensity of UV irradiation affected the polymerization by reducing the induction period and increasing the rate of polymerization but did not affect the molecular weight of the resulting polymer.
- Khan, Mohd Yusuf,Cho, Min-Soo,Kwark, Young-Je
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- Spectroelectrochemistry of potassium ethylxanthate, bis(ethylxanthato)nickel(II) and tetraethylammonium tris(ethylxanthato)-nickelate(II)
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Electrochemical and chemical oxidation of S2COEt-, Ni(S2COEt)2, and [Ni(S2COEt)3]- have been studied by CV and in situ UV-VIS spectroscopy in acetonitrile. Cyclic voltammograms of S2COEt- and Ni(S2COEt)2 display one (0.00 V) and two (0.35 and 0.80 V) irreversible oxidation peaks, respectively, referenced to an Ag/Ag+ (0.10 M) electrode. However, the cyclic voltammogram of [Ni(S2COEt)3]- displays one reversible (-0.15 V) and two irreversible (0.35, 0.80 V) oxidation peaks, referenced to an Ag/Ag+ electrode. The low temperature EPR spectrum of the oxidatively electrolyzed solution of (NEt4)[Ni(S2COEt)3] indicates the presence of [NiIII(S2COEt)3], which disproportionates to Ni(S2COEt)2, and the dimer of the oxidized ethylxanthate ligand, (S2COEt)2 ((S2COEt)2 = C2H5OC(S)SS(S)COC2H5), with a second order rate law. The final products of constant potential electrolysis at the first oxidation peak potentials of S2COEt-, Ni(S2COEt)2, and [Ni(S2COEt)3]- are (S2COEt)2; Ni2+(sol) and (S2COEt)2; and Ni(S2COEt)2 and (S2COEt)2, respectively. The chemical oxidation of S2COEt- to (S2COEt)2, and [Ni(S2COEt)3]- to (S2COEt)2 and Ni(S2COEt)2 were also achieved with iodine. The oxidized ligand in the dimer form can be reduced to S2COEt- with CN- in solution.
- Dag, Oemer,Yaman, Seniz Oezalp,Oenal, Ahmet M.,Isci, Huseyin
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- Poly(ethylene glycol)-block-poly(N-vinylformamide) copolymers synthesized by the RAFT methodology
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The radical polymerization of N-vinylformamide was followed and found to proceed in a controlled manner if an appropriate RAFT agent is employed. Use of a poly(ethylene glycol) macro-RAFT agent allowed for the generation of block copolymers of PEG and PNVF.
- Shi, Lianjun,Chapman, Toby M.,Beckman, Eric J.
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- Thiol-end-functionalized polyethylenes
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Synthesis of well-defined and highly thiol-end-functionalized polyethylene (PE-SH) was performed using olefin polymerization by coordination chemistry and robust functionalization chemistries. Using a Nd-based catalyst in combination with n-butyloctylmagnesium (BOMg), dipolyethylenylmagnesium compounds (PE-Mg-PE) were first prepared by catalyzed polyethylene chain growth on magnesium. Taking advantage of the reactivity of the carbon-magnesium bonds so formed, several functionalization strategies were assessed with the main aim of producing the targeted PE-SH in the simplest and most efficient way. In particular, polysulfurs and thiothiocarbonylated-end-functionalized polyethylenes were successfully obtained and reduced by lithium aluminum hydride (LiAlH 4) to give the desired PE with up to 90% thiol chain end functionality.
- Mazzolini, Jerome,Mokthari, Ilham,Briquel, Remi,Boyron, Olivier,Delolme, Frederic,Monteil, Vincent,Bertin, Denis,Gigmes, Didier,D'Agosto, Franck,Boisson, Christophe
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- Activating ATRP Initiators to Incorporate End-Group Modularity into Photo-RAFT Polymerization
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Heterogeneous photocatalysis is increasingly used in reversible deactivation radical polymerization (RDRP). In this study, we found that alkyl bromide redox chemistry typically found in atom transfer radical polymerization (ATRP) can be incorporated in concert with dithiocarbonyl disulfide chemistry into the reversible addition-fragmentation chain transfer (RAFT) process via bismuth oxide photocatalysis. This amalgamation of mechanisms introduces end-group modularity - a new layer of control - into RAFT polymers uniquely enabled by photoredox catalysis. We found that a diversity of functionality can be installed at the α-end group via alkyl bromides, while the molecular weight distribution can be tuned seamlessly at the ω-end group through the simultaneous addition of multiple disulfides.
- Hakobyan, Karen,McErlean, Christopher S. P.,Müllner, Markus
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p. 10357 - 10365
(2020/12/23)
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- NH4I/EtOCS2K promoted synthesis of substituted benzils from diphenylacetylene derivatives
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A facile protocol is described for the synthesis of benzil derivatives from readily accessible diarylacetylene derivatives using the NH4I/EtOCS2K system. This novel protocol results in excellent chemoselectivity and provided good to excellent yields. A control experiment indicated that the reaction proceeds via NH4I promoted EtOCS2K dimerization to give the corresponding dixanthogen and subsequent dixanthogen assisted oxidation.
- Jiang, Shaohua,Li, Yibiao,Luo, Xianglin,Huang, Guoling,Shao, Yan,Li, Dongli,Li, Bin
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supporting information
p. 3249 - 3252
(2018/07/21)
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- Coupling of gem-difluorinated organozinc reagents with S-electrophiles
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gem-Difluorinated organozinc reagents, which were prepared by insertion of CF2-fragment into C[sbnd]Zn bond, couple with diethyl dixanthogen, di(benzothiazolyl) disulfide, and tetraethylthiuram disulfide. The reaction is promoted either by a copper(I) catalyst or by irradiation with blue light in the presence of Eosin Y disodium salt.
- Ashirbaev, Salavat S.,Levin, Vitalij V.,Struchkova, Marina I.,Dilman, Alexander D.
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p. 143 - 148
(2016/10/24)
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- Photochemistry of S -phenacyl xanthates
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Various synthetically readily accessible S-phenacyl xanthates are shown to undergo photoinitiated homolytic scission of the C-S bond in the primary step. The resultant fragments, phenacyl and xanthic acid radicals, recombine to form symmetrical 1,4-diketones and xanthogen disulfides, respectively, in high to moderate chemical yields in chemically inert solvents. They can also be efficiently trapped by a hydrogen-atom-donating solvent to give acetophenone and xanthic acid derivatives. The latter compound is in situ thermally converted to the corresponding alcohol in high chemical yields. S-Phenacyl xanthates could thus be utilized as synthetic precursors to the above-mentioned compounds or as photoremovable protecting groups for alcohols in which the xanthate moiety represents a photolabile linker. The photochemically released phenacyl radical fragments efficiently but reversibly add to the thiocarbonyl group of the parent xanthate molecule. The kinetics of this degenerative reversible addition-fragmentation transfer (RAFT)/macromolecular design via the interchange of xanthates (MADIX) mechanism was studied using laser flash photolysis (LFP) and density functional theory (DFT) calculations. The rate constants of the RAFT addition step, kadd ~ 7 × 108 M-1 s-1, and phenacyl radical addition to a double bond of 1,1-diphenylethylene, kadd ~ 108 M-1 s -1, in acetonitrile were experimentally determined by LFP. In addition, photoinitiation of the methyl methacrylate polymerization by S-phenacyl xanthate is demonstrated. The polydispersity index of the resulting poly(methyl methacrylate) was found to be ~1.4. We conclude that S-phenacyl xanthates can serve simultaneously as photoinitiators as well as RAFT/MADIX agents in polymerization reactions.
- Tazhe Veetil, Aneesh,Solomek, Tomas,Ngoy, Bokolombe Pitchou,Pavlikova, Nela,Heger, Dominik,Klan, Petr
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experimental part
p. 8232 - 8242
(2012/01/03)
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- A synthesis of N-alkyl and N,N-dialkyl O-ethyl thiocarbamates from diethyl dixanthogenate using different oxidants
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A novel synthesis of N-alkyl and N,N-dialkyl O-ethyl thiocarbamates from diethyl dixanthogenate and primary and secondary amines, using three oxidizing systems, has been developed on the laboratory scale, and the method using sodium hypochlorite has been applied on a semi-industrial scale. The effect of the oxidizing agents, sodium hypochlorite, in-situ-generated peracetic acid, and the manganese(II) acetate/oxygen system on product purity and yield was studied. The results obtained by use of these three methods were compared with those obtained by reaction of sodium ethyl xanthogenacetate and amines, and of sodium ethyl xanthate with amines in the presence of sulfated nickel zeolite catalyst. The reaction mechanism of sodium hypochlorite oxidation has been established on the basis of isolation of reaction intermediates and determination of their structure by use of Fourier-transform infrared, 1H and 13C NMR, and mass spectrometric methods. The suggested sodium hypochlorite and manganese(II) acetate/oxygen systems have many advantages in comparison with commercial and catalytically promoted synthetic methods, because they are new ecologically friendly syntheses. Springer-Verlag 2010.
- Milosavljevic, Milutin M.,Sovrlic, Milica,Marinkovic, Aleksandar D.,Milenkovic, Dragan D.
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experimental part
p. 749 - 755
(2011/07/08)
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- Polymer-protein conjugates from ω-aldehyde endfunctional poly(N-vinylpyrrolidone) synthesised via xanthate-mediated living radical polymerisation
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Aldehyde ω-endfunctional poly(N-vinylpyrrolidone) was synthesised via quantitative conversion of a xanthate endfunctional precursor obtained via RAFT-mediated polymerisation. The Royal Society of Chemistry.
- Pound, Gwenaelle,McKenzie, Jean M.,Lange, Ronald F. M.,Klumperman, Bert
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supporting information; experimental part
p. 3193 - 3195
(2009/02/04)
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- Facile preparation of bis(thiocarbonyl)disulfides via elimination
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A robust facile synthetic preparation of bis(thiocarbonyl)disulfides is presented. The route follows an elimination mechanism rather than the more common oxidation. Addition of p-tosyl chloride to a thiocarbonyl thiolate results in the elimination of the chloride by the trithiocarbonate anion and subsequent elimination of the tosyl leaving group (by a second thiocarbonyl thiolate). The side products of the reaction are bis(4-methylphenyl)disulfone and tosylate salts/acids.
- Weber, Wolfgang G.,McLeary, James B.,Sanderson, Ron D.
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p. 4771 - 4774
(2007/10/03)
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- Spectroscopic characterization of ethyl xanthate oxidation products and analysis by ion interaction chromatography
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An ion interaction chromatographic separation method, coupled with UV spectroscopic detection, has been developed for the analysis of ethyl xanthate (O-ethyl dithiocarbonate) and its oxidative decomposition products in mineral flotation systems. The effects of the ion-pairing agent (tetrabutylammonium ion), pH modifier (phosphoric acid), and organic modifier (acetonitrile) in the eluant upon the retention characteristics of the ethyl xanthate oxidation products have been determined. The optimized separation procedure has been successfully applied to the analysis of ethyl xanthate and its oxidation products in a nickel-iron sulfide mineral suspension containing a number of other anionic species, including cyanide complexes of nickel and iron, as well as sulfur-oxy anions. The ethyl xanthate oxidation products investigated in this study have been isolated as pure compounds and characterized by UV-visible, FT-IR, and NMR spectroscopies. The UV-visible and FT-IR spectroscopic properties of these species are discussed in terms of the chemical modifications of the thiocarbonate group.
- Hao, Fu Ping,Silvester, Ewen,Senior, Geoffrey David
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p. 4836 - 4845
(2007/10/03)
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- Synthesis of dimer phosphoramidite synthons for oligodeoxyribonucleotide phosphorothioates using diethyldithiocarbonate disulfide as an efficient sulfurizing reagent
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An efficient solution phase synthesis of deoxyribonucleoside phosphorothioate dimers utilizing phosphoramidite approach is described. Diethyldithiocarbonate disulfide (DDD) was found to be an efficient sulfurizing reagent in the conversion of phosphite triesters to phosphorothioate triesters.
- Eleuteri, Alessandra,Cheruvallath, Zacharia S.,Capaldi, Daniel C.,Cole, Douglas L.,Ravikumar, Vasulinga T.
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p. 1803 - 1807
(2007/10/03)
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- A novel synthesis of functional dithioesters, dithiocarbamates, xanthates and trithiocarbonates
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A novel synthesis of functional dithioesters, dithiocarbamates, xanthates and trithiocarbonates is described. Heating a bis(thiocarbonyl) disulfide with an azo-compound results in the formation of (thiocarbonyl)sulfanyl derivatives in moderate to high yield. The process is proposed as the method of choice for preparing tertiary (thiocarbonyl)sulfanyl compounds and is compatible with a wide range of functionalities (e.g. carboxy, hydroxy and nitrile).
- Thang, San H.,Chong, Bill Y.K.,Mayadunne, Roshan T.A.,Moad, Graeme,Rizzardo, Ezio
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p. 2435 - 2438
(2007/10/03)
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- The Reaction of Triphenylmethyl Bromide with Potassium O-Ethyl Dithiocarbonate (Potassium Xanthate) in Benzene and Cumene. A Note of Caution on the Application of the Radical Trap Dicyclohexylphosphine as a Probe for Electron-transfer-initiated Reactions of Triphenylmethyl Halides
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The title reaction was studied under conditions where homolysis of the triphenylmethyl-to-sulphur bond of the dithiocarbonate 1d, its main product does not take place, or is negligible.Triphenylmethane 1c, triphenylmethanol 1g and benzophenone were obtained as further products under argon in cumene and in the presence of oxygen in benzene, respectively.This, together with ESR studies, indicates that part of the dithiocarbonate 1d results from single-electron transfer from O-ethyl dithiocarbonate anion to triphenylmethyl bromide 1a and out-of-cage recombination of triphenylmethyl and xanthyl radicals 6a.The main pathways leading to dithiocarbonate 1d appear, under the conditions studied, to be either a polar pathway consisting of two successive SN2'-type steps and/or an SET-type reaction with rapid in-cage recombination of triphenylmethyl and xanthyl radicals 6a.The hydrogen-atom donor dicyclohexylphosphine (DCPH) may not be used for trapping of the triphenyl radicals formed in the title reaction because DCPH acts as a single-electron donor towards bromide 1a, i.e. it itself generates triphenylmethyl radicals from the bromide.
- Huszthy, Peter,Izso, Gyoengyi,Lempert, Karoly,Gyoer, Miklos,Rockenbauer, Antal
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p. 2009 - 2015
(2007/10/02)
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- The Oxidation of Dithiocarbamate Anion by Substitution Inert Metal Complexes
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The kinetics of oxidation of dithiocarbamate anions to thiuram disulfides in aqueous acetone by 3- and 11 other substitution inert metal complexes have been investigated.Outer-sphere electron transfer, resulting in the formation of dithiocarbamate thio radicals, is the rate determining step.A Marcus cross reaction treatment allows an estimate for the redox potential for the dithiocarbamate radical/anion couple.For diethyldithiocarbamate, Edeg(edtc./edtc-) = 425+/-33 mV ν.s.c.e. and the outer-sphere electron self-exchange rate constant is logkex = 7.0+/-0.3.A comparison with thiophenolate oxidation is also given.
- Nichols, Peter J.,Grant, Michael W.
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p. 1085 - 1102
(2007/10/02)
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- Photochemical and Thermal Transformations of O-Alkyl-S-phthalylalanyl Xanthates
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The reaction of phthalylalanyl chloride with different potassium O-alkylxanthates (R = Et, n-pr, iso-pr, n-Bu, iso-Bu) around 0 deg C in ether solution gave rise to the corresponding O-alkyl-S-phthalylalanyl xanthates.Irradiation of the latter in benzene solution gave xanthic acid disulphide, phthalylalanine and thioanhydride of phthalylalanine in addition to some other products.Thermal decomposition of these acylxanthates around 150 - 60 deg C for 15 - 20 min yielded the corresponding esters and carbon disulphide.
- Darji, R. R.,Shah, A.
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p. 104 - 106
(2007/10/02)
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- Redox Reactions in Non-aqueous Media. Determination of Xanthates and Organotrithiocarbonates (Thioxanthates) with Iron(III) in Acetonitrile
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The use of iron(III) perchlorate (in acetonitrile) for the visual, potentiometric and spectrophotometric determination of xanthates and organotrithiocarbonates (thioxanthates) in acetonitrile medium is described.The proposed methods are simple, accurate and reliable and show the promise of wide applicability.
- Verma, B. C.,Sharma, Neelam,Sud, Anila,Sharma, Usha,Sud, Anita
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p. 625 - 626
(2007/10/02)
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- Bromonitromethane. A Versatile Electrophile
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Pathways in reactions of bromonitromethane with a variety of nucleophiles have been investigated.With thiolates, the electrophilic centre is bromine and the initial products are disulphides.When the thiolate ion itself carries an electrophilic centre such as carbonyl or cyano β-to sulphur, the product is a nitrothiophene derived from subsequent reaction of the first-formed disulphide with nitronate ion displaced in the initial process.This provides a generalisation of earlier nitrothiophene synthesis by this route.In reactions with arenesulphinate ion, the electrophilic centre is also bromine and equilibration between the initial reactants and the initial products, sulphonyl bromide and nitronate ion, is established.The components of the equilibrium subsequently react either with each other or with the solvent.Reactions with sulphides are slow and distal substituents such as hydroxy- or cyano- so much reduce reactivity that no reaction is observed.Dimethyl sulfide attacks bromonitromethane at the carbon atom,and subsequent attack on the nitromethyl sulphonium salt initially formed gives methylthionitromethane and trimethylsulphonium bromide.Iodide ion attacks at bromine to give iodine, presumably via iodine bromide, but with tervalent phosphorus nucleophiles, attack is at oxygen giving the corresponding oxides and HCN in a double deoxygenation sequence.For hydroxide, methoxide and hydride ions (from sodium borohydride), nucleophilic attack is at hydrogen and the nitronate ion produced is inert to further attack.There is no evidence of carbene formation by α-elimination.When the anion of bromonitromethane is allowed to react with tributylboron, the anionic migration-displacement which follows boron-carbon bond formation, yields 1-nitropentane.The anion of bromonitromethane is unreactive towards aldehydes and electrophilic alkenes.
- Fishwick, Brian R.,Rowles, David K.,Stirling, Charles J. M.
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p. 1171 - 1180
(2007/10/02)
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- Novel Symmetrical and Mixed Carbamoyl and Amino Polysulfanes by Reactions of (Alkoxydichloromethyl)polysulfanyl Substrates with N-Methylaniline
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Reactions of (alkoxydichloromethyl)polysulfanes with N-methylaniline can be rationalized by a "carbamoyl" route where the alkoxydichloromethyl group behaves via loss of alkyl chloride as a "masked" acid chloride or by a "sulfenyl" route which reflects fragmentation of the (alkoxydichloromethyl)polysulfanyl functionality into the corresponding alkoxy(thiocarbonyl) and sulfenyl components (cf.Scheme I).Application of this and related chemistry to bifunctional substrates arising from partial or complete chlorination of 2Sm, R = Me, Et, i-Pr, and m = 1-4, has led to Ph(Me)N(C=O)Sn(C=O)N(Me)Ph, n = 2-12; Ph(Me)N(C=O)SnN(Me)Ph, n = 1-6; Ph(Me)NSnN(Me)Ph, n = 1-10; RO(C=S)Sn(C=O)N(Me)Ph, n = 2, 3; and RO(C=S)SnN(Me)Ph, n = 1-5.These families allowed a test of reversed-phase high-pressure liquid chromatography for evaluating homologies in polysulfane series.Treatment of bis sulfide (27c) with sulfuryl chloride in the presence of calcium carbonate conveniently gave distillable bis(chlorocarbonyl)trisulfane (14), whereas the same procedure with SO2Cl2 alone gave directly (chlorocarbonyl)disulfanyl chloride (12) (see Scheme VII).Higher Cl(C=O)SmCl, m = 3-5, were indicated but could not be isolated in the course of studies generalizing results on 14 to the preparation of higher Cl(C=O)Sn(C=O)Cl, n = 4-6.The new bis(carbamoyl) monosulfide 61 was obtained by the relatively slow triphenylphosphine or cyanide promoted desulfurization of bis(methylphenylcarbamoyl)disulfane (4) (eq. 1 and 4); cyanide treatment of the higher polysulfanes Ph(Me)N(C=O)Sn(C=O)N(Me)Ph for n > 3 rapidly gave disulfane directly (eq 5).
- Schroll, Alayne L.,Barany, George
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p. 1866 - 1881
(2007/10/02)
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- A General Strategy for Elaboration of the Dithiocarbonyl Functionality, -(C=O)SS-: Application to the Synthesis of Bis(chlorocarbonyl)disulfane and Related Derivatives of Thiocarbonic Acids
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A variety of sulfenyl chlorides have been reacted with a variety of alkoxythiocarbonyl compounds to give adducts which then lose (spontaneously, or upon thermolysis, or in the presence of Lewis acid catalyst) the alkyl chloride to provide an assortment of dithiocarbonyl compounds in good to excellent yields.The preparations of bis(chlorocarbonyl)disulfane (1), ((trichloromethyl)dithio)carbonyl chloride (2), ((alkoxycarbonyl)dithio)carbonyl chlorides (3 and 4), and (((alkylthio)carbonyl)dithio)carbonyl chlorides (5 and 6) by this methodology were optimized; some of the (alkoxydichloromethyl)disulfanyl adducts, e.g., ROCCl2SS(C=O)Cl (10) and ROCCl2SS(C=O)OR'(54), were reasonable stable and could be isolated.All new compounds were characterized by analytical data, 1H and 13C NMR, IR, UV, and mass spectrometry, and high-yield derivatizations with alcohols or N-methylaniline.The reaction with N-methylaniline was also adapted to a rapid, convenient, and precise analytical-scale assay of mixtures of compounds containing acid chloride and/or sulfenyl chloride functionalities.The kinetics, mechanism, and stereochemistry of the dithiocarbonyl synthesis are discussed.
- Barany, George,Schroll, Alayne L.,Mott, Andrew W.,Halsrud, David A.
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p. 4750 - 4761
(2007/10/02)
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- Reduction Potentials of Thiuram Disulfide/Dithiocarbamate Couples in Acetone/Water
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Reduction potentials relative to the saturated calomel electrode, Eo, of a series of thiuram disulfide/dithiocarbamate couples have been measured in 30percent v/v water in acetone and at μ 0.2 mol l-1 (NaNO3) by a combination of potentiometric measurements and equilibrium constant determinations for thiolate/disulfide interchange reactions.Eo values lie in the range -250 to -340 mV which place dithiocarbamates as intermediate between thiophenolate (Eo -540 mV) and ethylxanthate (Eo -206 mV) in reducing properties.The significant effect on Eo of varying the substituents on the nitrogen in the dithiocarbamates correlates with the substituent effects on the acid dissociation constants of the parent dithiocarbamic acid and with trends in the half-wave potentials for metal-based oxidation and reduction of transition metal dithiocarbamate complexes.
- Nichols, Peter J.,Grant, Michael W.
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p. 2455 - 2463
(2007/10/02)
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- Reactions of Toluene-p-sulphonic Thioanhydride with Sulphur Nucleophiles
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Ethoxythiocarbonyl p-tolylsulphonyl disulphide (5), benzylthio(thiocarbonyl) p-tolylsulphonyl disulphide (1c), and NN-dimethylthiocarbamoyl p-tolylsulphonyl disulphide (10) are formed in the reactions of toluene-p-sulphonic thioanhydride (3) with O-ethyl dithiocarbonate (4), benzyl trithiocarbonate (2), and NN-dimethyl dithiocarbamate (9) ions, respectively.
- Hansen, Holger C.,Senning, Alexander
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p. 692 - 693
(2007/10/02)
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