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The reactivity of the prototypical phosphorus-containing ylidion (α-distonic ion) ·CH2PH3+ has been investigated in the gas phase by using a dual cell Fourier-transform ion cyclotron resonance mass spectrometer. The ion ·CH2PH3+ and its more stable conventional isomer CH3PH2·+ show distinctly different reactivities toward neutral reagents. This observation contrasts the facile interconversion of the analogous sulfur- and oxygen-containing distonic ions ·CH2SH2+ and ·CH2OH2+ with their conventional isomers CH3OH·+ and CH3SH·+, respectively, within collision complexes in the gas phase. Bracketing experiments yield a proton affinity of 190.4 ± 3 kcal mol-1 for the phosphorus atom in ·CH2PH2. Together with a calculated heat of formation for ·CH2PH2, this value yields a heat of formation of 217 ± 3 kcal mol-1 (at 298 K) for the distonic ion ·CH2PH3+.

UV and IR absorption cross sections were measured for methyl thionitrite at 298 K.This compound was found to undergo photochemical reactions in the wavelength region of 300-400 nm via CH3SNO + hν -> CH3S + NO followed by CH3S + NO -> CH3SNO and 2CH3S -> CH3SSCH3.Preliminary results on the mechanism of the reaction of CH3S with O2 were also obtained.

The role of amino acids and α-dicarbonyls in the flavor formation of Amadori rearrangement product (ARP) during thermal processing was investigated. Comparisons of the volatile compounds and their concentrations when N-(1-deoxy-α-D-ribulos-1-yl)-glycine r

Dimethyl sulfoxide (DMSO) is widely used in the chemical industry. However, it has a non-neglectful thermal runaway risk due to the nature of self-accelerating decomposition near the boiling point. Under the background that zinc oxide (ZnO) may extend the isothermal induction period of thermal decomposition of DMSO, this article conducts an in-depth study for the phenomenon with the techniques such as differential scanning calorimetry (DSC), accelerating rate calorimetry (ARC), gas chromatography-mass spectrometry (GC-MS), X-ray photoelectron spectroscopy (XPS), and X-ray diffractometry (XRD). After being mixed with ZnO, the maximum decomposition rate of DMSO was significantly reduced and the adiabatic induction period of DMSO decomposition was extended by 3.27 times, indicating that the thermal decomposition intensity of DMSO was obviously reduced. It was experimentally demonstrated that ZnO did not change the decomposition pathways of DMSO, but it could promote the decomposition of methanethiol, which was a decomposition intermediate of DMSO and could potentially serve as a promoter on the decomposition of DMSO.

Porous carbon spheres with high surface area and microporous structure were synthesized from alkyl phenols and formaldehyde via suspension polymerization and steam activation. The effects of air oxidation and ammonia solution heat treatment on the pore structure and surface chemistry of the carbon spheres were studied for catalytic oxidation of CH3SH. The structure property and surface chemistry of the obtained carbon spheres were characterized by N2 adsorption-desorption, FTIR, scanning electron microscopy, XRD, elemental analysis, X-ray photoelectron spectroscopy and Boehm titration, and then thermal analysis and gas chromatography-mass spectrometry were applied to investigate the catalytic oxidation product. Results show that the as-prepared microporous carbon spheres through direct ammonia treatment have a high surface area value of 1710 m2 g-1 and a total pore volume of 0.83 cm3 g-1. Moreover, the preoxidation-assisted nitrogen enrichment strategy not only increases the surface area and total pore volume of the carbon spheres, but also introduces more active nitrogen species such as pyridinic nitrogen and quaternary nitrogen, leading to the highest nitrogen content of 7.13 wt% and the highest CH3SH capacity of 622.8 mg g-1 due to the pyridinic nitrogen and quaternary nitrogen as function of catalysts. In addition, water and oxygen have a beneficial effect on CH3SH oxidation over the nitrogen modified carbon spheres, and the basic oxidation product is CH3SSCH3 that can be further oxidized into CH3SO2SCH3 according to DTG and GC/MS analysis. The great recycling stability after ten cycles with a reserved CH3SH capacity of 97% demonstrates that the porous carbon spheres obtained by preoxidation-assisted enriched nitrogen strategy are promising for catalytic oxidation of CH3SH. This journal is

Several recent studies have shown unique adsorption activity of metal organic frameworks (MOFs) towards unsaturated hydrocarbons. In the current article, we explored the application of Ni-MOFs for S-functionalization of acetylene. We showed that Ni-MOF-74 catalyzed the reaction of disulfide addition to gaseous acetylene with excellent selectivity. The prime advantage of the proposed Ni-MOF-74 over other examined catalysts was its easy separation and recycling possibility. Moreover, it demonstrated no leaching of Ni species into the solution. The work was supplemented with a study on the catalyst behavior in the course of the reaction by using SEM, EDX, XRD, and FT-IR methods.

Process concepts have been conceived and evaluated for the amine-free homogeneous catalyzed hydrogenation of CO2 to formic acid (FA). Base-free DMSO-mediated production of FA has been shown to avoid the formation of stable intermediates and presumably the energy-intensive FA recovery strategies. Here, we address the challenges in the development of an overall process: from catalyst immobilization to the FA isolation. The immobilization of the homogeneous catalyst was achieved using a multiphasic approach (n-heptane/DMSO) ensuring high retention of the catalyst (>99%) and allowing facile separation of the catalyst-free product phase. We show that the strong molecular interactions between DMSO and FA on the one hand shift the equilibrium towards the product side, on the other hand, lead to the formation of an azeotrope preventing a simple isolation step by distillation. Thus, we devised an isolation strategy based on the use of co-solvents and computed the energy demands. Acetic acid was identified as best co-solvent and its compatibility with the catalyst system was experimentally verified. Overall, the outlined process involving DMSO and acetic acid as co-solvent has a computed energy demand on a par with state-of-the art amine-based processes. However, the insufficient chemical stability of DMSO poses major limitations on processes based on this solvent. (Figure presented.).

Dicationic thiolate-bridged diruthenium complexes bearing sterically bulky alkane substituents on the thiolate ligands such as [Cp?Ru(μ-SiPr)2Ru(OH2)Cp?](OTf)2 have been found to work as effective catalysts toward oxidation of molecular dihydrogen into protons and electrons in protic solvents such as water and methanol. DFT calculations indicate that the sterically bulky alkane substituent in the complex plays an important role in facilitating the reaction step of the coordination of molecular dihydrogen.

The radical cation of cytosine (Cyt.+) is generated by dissociative oxidation from a ternary CuII complex in the gas phase. The radical cation is characterized by infrared multiple photon dissociation (IRMPD) spectroscopy in the fingerprint region, UV/Vis photodissociation (UVPD) spectroscopy, ion–molecule reactions, and theoretical calculations (density functional theory and ab initio). The experimental IRMPD spectrum features diagnostic bands for two enol-amino and two keto-amino tautomers of Cyt.+ that are calculated to be among the lowest energy isomers, in agreement with a previous study. Although the UVPD action spectrum can also be matched to a combination of the four lowest energy tautomers, the presence of a nonclassical distonic radical cation cannot be ruled out. Its formation is, however, unlikely due to the high energy of this isomer and the respective ternary CuII complex. Gas-phase ion–molecule reactions showed that Cyt.+ undergoes hydrogen-atom abstraction from 1-propanethiol, radical recombination reactions with nitric oxide, and electron transfer from dimethyl disulfide.

The invention relates to a production method for dimethyl disulfide. The production method comprises the following steps: subjecting methyl mercaptan and strong base to reaction so as to generate methanthiol salt, and subjecting methanthiol salt and oxygen-containing gas to oxidation reaction so as to prepare dimethyl disulfide. The method provided by the invention combines a caustic soda liquid absorption method and an oxidation method to realize preparation of dimethyl disulfide, and has the advantages of small explosive range, basically no by-product, high product purity, high yield, etc.

The present invention relates to a novel use of magnetic iron oxide red Fe21.333O32 as a catalyst in oxidizing methanthiol to prepare dimethyl disulfide. The magnetic iron oxide red Fe21.333O32 according to the present invention has extremely high catalytic selectivity in catalyzing and oxidizing methanthiol to prepare dimethyl disulfide. The magnetic iron oxide red Fe21.333O32 is prepared with a carbonate and a ferrite as raw materials, has advantages of low cost and simple preparation process, and is suitable for industrial production.

A method for producing dimethyl disulfide from methyl mercaptan and sulphur by employing a sulfuration process comprises the following steps: introducing methyl mercaptan and sulphur according to a molar ratio of 2:(0.95-1.55) into a reactor, in the presence of a catalyst, at a temperature of 50-550 DEG C, under a pressure of 0.05-0.5 MPa, reacting to obtain reaction products dimethyl disulfide and hydrogen sulfide, discharging hydrogen sulfide from the reactor for cyclic utilization for preparing methyl mercaptan, and performing condensation and cooling on dimethyl disulfide to obtain a crude product dimethyl disulfide, and performing rectification to obtained a qualified dimethyl disulfide finished product. The provided method for producing dimethyl disulfide from methyl mercaptan and sulphur by employing the sulfuration process is simple in production process, low in production cost, beneficial for large-scale industrialized production and less in produced ''three wastes (waste gas, waste water and industrial residue)'' discharge, and has substantial social benefic and economic benefit.

The Beckmann rearrangement of ketoximes, mediated by ammonium persulfate-dimethyl sulfoxide as a reagent, has been achieved under neutral conditions. Based on the radical trapping and 18O-labeling experiments, the transformation follows a mechanism involving a radical pathway. The scope and generality of the developed protocol has been demonstrated by 19 examples. The developed protocol and Pd-catalyzed intramolecular double C-H activation were used as key steps in the formal total synthesis of antimalarial natural product isocryptolepine.

The invention relates to a process for the preparation of symmetrical or asymmetrical dialkyl disulphides by involving at least one mixture of symmetrical and/or asymmetrical dialkyl disulphides in a basic and/or photochemical catalytic reaction, with joint extraction, preferably continuously, of the symmetrical and/or asymmetrical disulphide(s) which it is desired to obtain. The process of the invention is particularly suited to the preparation of dimethyl disulphide or diethyl disulphide from a mixture of symmetrical and/or asymmetrical dialkyl disulphides.

CuCl2 has been shown to effectively catalyze reshuffling of the inherent sulfur crosslinked networks of vulcanized rubber. Once activated, CuCl2-based complex catalysis enables disulfide metathesis through circulated crossover reactions among disulfide and polysulfide bonds without forming radicals and ionic intermediates. By taking advantage of this mechanism, the model material of this study, vulcanized polybutadiene rubber, acquires thermal remendability as characterized by repeated restoration of mechanical properties. Moreover, it can be reprocessed like thermoplastics. The compositions and fabrication of the model material simulate those of industrial vulcanized rubber, so as to facilitate formulation optimization under the circumstances close to the actual situation for possible future practical applications. It is hoped that the results of the present preliminary exploration would provide the basis for extending the service life and developing new recycling techniques of vulcanized rubber, which is produced, used and scrapped in large quantities every day.

Chiral silica (P)-nanoparticles grafted with (P)-helicene recognize the molecular structure of a chiral diol disulfide in the presence of monool disulfide and dibutyl disulfide. The (P)-nanoparticles selectively adsorb the diol disulfide, aggregate, and precipitate from solution. Under rhodium-catalyzed equilibrium among three disulfides, the diol disulfide is removed from solution by precipitation, which induces an equilibrium shift in the solution. By conducting the precipitation experiment twice, we obtained the diol disulfide in 37% yield from a statistical 1:2:1 equilibrium mixture of three disulfides. The method is applied to a racemic monool disulfide, and an optically active diol disulfide is obtained via kinetic resolution and equilibrium shift.

The gas-chromatographic retention indices of the products of 1,1-dimethylhydrazine transformations in the presence of sulfur allows one to confirm and, in ceratin cases, make more exact the results of their gas chromatography-mass spectrometry identificat

The present disclosure relates to a process for obtaining dialkyl disulphides from alkyl mercaptan and from sulphur, in which a reaction intermediate present in the final disulphide is decomposed at the end of synthesis. This operation makes it possible to avoid the degradation of said reaction intermediate over time, which is responsible for the decrease in purity of the dialkyl disulphide.

RhH(PPh3)4 and 1,2-bis(diphenylphosphino)benzene (dppBz) catalyzed the oxidative coupling reaction of aryl benzyl ketones giving 2,3-diaryl-1,4-diketones in high yields. 3,3-Dimethyl-1-methylthio-2-butanone was used as the oxidizing

An operationally simple and environmentally benign method for reductive coupling of sulfonyl chlorides to the corresponding disulfides has been developed. Sulfonyl chlorides can be rapidly reduced with SO2/KI/ H2SO4 system in moderate to good yields at 80 C in water. Graphical Abstract: [Figure not available: see fulltext.]

An efficient and odorless synthesis of disulfides from alkyl halides using thiourea and elemental sulfur in the presence of sodium carbonate in wet polyethylene glycol (PEG 200) at 40 C without contamination by higher polysulfides has been developed. This procedure was then extended to preparation of disulfides from alkyl tosylates at 70 C.

5,12-Bis(methylthio)tetracene (2) and 5,11-bis(methylthio)tetracene (3) were synthesized. DFT calculations indicate that the HOMO and LUMO energy levels of 2 and 3 are lowered by 0.13-0.24 eV and their HOMO-LUMO energy gaps are reduced by 0.1 eV relative to those of tetracene. X-ray crystallographic data revealed that 2 is arranged as a result of a 1-D slipped-cofacial π-stacking with S-S and S-π interactions, similar to the packing arrangement of 6,13-bis(methylthio)pentacene (1), whereas 3 exhibits a herringbone packing arrangement without S-S interactions. The OFET devices fabricated using spin-coated films of soluble 1 and 2, with a bottom-contact device configuration, exhibited hole mobilities as high as 1.3 × 10-2 and 4.0 × 10-2 cm2 V-1 s-1 with current on/off ratios of over 105 and 104, respectively.

Bipyridinium tribromide reacts with thiols in the presence of thionyl chloride to yield symmetric trisulfide derivatives (RSS(O)SR) as the major products. Two possible mechanisms are advanced to explain the chemistry.

A new, general method for the preparation of N,N-di-methyl-N′- arylureas using S,S-dimethyl dithiocarbonate as a phosgene substitute is reported. The method has been set up according to four procedures, all including three steps: (1) reaction of S,S-di- methyl dithiocarbonate with dimethylamine to give S-methyl N,N-dimethylthiocarbamate; (2) halogenation with various halogenating reagents (chlorine, methanesulfenyl chloride, bromine, and meth-anesulfenyl bromide) to give N,N-dimethylcarbamoyl chloride or bromide; (3) in situ reaction with primary arylamines. All the target products were obtained in high yields (85-98%; 16 reactions, average yield 93%) and with high purity. Also noteworthy is the recovery of byproducts of industrial interest, namely methanethiol and dimethyl disulfide, with complete exploitation of the reagent S,S- dimethyl dithiocarbonate. Georg Thieme Verlag Stuttgart.

A process and graded catalyst bed for selectively producing methyl mercaptan from methanol. The methanol is reacted with hydrogen sulfide, in the presence of a graded catalyst bed containing at least three types of nickel or cobalt molybdenum alumina catalysts to convert the methanol to methyl mercaptan in one-pass. At least one of the hydrotreating catalysts can contain aluminium phosphate. Use of the graded catalyst bed prevents the formation of a hot spot within the graded catalyst bed. The methyl mercaptan having less than about 30 wt. % unreacted methanol contained therein.

The Wilkinson complex RhCl(PPh3)3 catalyzes equilibrating alkylthio exchange reaction of thioesters with disulfides. The treatment of a thioester and a dialkyl disulfide in refluxing diethyl ketone in the presence of RhCl(PPh3)3 (2.5 mol %) for 1.5 h gave an alkylthio exchanged thioester. The reaction of S-methyl ester was conducted shifting the equilibrium by removing volatile dimethyl disulfide.

Methods and materials for preparing optically active 3,4-disubstituted cyclopentanones are disclosed. The method includes hydrolyzing one or more compounds represented by Formula (13), or removing an ester moiety from a compound represented by Formula (18).

Structural requirements for compounds involved in Allium discoloration have been investigated in detail. The abilities of all 20 protein amino acids and six naturally occurring 1-propenyl-containing thiosulfinates to form the pigments have been studied. Furthermore, several analogues of these thiosulfinates were prepared by synthesis, and their color-forming abilities were evaluated, together with those of various amino compounds. It has been found that an unsubstituted primary amino group and a free carboxyl group are essential structural features required for amino compounds to be able to generate the pigments. Out of the thiosulfinate analogues tested, only those containing at least a three-carbon chain with the β-carbon bearing a hydrogen atom yielded the pigments after reacting with glycine. Thiosulfonates, sulfoxides, sulfides, and disulfides did not form any colored products when mixed with glycine. The pH optimum for pigment formation has been found to be between 5.0 and 6.0 for all thiosulfinates tested.

Deoxygenation of sulfoxides to thioethers and reductive coupling of sulfonyl chlorides, sodium sulfinates and thiosulfonates to their corresponding disulfides were carried out by a heterogeneous phosphine reagent, Silphos [PCl3-n(SiO2)n] and molecular I2 in dry refluxing MeCN in high yields. Georg Thieme Verlag Stuttgart.

The invention relates to a process for the preparation of organic disulfides by oxidation of mercaptans with sulfur dissolved in an organic disulfide using an amine as catalyst, where the mercaptans are used as “crude mercaptan stream” from a reaction of alcohols with hydrogen sulfide over a catalyst suitable for mercaptan synthesis. Furthermore, the invention relates to the use of the organic disulfides for the preparation of alkanesulfonic acids.

Y2O3-TiO2-ZrO2 catalysts, where the contribution of oxide components ranges from 0 to 100 mol %, have been studied for their catalytic performance in methanol hydrosulfurization. Their activity and selectivity have shown a strong dependence on acid-base properties which, in turn, changed with catalyst composition. High yttria content favors selectivity to methanethiol, while catalysts highly active for the formation of dimethyl-sulfide were those containing 8 mol % Y2O3. The latter composition, which boosted selectivity to (CH3)2S, has created favorable conditions for the generation of acid centers in chemically mixed oxides as concluded on the ground of ESR studies and acidity measurements.

The dissociative reduction of a series of symmetrical (RSSR, R = H, Me, t-Bu, Ph) and unsymmetrical disulfides (RSSR′, R = H, R′ = Me and R = Ph, R′ = Me, t-Bu) was studied theoretically, by MO ab initio calculations and, for five of them, also experimentally, by convolution voltammetry in N,N-dimethylformamide. The reduction is dissociative but proceeds by a stepwise mechanism entailing the formation of the radical anion species. The electrochemical data led to estimated large intrinsic barriers, in agreement with an unusually large structural modification undergone by the disulfide molecules upon electron transfer. The theoretical results refer to MP2/3-21G*//MP2/3-21G*, MP2/3-21*G*//MP2/3-21G*, CBS-4M, and G2(MP2), the latter approach being used only for the molecules of small molecular complexity. A loose radical-anion intermediate was localized and the dissociation pattern for the relevant bonds analyzed. For all compounds, the best fragmentation pathway in solution is cleavage of the S-S bond. In addition, S-S bond elongation is the major structural modification undergone by the disulfide molecule on its way to the radical anion and eventually to the fragmentation products. The calculated energy of activation for the initial electron transfer was estimated from the crossing of the energy profiles of the neutral molecule and its radical anion (in the form of Morse-like potentials) as a function of the S-S bond length coordinate. The inner intrinsic barrier obtained in this way is in good agreement with that determined by convolution voltammetry, once the solvent effect is taken into account.

Whereas redox processes resulted from the reactions PhSe-/S8 or PhSe2Ph/S3·-, mixed anions RSSey- (R = Ph, PhCH2; y = 1-3) were obtained by the slow addition of solid selenium to thiolate ions in N,N-dimethylacetamide. The RS- + n Se reactions, which were investigated by spectroelectrochemistry, led initially (n = 1) only to the formation of RSSe- ions. These species oxidized into RS2R faster than RS- on a gold electrode, with the simultaneous electrodeposition of very reactive microcrystals of selenium. On a preparative scale, the substitution of RSSe- ions (R = CH3, Ph) on alkyl halides yielded RSSeR′ compounds (R′ = PhCH2, CH3, respectively) which greatly disproportionated. Further additions of Se (n = 2, 3) to RS- ions led to RSSe2- and RSSe3- in equilibrium with RS2R and mixtures of Sex2- polyselenide ions (x = 4,6; 6,8). Visible spectra of RSSe2- and RSSe3- ions were calculated from the study of the backward reactions RS2R + Sex2- (x = 4, 6).

Molybdenum pentachloride (MoCl5) in the presence of Nal in dry acetonitrile or zinc powder in anhydrous THF converts sulfoxides to their thioethers in high yields. Sulfonyl chlorides can be readily reduced to their corresponding disultides with MoCl5/Nal/MeCN at room temperature or with MoCl5/Zn/MeCN under reflux conditions in high yields.

A catalyst for hydrogenating aromatic compounds contained in feeds containing sulfur-containing compounds comprises platinum, palladium, fluorine and chlorine, on a support principally comprising alumina. This catalyst is of particular application to hydrogenating aromatic compounds with boiling points of more than 100° C. in hydrocarbon-containing feeds containing sulfur-containing compounds.

A compound of formula I wherein R1is hydrogen, methyl, ethyl, methoxy or methylthio; R2and R3each independently is hydrogen or lower alkyl; R4is hydrogen, lower alkyl, methoxy, ethoxy or benzyloxy; R5is lower alkyl, lower cycloalkyl, (CH2)mC(O)OR6wherein m is the integer 1 or 2 and R6is lower alkyl, phenyl optionally substituted; optionally Het or Het(lower alkyl); or R4and R5together with the nitrogen atom to which they are attached form a nitrogen containing ring optionally substituted with C(O)O-benzyl or with phenyl optionally substituted with C(O)OR7wherein R7is lower alkyl or (lower alkyl)phenyl; and Z is lower alkyl or optionally substituted phenyl or Het; with the proviso that when Z is (CH2)p-(Het), then R2and R3each is hydrogen; or a therapeutically acceptable acid addition salt thereof which compound is useful in the treatment of HCMV infections.

The complex 2(Me2SO)_GeCl4 in which the hexacoordinate germanium atom is coordinated via oxygen atoms with two Me2S=O molecules was studied by IR spectroscopy. The strong doublet band with maxima at 495 and 506 cm-1/

The degradation of two oxime carbamate pesticides, oxamyl and methomyl, was investigated in anoxic solutions containing various metal ions and reducing agents. In reagent-free solutions, these carbamates degrade slowly via base-catalyzed elimination. Rates of carbamate degradation are accelerated by FeII, CuI, and CuII, but not by several other metal ions and reducing agents. In the presence of FeII, carbamates undergo a net two-electron reduction that is coupled to the sequential one-electron oxidation of two FeII ions. The observed products are a substituted nitrile, methanethiol, and methylamine. A radical intermediate is inferred by polymerization of the radical scavenger acrylonitrile. Redox kinetics (i) vary with carbamate identity, (ii) exhibit first-order dependence on both FeII and carbamate concentration, (iii) are relatively independent of pH, (iv) follow Arrhenius temperature dependence, and (v) are only indirectly influenced by the presence of O2. Coordinatively saturated FeII complexes (FeIIEDTA2- and FeII(CN)64-) react with oxamyl at rates equal to and greater than hexaquo FeII, respectively, indicating that an inner-sphere FeII-carbamate coordination complex is not required for electron transfer. Experimental results indicate that CuI reduces the carbamates by the same mechanism as FeII but at much higher rates. In contrast, CuII acts as a catalyst for both elimination and reduction reactions.

Reaction of dimethyl disulfide (1) with cyclohexene (2a) in AcOH in the presence of Pd(OAc)2 yields trans-1-acetoxy-2-methylcyclohexane (3a). The equivalent reactions with hex-1-ene (2b) and 2-methylpent-1-ene (2c) or 1-methylcyclohex-1-ene (2d) preferentially give anti-Markovnikov and Markovnikov adducts 4 and 3, respectively, by ace-toxymethylthiolation of the alkene. The Markovnikov regioselectivity 3b/4b for the reaction with 2b (is higher than that for the reaction using AgOAc instead of Pd(OAc)2, which proceeds via a thiiranium ion. Addition of a polar solvent (MeCN or MeNO2) to the reactions with 2b or 2c (using Pd(OAc)2 abnormally decreases the Markovnikov regioselectivity. The total yield of 3 and 4 increases with an increased concentration of AcOH. Compounds 3 and 4 are also formed and the reactions in MeCN or MeNO2 not containing AcOH. A solution of Pd(OAc)2 in 1 exhibits λmax 380 nm (log ε 3.6) assigned to the absorption of a relatively stable sulfonium salt. These indicate that the reactions using Pd(OAc)2 proceed by SN2 ring-opening of a new type of thiiranium radical cations paired with -OAc via the sulfonium salts. The insensitivity of the 3/4 ratios to the reaction time at 25-60°C in the reactions with 2c-d shows the ring-opening to be controlled kinetically, but the increased ratio with reaction time at 116°C in the reaction with 2b suggests that the ring-opening is thermodynamically governed. The reaction product with 2d also undergoes a skeletal rearrangement to a thietanium radical cation to give 1-acetoxymethyl-2-methylthiocyclohexane.

The reaction between dry arenediazonium o-benzenedisulfonimides 1 and sodium thiolates in anhydrous methanol represents an efficient and safe procedure, of general validity, for the preparation of unfunctionalized or variously functionalized alkyl aryl and diaryl sulfides. As a rule, the reaction temperature was maintained at 0-5°C for the alkylthiodediazoniations and at room temperature (20-25°C) for the arylthiodediazoniations. The sulfide yields are generally high; of the 63 considered examples, 43 gave yields greater than 80% and 13 were between 70% and 80%. Lower yields were obtained only when sterically hindered diazonium salts or thiols were used. A good amount of the o-benzenedisulfonimide (8) was always recovered from the reactions and could be reused to prepare salts 1. The copious experimental data collected in homogeneous conditions have offered several starting points for the study of the mechanism of these reactions.

The Sm/HgCl2 system reduces β-ketosulfones to the corresponding ketones in moderate to good yield under mild conditions.

The reaction of 9-(methylsulfinyl)-10-(methylthio)anthracene with trifluoroacetic anhydride followed by quenching with aqueous NaHCO3 gives 9,9-bis(methylthio)-10-anthraquinone. The dithia dication and/or the corresponding carbodication via thr

The fluorodenitration of several nitroaromatics with tetramethylammonium salts has been found to be dependent on the basicity of the fluorinating species. Tetramethylammonium fluoride is highly basic and is capable of inducing H-D exchange in 1,3-dinitrobenzene, as well as deprotonating N,N- dimethylacetamide. Reaction of the fluoride with phthalic anhydride forms the bifluoride in situ. Tetramethylammonium bifluoride gives higher yields of the required fluoroaromatic, but slower reaction rates than the corresponding fluoride.

Tungsten hexachloride (WCI6) in the presence of NaI in anhydrous acetonitrile or zinc powder in anhydrous THF converts sulfoxides to their thioethers in high yields. Reductive coupling of sulfonyl chlorides to their corresponding disulfides is also achieved efficiently with the above reagent in anhydrous acetonitrile in high yields. Sodium benzene sulfinate as a model compound for sulfinate salts is also converted to diphenyl disulfide in almost quantitative yield.

A range of 18 alkoxycarbonyl sulfinyl phosphorus ylides 9 have been prepared and their behaviour upon flash vacuum pyrolysis (FVP) at 600 deg C examined. For R1 = H, Me and Et they lose Ph3PO and in some cases Ph3P to give mixtures of products including the alkenyl sulfides 10, the sulfides 11, the disulfides 12 and the thioesters 14. The alkenyl sulfides 10 most likely arise from intramolecular insertion of the alkoxycarbonyl sulfenyl carbenes resulting from loss off Ph3PO to produce β-lactones which then lose CO2 and this is supported by the results from 13C labelled ylides. Possible mechanisms for the formation of 11 and 14 are also presented and the feasibility of various steps has been examined by preparation and pyrolysis of the proposed intermediates. In contrast, pyrolysis of the ylides 9 where R1 = Ph and the tert-butoxycarbonyl ylides 30 leads mainly to complete fragmentation with loss of Ph3PO and benzyl alcohol or 2-methylpropan-2-ol and does not give any useful sulfur-containing products. Four alkoxy-carbonyl sulfonyl diazo compounds 33 have been prepared and in three cases they give the alkenyl sulfones 34 upon FVP at 400 deg C, probably by an intramolecular insertion and decarboxylation process analogous to the formation of 10 from 9. On the other hand the alkoxycarbonyl carbenes produced by FVP of the amino acid-derived diazo compounds 35 undergo alternative proocesses with no sign of β-lactone formation. Fully assigned 13C NMR data are presented for 13 of the ylides.

Reaction of trithiocarbonates with meta-chloroperoxybenzoic acid in CH2Cl2 at 0°C affords the corresponding S-oxides. These sulfines are relatively stable comppounds which can be purified by chromatography. They react readily with organolithiums in THF at -78°C in a thiophilic manner to give carbanions which are stabilized by three sulfur groups. Hydrolysis affords trithioorthoester oxides. The thermal behaviour of these hindered products has been investigated and new rearrangenrent processes have been evidenced. The former carbanions are soft nucleophiles: 1,4-addition of these intermediates to α-enones was achieved selectively to lead to β-oxo ketenedithioacetals, which are easily transformed into 4-oxoalkanethioates. This 'Umpolung' route allows the formal use of the (alkylthio)carbonyl anion. A thiophilic addition was also observed with allylsilanes in the presence of n-Bu4NF furnishing allyl sulfoxides.

Reaction products of 4-methylthio-3-butenyl isothiocyanate (MTBI), the radish pungent principle, in aqueous media were identified and their antimicrobial activities were examined.A rapid degradation of MTBI in aqueous media afforded a mixture of 3-(hydroxy)methylene-2-thioxopyrrolidine (1), (Z)-3-(methylthio)-methylene-2-thioxopyrrolidine (2), its (E)-isomer (3), methyl 4-methylthiobutyldithiocarbamate (4), methyl (Z)-4-methylthio-3-butenyldithiocarbamate (5), and its (E)-isomer (6).The products 1, 2, and 3 were detected at all pHs examined, while 4, 5, and 6 were formed at pH over 6.0.The formation of 4 from 6 was accompanied by an oxidation of methanethiol released from MTBI in aqueous media.Antimicrobial activities of 2 and 3 against all microbes examined were much lower than that of 1, which had MICs ranging from 50 to 400 μg/ml.As for 4, 5, and 6, antifungal activities were comparable to that of 1, but little antibacterial activities were observed.The antimicrobial activities of the six products were considered to be far lower than that of MTBI. - Keywords: radish pungent principle; thioxopyrrolidines; dhhiocarbamates; antimicrobial activity.

A new method is described for the preparation of unsymmetrical disulfides by reaction of the electrogenerated sulfenium cation R1-S+ with thiols or disulfides.

In the presence of copper(II), hydrogen sulfide reacts with thiols (methanethiol and ethanethiol) to yield symmetrical or unsymmetrical trisulfides (dimethyl trisulfide, diethyl trisulfide, and ethyl methyl trisulfide). In alcoholic beverages, these compounds are known for their nauseous character, reminiscent of onion smell, and for their low detection levels (dimethyl trisulfide: 0.1 μg/L). A mechanism for trisulfide formation is proposed that involves a two-step redox reaction.

Elemental sulfur is easily activated in the hydrazine hydrate-alkali system with formation of polysulfide anions. The procedure is developed for yielding highly concentrated solutions of alkali metal polysulfides. The latter compounds are readily alkylated with alkyl halides to form dialkyl polysulfides. The alkylation using higher alkyl halides (C7-C9) yields dialkyl sulfides that are difficult to prepare by other methods.

We have characterized and quantified several pathways which transform aliphatic sulfur radical cations into sulfoxides in aqueous solution. Sulfur radical cations were produced photochemically via one-electron photooxidation through triplet 4-carboxybenzophenone. Sulfur radical cations and superoxide yield sulfoxide, confirmed by oxygen product isotope effects and an inhibitory role of superoxide dismutase. On the basis of competition experiments with superoxide dismutase the rate constant for the reaction between dimethylsulfide radical cations and superoxide was derived as (2.3 ± 1.2) x 1011 M-1 s-1. A demetalated variant of superoxide dismutase did not inhibit superoxide mediated sulfoxide formation, confirming the importance of an active site of the enzyme for inhibition. The stoichiometry of 2 equiv of sulfoxide per reaction of superoxide with a sulfur radical cation suggests a pathway like the singlet oxygen mediated sulfoxide formation, i.e., via a persulfoxide intermediate formed via (i) direct coupling of superoxide with the sulfur radical cation or (ii) electron transfer followed by addition of the product singlet oxygen to a nonoxidized sulfide. In aqueous solution the persulfoxide may add water to yield a hydroperoxy sulfurane prior to its reaction with a second nonoxidized sulfide. At pH values larger than 9, hydroxide ion starts to compete with superoxide for sulfur radical cations and reacts with the persulfoxide or hydroperoxy sulfurane intermediates, initiating less effective pathways of sulfoxide formation. One pathway involves the formation of hydroxysulfuranyl radicals and their reaction with oxygen, supported by product and solvent isotope effects. Besides superoxide and hydroxide-mediated sulfoxide formation there is an additional route involving methylthiomethylperoxyl radicals. Based on oxygen product isotope effects, the latter appear to transfer oxygen onto the sulfide rather than reacting via electron transfer.