Dialkyl sulfide

Elemental sulfur reacts with alkanes such as cyclopentane in the presence of superacidic trifluoromethanesulfonic acid to give symmetrical dialkyl sulfides in moderate yields. 

Fluorinated and Ghlorfluorinated Sulfonic Acids. The synthesis of chlorinated and fluorinated sulfonic acids has been extensively reviewed (91,92). The Hterature discusses the reaction of dialkyl sulfides and disulfides, sulfoxides and sulfones, alkanesulfonyl haHdes, alkanesulfonic acids and alkanethiols with oxygen, hydrogen chloride, hydrogen fluoride, and oxygen—chloride—hydrogen fluoride mixtures over metal haHde catalysts, such as... 

Fig. 11. Surface-active organosulfur compounds that form monolayers on gold (a) alkanethiol (b) dialkyl disulfide (c) dialkyl sulfide (d) alkyl xanthate ...

Formation of Sulfides. Thiols react readily with alkenes under the same types of conditions used to manufacture thiols. In this way, dialkyl sulfides and mixed alkyl sulfides can be produced. Sulfides are a principal by-product of thiol production. Mixed sulfides can be formed by the reaction of the thiol using a suitable starting material, as shown in equations 21, 22, and 23. Vinyl sulfides can be produced by the reaction of alkynes with thiols (38). 

Carbon disulfide reacts with alkanols or diaLkyl ethers at 250—500°C over activated alumina catalyst to give diaLkyl sulfides. For example, methanol yields dimethyl sulfide [75-18-3]. 

Monochlorophenols. Chlorination of phenol [108-95-2] between 50 and 120°C gives a ortho ratio of 1.65. To improve the selectivity in the paia position, it is possible to use dialkyl sulfides, diaiyl sulfides (12), oi alkyl and aiyl sulfides combined. Sulfides are active only at low tempeiatuies (<50 C), because at high tempeiatuies the active species decomposes into sulfui and chlorine. 

Xenon difluoride [55], xenon difluoride complexed with dialkyl sulfides [59], and xenon difluoride intercalated with graphite [90] are all effective reagents for the fluonnalion of acids, enolates, or enols (Table 2)... 

Besides the thiocyanates, just mentioned, other 5-donor complexes which are of interest are the dialkyl sulfides, [MCl3(SR2)3], produced by the action of SR2 on ethanolic RhCl3 or on [IrClg] ". Phosphorus and arsenic compounds are obtained in similar fashion, and the best known are the yellow to orange complexes, [ML3X3], (M = Rh, Ir X = Cl, Br, I L = trialkyl or triaryl phosphine or arsine). These compounds may exist as either mer or fac isomers, and these are normally distinguished by their proton nmr spectra (a distinction previously made by the measurement of dipole moments). An especially... 

Viewed from the standpoint of molecular orbital theory, as it has developed during the last decade or so3, the above simple pictures of the sulfur bonding in a dialkyl sulfide are somewhat naive but they serve to introduce the subject and act as a basis for discussing the bonding in sulfoxides and sulfones. It will be convenient to use the second of the two pictures as the basis for further discussion, i.e. that involving the use of 3sp3 hybridized orbitals on sulfur. 

Biocatalytic access to both antipodal sulfoxides was exploited in total syntheses of bioactive compounds, which is outlined in some representative examples. Biooxidation of functionalized dialkyl sulfides was utilized in the direct synthesis of both enantiomers of sulforaphane and some analogs in low to good yields and stereoselectivities (Scheme 9.27) [206]. This natural product originates from broccoli and represents a potent inducer of detoxification enzymes in mammalian metabolism it might be related to anticarcinogenic properties of plants from the cruciform family. All four possible stereoisomers of methionine (R = Me) and ethionine sulfoxides... 

The final elimination step in which the conjugated PPV derivative (63) is generated from the sulfonium polyelectrolyte precursor polymer (62) was reported by Wessling and Zimmerman to be heating in vacuo to 200 - 300°C. The target PPV derivative is formed with elimination of dialkyl sulfide and hydrogen halide the process can be easily monitored by UV/Vis spectroscopy. PPVs... 

Sections I and J of Scheme 3.2 show reactions with sulfur and phosphorus nucleophiles. The reaction in Entry 25 is a useful method for introducing thiol groups. The solid thiourea is a convenient source of sulfur. A thiouronium ion is formed and this avoids competition from formation of a dialkyl sulfide. The intermediate is readily hydrolyzed by base. 

Whilst many solvating ligands have been studied, the dialkyl sulfide reagents (see Table 6) remain the most important commercially 297... 

The same catalysts have been investigated for the asymmetric oxidation of dialkyl sulfides using PhIO as the oxidant in CH3CN perfluorooctane.[54] Although the conversions (>80%) and selectivities to sulfoxides (>90%) were generally good, and the more heavily fluorinated catalysts could be recycled 4 times with only small drops... 

Sulfur(II)-containing compounds possess the reducing activity and react with hydroperoxides and peroxyl radicals [1-5]. They are employed as components of antioxidant additives to lubricants and polymers [30-35]. Denison and Condit [36] were the first to show that dialkyl sulfides are oxidized by hydroperoxides to sulfoxides and then to sulfones... 

One can prepare derivatives of 4 that contain a weakly-bound ligand L, such as a pyridine or a dialkyl sulfide. These compounds show no... 

When an optically active sulfoxide is used, the sulfimide is found to be of retained configuration. The mechanism shown in (145) has been proposed for the reaction with the sulfoxide (Maricich and Hoffman, 1974). It accounts satisfactorily for the fact that small amounts of dialkyl sulfide and arenesulfonamide are also formed in the reaction. As discussed in detail by Maricich and Hoffman, it is also consistent with the stereochemistry observed for formation of the sulfimide. 

Depending on the linear, branched or cyclic structure of the unsaturated compound, a variety of dialkyl sulfides has been obtained in the reaction with H2S (equations 16-18). The regiochemistry depended markedly on the structure of the diene. For a mechanistic purpose, some experiments have been carried out using deuterium sulfide, D2S. The results have been interpreted in terms similar to those of Nordlander and coworkers9 (vide infra). The thiylation of 1,3-dienes was assumed to start with a regiospecific addition of a proton or a deuteron to one of the two double bonds to form two isomeric ion pairs as in equation 14 which, in the poorly dissociating solvent, collapse into products with equal probability. 

Dialkyl sulfides RSR are known [205] to be electrochemically inactive in all cathode materials and solvents considered. 

Also other Type B and C series from Table II are consistent with the above elimination mechanisms. The dehydration rate of the alcohols ROH on an acid clay (series 16) increased with the calculated inductive effect of the group R. For the dehydrochlorination of polychloroethanes on basic catalysts (series 20), the rate could be correlated with a quantum-chemical reactivity index, namely the delocalizability of the hydrogen atoms by a nucleophilic attack similar indices for a radical or electrophilic attack on the chlorine atoms did not fit the data. The rates of alkylbenzene cracking on silica-alumina catalysts have been correlated with the enthalpies of formation of the corresponding alkylcarbonium ions (series 24). Similar correlations have been obtained for the dehydrosulfidation of alkanethiols and dialkyl sulfides on silica-alumina (series 36 and 37) in these cases, correlation by the Taft equation is also possible. The rate of cracking of 1,1-diarylethanes increased with the increasing basicity of the reactants (series 33). 

Enantiomerically pure sulfoxides play an important role in asymmetric synthesis either as chiral building blocks or stereodirecting groups [156]. In the last years, metal- and enzyme-catalyzed asymmetric sulfoxidations have been developed for the preparation of optically active sulfoxides. Among the metal-catalyzed processes, the Kagan sulfoxidation [157] is the most efficient, in which the sulfide is enantioselectively oxidized by Ti(OzPr)4/tBuOOH in the presence of tartrate as chirality source. However, only alkyl aryl sulfides may be oxidized by this system in high enantiomeric excesses, and poor enantioselectivities were observed for dialkyl sulfides. 

Enzymes, in particular peroxidases, catalyze efficiently the enantioselective oxidation of alkyl aryl sulfides and also dialkyl sulfides, provided that the alkyl substituents are sterically differentiable by the enzyme. The peroxidases HRP, CPO, MP-11, and the mutants of HRP, e. g. F41L and F4IT, were successfully used as biocatalysts for the asymmetric sulfoxidation (Eq. 14). A selection of sulfides. 

The rate constants for the reaction of EtsSi radicals with dialkyl sulfides R2S were measured by the laser flash photolysis technique and decrease in the order R = primary > secondary > tertiary, viz., 1.1 x 10, 8.8 x 10 , and 3.3 x... 

Taft and coworkers ° have reported lithium ion affinities, AGu+, for various types of compounds. Values of AGu+ for alkyl thiols, dialkyl sulfides, alcohols and dialkyl ethers (sets CP3, CP4, CPS and CP6, Table 10) were correlated with equation 27. The regression equation for the alkyl thiols is equation 58 ... 

For the dialkyl sulfides, equation 26 takes the form of equation 59 ... 

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