Disulfides, diphenyl oxidation

The lO-E-4 chalcogen(IV) species diphenylselenium(IV) dibromide (1, Fig. 1) and diphenyltellurium(IV) dibromide (2, Fig. 1) oxidize thiophenol to diphenyl disulfide in nearly quantitative yield as shown in equations (13) and (14). Tellurium(IV) dihalides 6-11 also oxidize thiophenol to diphenyl disulfide and benzene selenol to diphenyl diselenide. Similarly, the 12-Te-5 molecule dioxatellurapentalene 45 (Fig. 19) is a mild oxidant for ethylmercaptan, thiophenol, and benzene selenol giving diethyl disulfide, diphenyl disulfide, and diphenyl diselenide in essentially quantitative yield. As shown in equation (15), 1,1,5,5,9,9-hexachloro-1,5,9-tritelluracyclododecane oxidizes six molecules of thiophenol to diphenyl disulfide and 1,5,9-tritelluracyclododecane in 90% yield. In contrast, 12-Te-5 pertellurane 44 and 12-Se-5 perselenane 46 do not oxidize thiophenol to diphenyl disulfide. Instead, these molecules undergo a nucleophilic addition of thiophenol followed by cleavage of the tellurium-carbon or selenium-carbon bond. ... 

Beeswax, white Beeswax, yellow Benzoic, acid Benzyl tiglate y-Bisabolene Brominated vegetable oil 3-Butylidenephthalide Butyloxepanone 3-Butylphthalide Calcium lactate Caramel Castor (Ricinus communis) oil Citronellyl isovalerate Citronellyloxy acetaldehyde p-Cresyl isovalerate p-Cresyl octanoate Crotonic acid p-Cyclocitral p-Damascenone 9-Decenal trans-4-Decenal Diacetyl tartaric acid esters of mono- and diglycerides Diethyl malate Difurfuryl disulfide Dihydroeugenol Dihydro-a-ionone Dihydrojasmone Diisobutyl ketone Diisopropyl disulfide 3,4-Dimethylcyclopentane-1,2-dione Dimethyl dicarbonate 2,5 Dimethyl-3-furanthiol p-a-Dimethylstyrene Diphenyl oxide Ethyl acetate... 

The chain extension mechanism is shown in Figure 8 (201). Diphenyl disulfide is oxidized to a cation radical, which reacts with diphenyl disulfide to give phenylbis(phenylthio)sulfonium cation, followed by electophilic attack of diphenyl sulfide on the cation. 

Alternative synthetic routes to poly(arylene sulfide)s have been pubHshed (79—82). The general theme explored is the oxidative polymerization of diphenyl disulfide and its substituted analogues by using molecular oxygen as the oxidant, often catalyzed by a variety of reagents ... 

Diphenylcyclopropenone, 47, 62 Dii henyldiacetylene, 45, 39 Diphenyl disulfide, oxidation to methyl benzenesulfinate, 46, 62 1,1-Diphenylethylene, reaction with N,or diphenylmtrone, 46,129 N,N -Diphi iiyli tiiyleni diamine, condensation with triethyl orthoformate, 47, 14... 

The photochemical behavior of a number of substituted derivatives of thiochroman-4-one 1-oxides has been examined by Still and coworkers192-194. These authors also report that rearrangement to cyclic sulfenates, with subsequent reaction by homolysis of the S—O bond, appears to be a particularly favorable process. For example, ultraviolet irradiation of a solution of 8-methylthiochroman-4-one 1-oxide (133) in benzene for 24h afforded a single crystalline product which was assigned the disulfide structure 134 (equation 54). More recently, Kobayashi and Mutai195 have also suggested a sulfoxide-sulfenate rearrangement for the photochemical conversion of 2,5-diphenyl-l,4-dithiin 1-oxide (135) to the 1,3-dithiole derivatives 136 and 137 (equation 55). 

Dicyclopentadienyltin also takes part in oxidative addition reactions with such reagents as iodomethane, diiodomethane, ethyl bromoace-tate, and diphenyl disulfide, and there is evidence that the reactions involve a radical chain-mechanism (324, 325). 

Trimethylsilyl esters of tris(thio)phosphonic acids 2070 are readily oxidized by DMSO in toluene at -30 °C to give the dimeric tetra(thia)diaphosphorinanes 2071 and HMDSO 7 [208] (cf. also the oxidation of silylated thiophenol via 2055 to diphenyl disulfide). The polymeric Se02 is depolymerized and activated by reaction with trimethylsilyl polyphosphate 195 to give the corresponding modified polymer... 

Diphenylcyclopropane, 48, 75 Diphenylcyclopropenone, 47, 62 Diphenyldiacetylene, 46,39 Diphenyl disulfide, oxidation to methyl... 

In the photochemical one-electron oxidation of aromatic sulfides, dimer radical cations were formed in rapid equilibrium with monomeric radical cation (59). The complex formation of a- and tt-types has been shown to be sensitive to the steric and electronic influence of substituent. For the case of jo-(methylthio)anisole the formation of TT-type dimer was shown to be reduced due to steric hindrance of two methyl groups. No formation of dimer radical cation was observed for jo-(methoxy)thioanisole and diphenyl disulfide where the corresponding monomer radical cations are stabilized by the delocalization of positive charge on the sulfur atom. Density-functional calculations supported the experimental results. The intramolecular formation of similar radical... 

Plant. In plants, fonofos is oxidized to the phosphonothioate (Hartley and Kidd, 1987). Oat plants were grown in two soils treated with [ C]fonofos. Most of the residues remained bound to the soil. Less than 2% of the applied [ C]fonofos was recovered from the oat leaves. Metabolites identified in both soils and leaves were methyl phenyl sulfone, 2-, 3- and 4-hydroyxymethyl phenyl sulfone, thiophenol, diphenyl disulfide, and fonofos oxon (Fuhremann and Lichtenstein, 1980 Lichtenstein et al., 1982). 

The proposed mechanism of the oxidative cleavage of S-protecting groups by the chlorosilane/sulfoxide procedure is outlined in Scheme 8. 95 The first reaction is considered to be formation of the sulfonium cation 9 from diphenyl sulfoxide (7) and the oxygenophilic silyl compound 8. The formation of a sulfonium ion of this type is known and has been utilized for the reduction of sulfoxides. 97 Subsequent electrophilic attack of 9 on the sulfur atom of the S-protected cysteine residue leads to the formation of intermediate 10, whereby the nature of the silyl chloride employed should be the main factor that influences the electrophilicity of 9. The postulated intermediate 10 may then act as the electrophile and react with another S-protected cysteine residue to generate the disulfide 11 and the inert byproduct diphenyl sulfide (12). This final step is analogous to the reaction of a sulfenyl iodide as discussed in Section 6.1.1.2.1. 

Similar behavior of other aromatic disulfides and thiols on gold electrodes has been described based on the SERS experiments [167]. Adsorption of benzenethiol, benzenemethanethiol, p-cyanobenzenemethanethiol, diphenyl sulfide, and dibenzyl sulfide was studied on the roughened gold electrode. All these species adsorb dissociatively as the corresponding thiolates. Monolayers formed from symmetric disulfides were exactly like those formed from the corresponding thiols. These monolayers were stable in a wide potential window from -1-800 to —1000 mV (versus SCE), which was limited by the oxidation of the Au surface from the positive side and hydrogen evolution at —1000 to —1200 mV at the negative side. 

It was first assumed that an inhibitor was produced as a by-product. However, the accuracy with which the initiation rates had to be balanced seemed to demand too great a coincidence if the inhibitor production occurred in a side reaction independent of the initiation reactions. Thus, although possible products which were demonstrably powerful inhibitors of the co-oxidation reaction—e.g., thiolsulfinates—could be postulated, this mechanism was unsatisfactory and did not fully explain the role of iron. Furthermore, diphenyl disulfide, which is a precursor of thiolsul-finate in the presence of hydroperoxide, did not inhibit the reaction. The possibility that the negative term represented a diminishing contribution from a radical-producing process was then studied. 

Disulfides are generally oxidized with cleavage of the S —S bond. Hypofluorous acid in acetonitrile solution oxidizes sulfur atoms in bis(trifluoromethyl) disulfide to the highest oxidation state and, in addition, inserts an oxygen bridge between the sulfur atoms (Table 19).304 A sulfonyl chloride 18 is similarly obtained by the reaction of a substituted diphenyl disulfide with hypochlorous acid generated from chlorine and aqueous acetic acid.305... 

In the oxidation of alkanethiols to disulfides with chloramine-T (CAT), in alkaline solution, the proposed reactive species are hypochlorous acid and TsNCl- anion. A correlation of reaction rate with Taft s dual substituent parameter equation yielded p = -5.28 and 5 = -2.0, indicating the rate-enhancing effect of electron-donating substituents.133 Michaelis-Menten-type kinetics have been observed in the oxidation of atenolol with CAT in alkaline solutions. TsNHCl is assumed to be reactive species. A mechanism has been suggested and the activation parameters for the rate-determining step were calculated.134 The Ru(III)-catalysed oxidation of diphenyl... 

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