Diphenyl disulfide oxidations

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... 

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

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 ... 

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... 

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. ... 

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). 

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... 

The ability to polymerize readily via selective oxidation utilizing the abundant and cheap oxidant 02 often represents a desirable low-cost method for upgrading the value of a raw material. The most successful example is the oxidative polymerization of 2,6-dimethylphenol to yield poly(2,6-dimethyl-l,4-phenylene ether) with copper-amine catalysts under an 02 atmosphere at room temperature. Thiophenol also has a labile hydrogen but is rapidly oxidized to yield thermodynamically stable diphenyl disulfide. This formation is based on the more facilitated formation of S—S bond through radical coupling [82] in comparison with the formation of C—S—C bond through the coupling with the other molecules in the para position (Eq. 9). 

Thiophenol is electrochemically oxidized to diphenyl disulfide near 1.7 V (vs. Ag/AgCl), because the thiophenolate radicals undergo coupling. Although diphenyl disulfide is further oxidized under the given potential of 1.7 V, the cationic species formed are rapidly inactivated by a nucleophilic reaction with... 

Chemical oxidation can also be applied to this polymerization instead of electro-oxidation. Diphenyl disulfide reacts with 2,3-dichloro-5,6-dicyano-/ -benzoquinone (DDQ) in dichloromethane at room temperature. The polymer has been isolated as a pure white powder (ca. 100% yield). 

Methylbis(methylthio)sulfonium hexachloroantimonate ([CH3S(SCH3)2][SbCl6]) was isolated from the reaction mixture at -40°C by the oxidation of nonpoly -merizable dimethyl disulfide [86], This result suggests that the phenylbis(phenyl-thio)sulfonium cation is produced by the oxidation of diphenyl disulfide in the acidic reaction mixture [87-89], This cation acts as the active species for the polymerization and electrophilically reacts with the / -position of the benzene ring to yield PPS [90],... 

Aromatics for oxidative polymerization usually show high oxidation potentials. The direct oxidation of these monomers by 02 does not proceed because of the large potential gap between the monomers and 02. A novel catalysis by vanadyl complexes is applicable to the synthesis of PPS by the 02-oxidative polymerization of diphenyl disulfide (Eq. 10) [93-103], In the presence of VO(acac)2, the polymerization is accompanied by a quantitative 02 uptake. Dioxygen is essential for the VO-catalyzed oxidative polymerization of diphenyl disulfide. 

Table 1 Cationic Oxidative Polymerization of Diphenyl Disulfide in the Presence of Catalytic Amounts of Metal Complexes ...

An equimolar amount of vanadium(V) oxide (V205) reacts with diphenyl disulfide to yield PPS (>90%) even under anaerobic media. V(acac)3 (vanadi-um(III) species) is oxidized to VO(acac)2 by 02. The activated VO(acac)2 in the presence of acid seems to exhibit the properties of both vanadium(III) and vanadium(V) in the catalytic system. 

The PPS yield depends on the acidity of the mixture. The oxidative polymerization does not proceed in the absence of acids. Strong acids, such as triflu-oromethanesulfonic acid and trifluoroacetic acid, are required for the VO-cata-lyzed polymerization. The oxidative polymerization of diphenyl disulfide is facilitated by the activated VO(acac)2 produced by the acid. Diphenyl disulfide is not oxidized by 02 only or an equimolar amount of VO(acac)2 in the absence of acid. The VO catalyst is estimated to be an excellent electron mediator, through activation by acids, to promote the electron transfer between diphenyl disulfide and molecular oxygen. 

Although VO(acac)2 acts as an excellent catalyst for the 02-oxidative polymerization of diphenyl disulfide, mechanistic analysis of the redox process involved in... 

Since the oxidative polymerization of diphenyl disulfide catalyzed by VO(acac)2 results in selective formation of thioether bonds without any oxygenated compounds such as sulfoxides and/or sulfones, it should be noted that H20 should be produced predominantly by the reduction of 02 catalyzed by the vanadium complex without the formation of partially reduced side products such as H202. 

A molecular conversion system based on a four-electron transfer to 02 was accomplished in the 02-oxidative polymerization of diphenyl disulfide (Figure 14) [116]. This is the first example of a multielectron mediator that is applied to molecular conversion systems. The multielectron transfer process from the reduced vanadium(III) complex (VOV+) to 02 not only revealed the 02 oxidation mechanism but also provided additional insight into the unique chemistry of vanadium with possible relevance to metal mono-oxygenases. 

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