Diaryl disulfides, oxidation

Sulfonyloxaziridines were recently proposed as O-transferring reagents. Oxaziridine (89) converted thioethers to sulfoxides (90) and diaryl disulfides into their 5-oxides (91) (78TL5171). Epoxidations are also possible (81TL917). 

Optically active aromatic thiosulfinates were first prepared by asymmetric oxidation of diaryl disulfides with (+)-percamphoric acid (105,112). Apart from the fact that the optical purity of diaryl... 

In an aprotic solution, the mechanism of oxidation of diaryl disulfides was shown to be more complex than a direct cleavage of the S—S linkage [116,117,123], The occurrence of two consecutive reactions being of second kinetic order if potential-determined and of first order if current-determined, was established for the two-electron transfer steps. Dimerization of the cation radicals occurs on the ArS fragment, whose contribution to the HOMO is more important, and produces an intermediate disulfonium dication. The subsequent cleavage of the latter results in two ArS+ cations and a molecule of a disulfide (the same as a starting disulfide in the case of symmetrical compounds). This mechanism, EC2C1E (E = electrochemical, C = Chemical), has... 

A novel and convenient synthetic route for PPS via a cationic mechanism has been discovered [85-92] diaryl disulfides and thiophenols are polymerized to PPS with high purity in high yield under an air atmosphere at room temperature by chemical oxidation and by electro-oxidation. 

Arylsulfenyl trifluoroacetates have been generated in situ and used for the hydroxysulfenylation of al-kenes. These reagents are prepared from diaryl disulfides and LTA in trifluoroacetic acid. Yields for the addition are generally good (42-95%). The hydroxysulfenate intermediate can be oxidatively cleaved by LTA (provided the groups can achieve an antiperiplanar arrangement) to form an a-aldehyde-acetoxy sulfide in good yield (40 88% Scheme 3). 7... 

Cation radicals are intermediates in the anodic oxidation of simple dialkyl and diaryl disulfides, RSSR, but are too short-lived to be observed at the time scale of slow-sweep voltammetry, although their existence has been established by pulse radiolysis [29] and electron spin resonance (ESR) spectroscopy [30]. Their detection by voltammetric technique was achieved in the case of more complex molecules like NDS [31], and when two disulfide linkages are present as in TTN, TTA, and TTT, even the generated dications are stable [32, 33]. 

Lower yields are observed when R is a secondary group, and no thiosulfonate is formed with R = r-Bu. Although thiosulfinates, RSOSR, are intermediate products, they are not oxidized under the electrolysis conditions. It was shown that thiosulfinates are transformed into thiosulfonates in the presence of disulfides being oxidized, presumably involving an intermediate species electrogenerated from the disulfide [38b]. Diaryl disulfides also lead to thiosulfonates in good yields when oxidized under similar conditions [39]. The disulfoxide, RSOSOR, supposedly obtained in the anodic oxidation of dibenzyl disulfide in a HOAc/HCl solution at a Pt anode [40], is probably also a thiosulfonate. 

The anodic oxidation of 2,2-bis(ethylthio)propane producing acetone and an oxidation product of diethyl disulfide, claimed to be the corresponding disulfoxide, was reported many years ago [133]. A renewed interest in this reaction involving a C-S bond cleavage arose when bis(phenylthio)methane and some of its p-substituted ring derivatives were anodically oxidized in dry MeCN on Pt electrodes and afforded diaryl disulfides and formaldehyde, with the latter identified after aqueous workup [39, 134]. The same cleavage was observed when MeCN-H20 (9 1 v/v) was the solvent, but aryl benzenethiosulfonates were the main products [39] ... 

A third method is based on oxidative amination of diaryl disulfides with N,N-di-chlorotrifluoromethane sulfonamide, leading to imidosulfrnyl chlorides (Scheme 2.180). 

Anodic oxidation of diaryl disulfides results in polymerization [473, 474]. Thus oxidation of diphenyl disulfide 187, R=Ph, in the presence of trifluoro-acetic acid gave poly(p-phenylene sulfide) 209a. 

Sulfenyl ions, RS+, or their synthetic equivalent generated by anodic oxidation of diaryl disulfides have been used to effect acetamidosulfenation of alkenes... 

The synthesis of 1,2/C-a/aphosphospholancs 127 is based on the reaction of the substituted 3-aminopropylphosphines with diaryl disulfides or with elemental bromine in the presence of triethylamine [171, 172] (Scheme 77). Furthermore, the cyclic P(III) compounds may be converted to the corresponding oxides 122 or sulfides 128, useful as lubricating oil antioxidants and flame retardants in plastics and textiles. 

Diaryl disulfides and diselenides undergo Pd-catalyzed iyn-addition of S—S and Se—Se bonds, which may be most readily explained in terms of (i) oxidative addition of S—S and Se—Se bonds, (ii) yn-heteropalladation, and (iii) reductive eliminationf i (Scheme 19). 

Nakata T, Kuwabara T, Tani T, Oishi T (1982) Total synthesis of (+)-oudemansin. Tetrahedron Lett 23 1015-1016 Nambiar KP, Stauffer DM, Kolodziej PA, Benner SA (1983) A mechanistic basis for the stereoselectivity of enzymatic transfer of hydrogen from nicotinamide cofactors. J Am Chem Soc 105 5886-5890 Ng GY, Yuan L-C, Jakovac IJ, Jones JB (1984) Enzymes in organic synthesis. 29. Preparations of enantiomerically pure cis-2,3- and 2,4-dimethyl lactones via horse liver alcohol dehydrogenase-catalyzed oxidations. Tetrahedron 40 1235-1243 Oae S, Nagata T, Yoshimura T, Fujimori K (1982) Reduction of diaryl disulfides with 1-benzyl-1,4-dihydronicotinamide. Tetrahedron Lett 3189-3192... 

Based on their contradictory results, a different mechanism was proposed. Lu proposed a Ni(II)/Ni(III) catalytic cycle, in which the cyclometalated complex 20 reacts with a phenylsulfide radical to generate a Ni(lll) intermediate, which is similar to the pathway from 35 to 37 in Scheme 14. However, Shi and Zhang proposed a Ni(ll)/Ni(lV) cycle, in which diaryl disulfides undergo oxidative addition to the cyclometalated complex 20 to afford a Ni(lV) intermediate. 

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