Disulfides thiosulfinates

Bass, S.W. and Evans, S.A., Jr., Carbon-13 nuclear magnetic resonance spectral properties of alkyl disulfides, thiosulfinates, and thiosulfonates, J. Org. Chem., 45, 710, 1980. 

Organic sulfur compounds, for example, disulfides, thiosulfinates, thiosul-fonates, thiols, sodium thilates, and sodium sulfinates, were found to be readily oxidized to both sulfinic and sulfonic acid using the poatassium superoxide/18C6 system [234]. 

Under the reaction conditions the initially formed thiosulfinate (143) is quantitatively transformed into the disulfide 144 by a Pummerer-type rearrangement125. 

Within the biooxidation of disulfides, chiral thiosulfinates become available. Tert-Butyl tert-butanethiosulfinate represents a particularly valuable chiral auxiliary for the preparation of several chiral sulfoxides and sulfinimines, which can be subsequently transformed into branched amine compounds, P-aminoacids, and chiral aziridines. This product is accessible readily by mediated biooxidation of tert-butyl... 

The oxidation of sulfides is a complex process involving a number of conversions [32,46], Disulfides are oxidized by hydroperoxide via the intermediate thiosulfinate RSSOR, which is very reactive to ROOH [32,52-54], The interaction of ROOH with phenolsulfoxides also gives rise to intermediate catalytic compounds, as a result of which the reaction proceeds as an autocatalytic process [46,55], The rate of the catalytic decomposition of R OOH is described by one of the following equations ... 

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... 

The most important flavour compound in raw onions is thiopropanal-S-ox-ide, the lachrymatory factor [145,146]. Other important flavour compounds are 3,4-dimethyl-2,5-dioxo-2,5-dihydrothiophene and alkyl alkane thiosulfonates such as propyl methanethiosulfonate and propyl propanethiosulfonate with a distinct odour of freshly cut onions [35, 36, 147]. Various thiosulfinates that have a sharp and pungent odour may also contribute to the flavour of onions. These compounds, however, are rapidly decomposed to a mixture of alkyl and alkenyl monosulfides, disulfides and trisulfides (Scheme 7.3) of which dipropyl disulfide, methyl ( )-propenyl disulfide, propyl ( )-propenyl disulfide, dipropyl trisulfide and methyl propyl trisulfide are the most important contributors to the aroma of raw and cooked onions (Table 7.5, Fig. 7.6) [148-150]. Recently, 3-mercapto-2-methylpentan-l-ol was identified in raw and cooked onions eliciting intense meat broth, sweaty, onion and leek-like odours [142, 151]. 

The following routes to unsymmetrical disulfides and symmetrical trisulfides use silyl sulfides and thiosulfinates [41.42]. Thiosulfonates react similarly. 

The N-sulfonyloxaziridines are an important class of selective, aprotic oxidizing reagents.12 Enantiomerically pure N-sulfonyloxaziridines have been used in the asymmetric oxidation of sulfides to sulfoxides (30-91% ee),13 selenides to selenoxides (8-9% ee),14 disulfides to thiosulfinates (2-13% ee),5 and in the asymmetric epoxidation of alkenes (19-65% ee).15-16 Oxidation of optically active sulfonimines (R S02N=CHAr) affords mixtures of N-sulfonyloxaziridine diastereoisomers requiring separation by crystallization and/or chromatography.13... 

The Bolm protocol was recently used by Ellman et al. for the enantioselective oxidation of -butyl disulfide 22 [72], Excellent result was achieved in the formation of thiosulfinate 22 (91% ee, 93% yield) by using catalyst 20 (0.25 mol %) in a 0,5 mmol scale. In spite of extensive screening of chiral Schiff bases related to catalyst 20, better enantioselectivity was not realized. Chiral thiosulfinate 22 is a convenient starting material for the preparation of r-butyl sulfi-namides and t-butyl sulfoxides. Vetter and Berkessel modified the structure of the Schiff base moiety of catalyst 20 by replacing the aryl ring with a 1,l -binaphthyl system [73]. The corresponding vanadium catalyst realized 78% ee in the oxidation of thioanisol, which was better than that attained by the Bolm catalyst (59% ee). 

Buffer catalysis of the hydrolysis of phenyl (311 R = Ph) and methyl (311 R = Me) benzenesulfinates to give the sulfinic acid (312) and alcohol ROH is strongly accelerated by both carboxylate and amine components of the buffer which give Bronsted /i values of approximately unity on separate lines. The carboxylates are about 44 tunes more effective than amines of similar basicity. A concerted. S n2 mechanism with a hypervalent intermediate (313) is proposed for the nucleophilic reaction of these esters.286 The reaction of the thiosulfinate esters (314) with sulfenyl chlorides RSCI and sulfenate esters (315) to give sulfinyl chlorides and disulfides and sulfinate esters and disulfides, respectively, has been studied.287 Hydrolysis of 2-(3-aminophenyl)sulfonyl-ethanol hydrogensulfate gives under different conditions various products such as the ether (316) and the sulfone (317).288... 

Asymmetric oxidations. These reagents selectively oxidize sulfides and disulfides to sulfoxides and thiosulfinates [RS(0)SR], respectively. They also epoxidize olefins in a. yn-stcrcospecific manner.3... 

According to Barnard (47), initial attack of 03 on the DMDS appears to be the rate-determining step of the overall reaction. Thiosulfinates formed as a result of this attack are generally orders of magnitude more reactive than disulfides in reactions leading to cleavage of S-S bond (48). In an experiment with [DMDS]0 = 1 x 10 4 M, [03]0 = 6 x 10 4 M, Erickson et al. (49) observed the reaction to be complete in about one half minute and a final pH of the reaction mixture to be 5.3. The overall reaction for the oxidation of DMDS by 03 is ... 

Both mono- and disulfides owe a large part of their antioxidant activity toward olefins to their immediate oxidation products—i.e., sulfoxides and thiosulfinates—since these products show an immediate effect, whereas, with the parent compounds a small amount of oxygen must be absorbed before there is appreciable activity (9). 

Oxaziridines. Davis has developed the use of chiral 2-sulfonyloxaziridines derived from camphorsulfonic acid as chiral auxiliaries in the asymmetric oxidation reactions. Although other oxaziridines may be preferable, the camphor-derived oxaziridines can be used for the oxidation of sulfides and disulfides to sulfoxides and thiosulfinates as well as for the epoxidation of alkenes. On the other hand, the camphoryloxaziridines are the preferred reagents for hydroxylation of lithium enolates of esters, amides, and ketones, as utilized in the synthesis of kjellmanianone (eq 17). ... 

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. 

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