Thiosulfinates reactions

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

In the case of 1,2,4-trithiolanes, both els and trans isomers are obtained with a different reaction mechanism involving a molecule of thioketone and a molecule of thiosulfine.50... 

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 ... 

We noted earlier that the sulfinyl group of a thiolsulfinate is believed to have a basicity somewhat less than that of a sulfoxide but somewhat greater than that of a sulfinate ester (Engberts and Zuidema, 1970).+Thus, in an acid solution a thiosulfinate will be protonated to some extent to RS(OH)SR. A whole series of reactions is known that are initiated by attack of a nucleophile on the dico-ordinate sulfur of RS(OH)SR with cleavage of the S—S bond and displacement of RSOH. 

Let us return now to a brief further consideration of the acid- and nucleophile-catalyzed reactions of thiosulfinates. We have seen that in the various acid- and nucleophile-catalyzed reactions of PhS(0)SPh the attack of... 

So far all of the mechanistic studies discussed have involved the use of thiosulfinates lacking hydrogens on both the carbon a to the sulfenyl sulfur and the carbon(s) / to the sulfinyl sulfur. There has been a good reason for this. When hydrogen atoms are present in such locations cycloelimination reactions can take place quite readily and a whole new dimension of complexity is added to the chemistry of thiolsulfinates. The details of these cycloelimination reactions and the chemistry that follows them have been brilliantly worked out in detail by Block and his co-workers (Block and O Connor, 1974a, 1973 Block and Weidman, 1973 Block, 1972a,b). We will now outline their findings. 

The oxidation of sulfoxides by aliphatic peroxy acids is first order in both reactants the solvent effects have also been investigated. Thiosulfinates are oxidized by peroxy acids to thiosulfonates and not disulfoxides. It had previously been proposed that the disulfoxides are formed first but homolytically cleave and recombine to give thiosulfonates. A series of ab initio calculations were performed (at the 3-210 and 6-3IG levels) which indicate little difference in the rate of oxidation of S over S(0) in the gas phase but faster S(0) oxidation in a reaction cluster. ... 

Reactions of cyclopentadienyl- and (pentmethylcyclopentadienyl)iron dicarbonyl 2-alkynyl complexes as well as cyclopentadienylmolybdenum tricarbonyl 2-alkynyl complexes with 4,5-diphenyl-3,6-dihydro-l,2-dithiin 1-oxide 111 were shown to yield transition metal-substituted five-membered ring thiosulfinate esters 112 in moderate to excellent yields (Scheme 27) <19910M2936, 1989JA8268>. These reactions are formal [3-1-2] cycloadditions. When... 

A further approach for the synthesis of nonsymmetrically protected lanthionines is the conversion of thiosulfinates of symmetrically protected cystine derivatives into nonsymmetrically protected cystines via a reaction with a cysteine derivative and subsequently the conversion of the resulting unsymmetrically protected cystine into the nonsymmetrically protected lanthionines with a tris(dialkylamino)phosphineJ26l The oxidation of the symmetrically protected cystine, e.g. A,AT-bis(benzyloxycarbonyl)-L-cystine diethyl ester, of one stereochemical configuration to the thiosulfinate with m-chloroperoxybenzoic acid is essentially quantitative. The nonsymmetrical cystine is then formed in a subsequent step by the addition of the /V-/er/-butoxycarbonyl-L-cysteine tert-butyl ester derivative to give N-Z-N -Boc-L-cystine ethyl ferf-butyl diester. The desired 2f ,6f -lanthionine is then formed in the presence of P(NEt2)3 in yields of >50%. 

The reaction of 4-oxochromanones 282 with thionyl chloride gives a-chlorosulfenyl chlorides 283. Treatment of these sulfenyl chlorides with potassium iodide or thioacetic acid followed by morpholine gives rise to the chroman-4-one thiosulfine intermediates 284, which can dimerize in a Diels-Alder reaction to give the chromeno[3,4-r ]-l,3,4-oxa-dithiin+-one 285, for example, R, R = (0+2)6, R = R = H, in low yield (Scheme 48) <1998)009840, 2002ZNB922>. 

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... 

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 ... 

Another simple elimination reaction on the thiosulfinate ester makes another molecule of the sulfenic acid and a highly unstable unsaturated thioaldehyde, which promptly dimerizes to give a thioacetal found in garlic as a potent platelet aggregation inhibitor. 

Reaction of (R)-(+)-tert-butyl ferf-butanethiosulfinate (52) with lithiated imine 53 gave 54 as a single isomer in 92% yield.39 The thiosulfinate 52 was prepared by asymmetric oxidation of rerf-butyldisulfide with H202 in the presence of a chiral vanadium complex. 

Bis(trimethylsilyl) sulfide reacts with methyl, phenyl, or other thiosulfinates (disulfane oxides), R S(0)SR, in anhydrous chloroform at 60 °C to give the symmetrical trisulfane and hexamethyldisiloxane the latter is removed together with the solvent by vacuum distillation, leaving almost pure R2S3 (yields 70 90%). In a similar reaction,... 

Reaction of Thiols with Sulfur(lV) and Sulfur (VI) Compounds (SO2, Tetrahalides, Thiosulfinates, Sulfinylimides, Bunte Salts, etc.)... 

Mloston et al. reported that the formation of seven-membered sulfur heterocycles 181 and 182 possibly appears to be the result of a domino reaction involving both the dithiirane 183 and its valence isomer, thiosulfine 184 <2002JOC5690>. Dithiirane 183 is presumed to exist in equilibrium with the thiosulfine 184 and is generated from the reaction of 185 with elemental sulfur in the presence of sodium benzenethiolate. 

Baldwin and Lopez used fragmentation of thiosulfinate (17) to furnish transient thioaldehyde (18), which was trapped by intramolecular Diels-Alder reaction to yield bicyclic compounds (19) and (20) in equal amounts (82CC1029 83T1487). 

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). ... 

Another class of sulfoxidic substances, the aryl thiosulfinates ArS(0)SAr, which have recently been prepared in an optically active form, exhibit exceptionally high optical lability Racemization of thiolsulfinates may occur in an uncatalysed path involving pyramidal inversion at the sulfoxide sulfur. Reaction rate coeffi-... 

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