Reactions of Disulphides

Reactions of Disulphides.—Most of the reactions of disulphides are based upon S—S cleavage, and subsequent interaction of cleavage products with reagents, though photolysis of di-t-butyl disulphide is shown by photo-CIDNP studies to give Bu SS +Bu via the triplet excited state of the disulphide. 

Reduction of disulphides to component thiols remains an important topic for study, and PhaP or BusP are suitable in aqueous media for reduction of disulphides and for preventing autoxidation of thiols on storage. Quantitative reduction of disulphides by an insolubilized thioP is an ingenious procedure likely to be much used in biochemistry. 

Cleavage rates of disulphides using CN or OH are poorly correlated with Hanunett o--values in the diaryl series. Cleavage by trans-IrCl(CO)(PPhj)2 has been reported, also oxidative cleavage of di-(2,4-dinitrophenyl) disulphide under mild conditions, giving 2.5% of the sulphoxide and 87% 2,4-dinitrobenzenesulphonic acid. 

Reactions by which disulphides are converted into sulphides have been considerably augmented in number recently. Di-(2,4-dinitrophenyl) disulphide gives the corresponding sulphide by refluxing in alcohol solvents,  

Insertion reactions of disulphides by nitrenes lead to sulphenamides, and l,2-di(alkylthio)alkenes, e.g. Bu SCH==CHSBu formed by the reaction of acetylene with the disulphide under pressure in the presence of KOH, consist of cis-trans mixtures in which the cis-isomer greatly predominates (p -(L) interaction is proposed as an explanation of the high thermodynamic stability of the cis-isomer. 

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Further studies of the kinetics of reaction of disulphides with triphenylphosphine and water have been reported,86 87 supporting the previously suggested two-step mechanism.88 The reactions of -labelled acetyl aralkyl disulphides with triphenylphosphine have also been investigated.89... 

Further use has been made of the reaction of disulphides with tervalent phosphorus compounds in phosphorylation reactions, e.g. in the synthesis of (57).68... 

The Reporter notes an overall decrease in the number of papers in this area published during the year, although the number dealing with p -bonded phosphorus compounds continues to increase. The reactions of disulphides with tervalent phosphorus compounds have been reviewed. ... 

Sulphonyl halides are readily prepared by the nitric acid oxidation of sulphenyl halides, which are in turn easily formed by reaction of disulphides with sources of halogens. Thus, alkanesulphenyl chlorides are oxidized to the corresponding sulphonyl chlorides, in high yields301,550-552, as depicted in equation 142. 

T. Mukaiyama and H. Takei, The reaction of disulphides with trivalent P compounds. Topics Phos. Chem., 8, 587, 1976. 

Furthermore, ions similar to (3) are postulated as intermediates in the interchange reaction of disulphides and sulphenyl chlorides - , and intermediates like (2) should be involved in the reaction of disulphide with halogens (equation 17) which has to be considered an equilibrium reaction. 

Differences in the rates of the reactions of disulphides and hydroxyl ions, can be used for the analysis of a mixture of oxidized... 

Preparation from Disulphides, Diselenides, and Ditellurides.—The use of disulphides as sulphenylating agents towards alkenes and carbanions continue to offer a distinctive alternative to the use of sulphenyl halides for the same purpose. Although reaction conditions are more severe, cleaner results are usually obtained. The special case of the conversion of disulphides into corresponding sulphides is covered in the later section on Reactions of Disulphides. 

The reactions of phosphines with disulphides have been studied extensively due to the importance of these reactions in organic syntheses. Under appropriate conditions tertiary phosphines can act as desulphurizing agents (producing R P=S and the thioether) or reduce disulphides to thiols. Hie reaction of disulphides with phosphines has also been used as the dehydration step in the syntheses of peptides and nucleotides. The subject has been reviewed by Mukaiyama and Takei. ... 

Sulphenyl halides give cationoid species RS+ Y (Y = BF4 or SbF,) on reaction with the corresponding Ag salt an areneselenenyl hexafluoro-phosphate and a corresponding hexafluoroantimonate have been described. Further details of the equilibrium 2RSC1 RS(C1)SR + Cl- set up by an alkane-sulphenyl chloride in liquid SOj in the presence of a Lewis acid, or in H2SO4 or FSO3H, are available. Such cations have been suggested to be implicated in the reactions of disulphides and sulphenyl halides, and the reaction in these media... 

Reaction of alkali cellulose with carbon disulphide to produce a cellulose xanthate which forms a lyophilic sol with caustic soda. This may be extruded into a coagulating bath containing sulphate ions which hydrolyses the xanthate back to cellulose. This process is known as the viscose process and is that used in the manufacture of rayon. 

The reaction of a-aminonitriles and carbon disulphide was stated by Cook and Heilbron to give 5-amino-2-mercaptothiazoles however, they later found that the same reaction with aminoacetonitrile was more complex. When aminoacetonitrile sulphate in ethanolic solution was treated with carbon disulphide, the dithiodicarbamate 9 was formed. Benzylation was then carried out treatment of the resulting ester 10 with phosphorus tribromide with subsequent loss of water gave 5-amino-2-benzylthiothiazole 11 in a quantitative fashion. The rapid reaction was thought to be the first example of the formation of a 5-aminothiazole from an a-aminoamide. 

All reactions involving the uniform formation and growth of a film of reaction product (e.g. reaction of metals with high-temperature water, reaction of copper with sulphur dissolved in carbon disulphide). 

Few racemic alkyl p-tolyl sulphoxides were prepared in rather low yields (16—40%) by the reaction of Grignard reagents with mixed anhydrides 108, 109 and compound HO formed in situ from p-toluenesulphinic acid and 3-phthalimidoxy-l,2-benzoisothiazole 1, 1-dioxide167 (equation 59). The mixed anhydrides 109 or 110 when reacted with cyclopen-tene and cyclohexene enamines 111 gave the corresponding a-ketocycloalkyl sulphoxides 112 in low yields (10-41%) along with small amounts of several by-products such as disulphides and thiosulphonates167 (equation 60). 

Reaction of sulphoxides with disulphides 493 in the presence of BuLi or NaH yields mono-, and disulphenylated products (equation 297). The formation of monosulpheny-lated sulphoxide as the main reaction product (55%) takes place only when Et2S2, sulphoxide and BuLi are used in a 1 3 3 ratio556. 

For a review of the formation and reactions of xanthates, see Dunn, A.D. Rudorf, W. Carbon Disulphide in Organic Chemistry Ellis Horwood Chichester, 1989, p. 316. 

The reaction of troponephenylhydrazone with carbon disulphide afforded the bicyclic thiazole (37) in quantitative yield. iV-methoxytroponimine when treated with phenylisothiocyanate afforded a mixture of cycloheptatriene derivatives (38a) and (38b). Both of these reactions proceed via an [8+2] cycloaddition <95H1675>. 

A. Synthetic Methods.—There have been no strikingly new approaches to the general problem of phosphorylation, but several ingenious methods of preparing suitable active esters under mild conditions have been reported. Typical of these is the reactive intermediate (1) formed from reaction of a mono- or di-ester of phosphoric acid with (2), itself produced by reaction of triphenylphosphine with bis(2-pyridyl) disulphide (preferably in the presence of mercuric ion as scavenger for the 2-mercaptopyridine liberated). 

Reaction of perthiophosphonic anhydrides (64) with amines leads first to (105) and then, by further attack, to (106). With ammonia itself the second addition proceeds at the same phosphorus atom as the initial attack, giving (107) and (108). The anhydride (64) is also reported to react with 1,3-dioIs to give cyclic phosphonyl disulphides (109). Thermal decomposition of phenylphosphinic anhydride (110) may lead to the formation of PhP since in the presence of benzil the formation of the phosphorane (111) was observed. ... 

Phosphinyl radicals, obtained by hydrogen abstraction from dialkyl phosphites, have been trapped with t-nitrosobutane and the resultant nitroxyl radicals examined by e.s.r, The reaction of phosphinyl radicals, e.g. (5) and (6), with olefins has been shown to occur with retention of configuration at phosphorus. " These radicals have also been postulated as intermediates in the reactions of dialkyl disulphides and diaryl disulphides with phosphinates. " From the reaction of diphenyl disulphide... 

The reaction of dipyridyl disulphide with triphenylphosphine to give the stable phosphonium salt (51) has been used in new methods of phosphorylation (reaction A), in peptide synthesis (reaction B), and in the formation of active esters of cx-amino-acids (reaction C). These reactions appear to have synthetic potential. 

The interaction of disulphide with oxygen can be very dangerous. This compound has a very low self-ignition temperature (see tables in Part Three). When rust is present it can cause the mixture to detonate by catalysing the oxidation reaction. 

Nucleophilic Attack at Carbon.- The reactions of silyl-aminophosphines with carbon disulphide result in the formation of... 

In a related paper, reaction of(60a) with (56) gave the hydrospirophosphorane (61) which upon u.v. irradiation in the presence of dimethyl disulphide gave the methylthio derivative (62) which was also prepared by the reaction of(60b) with hexafluoroacetone1 2. In contrast, the reaction of (63) with hexafluoro-acetone furnished a 1 1 mixture of the 1,3,2-A3- and 1,3,4-A5-dioxaphospholanes (64) and (65). 

Oxidative bleaching of wool is invariably carried out with hydrogen peroxide. The active species involved is likely to be the same as on cellulosic substrates but specific reactions with wool amino acid residues must be considered. The primary reaction is oxidation of cystine disulphide bonds leading to the formation of cysteic acid residues (Scheme 10.41). The rupture of disulphide crosslinks, with attendant increase in urea-bisulphite and alkali solubility values, adversely affects fibre properties. As the severity of bleaching conditions increases, the urea-bisulphite solubility remains little changed but the relationships between alkali solubility and cysteic acid (Figure 10.36) and between cystine and cysteic acid (Figure... 

Tetramethylthiuram disulphide (TMTD) has proved to be a useful reagent for the thiocarbamoylation of amine containing compounds. Thus, reaction of a series of hydrazones of aromatic aldehydes with TMTD in a 1 1 ratio gave amongst other products, 4,4-dimethylthiosemicarbazide 86 and 5-dimethylamino-l,3,4-thiadiazole-2-thiol 85. It was confirmed that 86 was an intermediate in the synthesis of 85 as treatment of 86 with TMTD gave 85 in 85% yield <00RCB344>. 

Tashtoush and Talib reported an unexpected reaction of propanodihydrazide and butanodihydrazide with carbon disulphide giving 2,5-dimercapto-13,4-thiadiazoles in good yield <99IJC1374>. 

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