Sulphenyl halides reactions

The photostimulated reactions of thiolate anions with 2-halo-2 -nitropropane derivatives yield both oc-nitrosulphides via an S l pathway and disulphides (equation 71a)282 284. In contrast with the case of the oxidative dimerisation products of the mono-enolates, the disulphides are formed via an ionic mechanism nucleophilic attack by the thiolate anion on the a-halogen and subsequent reaction of a second thiolate with the sulphenyl halide. As expected for such a process, disulphide formation is favoured (and thus a-nitrosulphide formation is disfavoured) the more nucleophilic the thiolate (i.e. derived from a less acidic thiol) and the easier the abstraction of the halo-substituent (i.e. I > Br > Cl). Use of the protic solvent methanol instead of the usual dipolar aprotic solvents for the reaction of equation 71a is detrimental to the yield of the S l substitution products exclusively disulphides are formed285 (equation 71b). Methanol solvation probably retards the dissociation of the radical anion intermediate in the SRN reaction, into radical and anion, and hence retards the chain reaction relative to the ionic reaction. The non-nucleophilic methylsulphinate ion gives only an S l reaction product with 2-bromo-2-nitropropane286. 

Addition reactions of sulphenyl halides (in particular chlorides) to acetylene derivatives have been extensively explored and recently reviewed (Modena and Scorrano, 1968). Although free radical processes may be involved under specific conditions, the addition of both arene-and alkanesulphenyl halides normally occurs by an ionic mechanism, the sulphenyl halide sulphur being the electrophilic centre. 

Steps (a) and (b) of Scheme 6 constitute the Arens mechanism. Therefore, equation (244) was simply a case of attack on Cl in which the ion-molecule (PhC=C CISC,-H,-p) was the key intermediate. Attack of acetylide on the sulphur of the sulphenyl chloride leads to the product given in equation (244). Support for this step is the well-known reaction of sulphenyl chloride with carbanions to yield sulphides . The disulphides which sometimes turn up in the haloalkyne-thiolale processes (see Table 6) are easily explained by the sulphenyl halide reacting with the thiolates. 

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. 

The reactions of acetylenes with sulphenyl halides and related compounds have been reviewed. A-(Benzenesulphenyl)-/ -nitroaniline (326) reacts with 1 -pentyne in acetonitrile in the presence of boron trifluoride etherate to yield solely the 2-azabutadiene derivative 327235. 

By far the most evidence for electrophilic sulphur is found in the sulphenyl halides (RSCl, RSBr) Although these compounds may in theory react either as sources of RS or X (X = halogen), none of the observed reactions of the sulphenyl halides indicate the latter mode of heterolysis. Kharasch et have presented good evidence for the existence of the 2,4-dinitrobenzene-sulphenium ion (Ar ) in strongly acidic media evidence has also been presented of a strong solvent effect upon the rate of reaction of 2,4-dinitroben-zenesulphenyl chloride and cyclohexene - and of a definite substituent effect in the reaction of this sulphenyl chloride with some substituted styrenes in acetic acid . Such observations are entirely consistent with an electrophilic heterolytic ad tion mechanism involving attack by the sulphenyl chloride in the sense iC -Cl. 

The order of susceptibility towards substituent effects is much less in the acetylene series than in the olefins, but its direction is similar. A similar statement may be made about the direction, rates, and kinetics of addition of sulphenyl halides. While the simple acetylenes, such as sym-diphenylacetylene and 3-hexyne, required catalytic quantities of aluminium chloride before undergoing addition by 2,4-dinitrobenzene sulphenyl chloride , the rates of reaction of acetylene itself with some p-substituted benzene sulphenyl chlorides alone have been measured. The effect of the p-substituents... 

Various derivatives of sulphur may be prepared by the reaction of sulphur monochloride, sulphur dichloride or sulphenyl halides with thiolates the products depend on the reactant stoichiometry. 

The hydrolysis of sulphenyl halides is believed to form sulphenic acids (equation 22). These compounds, however, have never been isolated in this reaction rather thiolsulphinate esters are formed by fast reaction of sulphenic acids with sulphenyl halides (equation 23). 

The reaction of sulphenyl halides with thioethers seems to be a general procedure for the cleavage of a thiol protecting group, provided that a stable cation could be ejected from the thiosulphonium ion intermediate. Thus the thioether linkages between the haem group and the cysteine... 

Reviews cover the topics alkynethiolates in synthesis " oxygen-exchange reactions of sulphoxides sulphonyldiazomethanes C—S bond cleavage acyl isothiocyanates radical reactions of sulphur compounds addition of sulphenyl halides to olefins " sulphenamidcs mercaptoethylation of amines sulphur as a chiral centre " stereochemistry of S and S " compounds " reductive cleavage of sulphides, synthetic uses of alkene- and alkyne-thiolates, and thio-Claisen rearrangements nucleophilic displacements at sulphur in disulphides aromatic... 

Sulphenyl Halides.— Illustrative procedures for the synthesis of sulphenyl halides reported during the period under review employ well-established methods, Tetrachloropyridine-4-sulphenyl chloride is obtained from the corresponding disulphide by chlorinolysis, while the corresponding sulphonyl chloride is formed in AcOH or hydroxylic media. 2-Methyl-2-propanesulphenyl iodide is obtained from the thiol with la, or from the sulphenamide with HI addition reactions of selenium dichloride, or seleninyl chloride, to acetylene are specific examples of generally applicable reactions - (HC=CH + SeCU C1CH=CH-Se-Cl). The chlorination of CSa under activated charcoal catalysis has been developed as a continuous process, giving trichloromethanesulphenyl chloride. 

The characteristic reaction behaviour of sulphenyl halides is exemplified in a wide range of alkyl- or aryl-thiolation processes. 2,3-Dimethylindole gives (153) with 2,4-dinitrophenylsulphenyl chloride, and a-phenyl-thiolation of ketones (PhSCl + Ri CO CHR R R -CO-CR R SPh) ... 

Molecular Orbital (M.O.) studies of reaction intermediates have been reported for the rearrangement of l-propenethiol, for the addition of sulphenyl halides to ethylene (sulphurane rather than thiiranium salt as intermediate), and for similar additions to alkynes (thiirenium ions or /ff-alkylthiovinyl cations, depending upon the substituents). Electronic effects of substituents on energy levels of orbitals of... 

G. Capozzi, V. Lucchini, G. Modena, and P. Scrimin. Nouv. J. Chim., 1978,2,95 [RSCl + alkynes in liquid SOj) Substitution reactions of sulphenyl halides J. F. Harris,/. Org. Chem.,... 

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. 

References to addition reactions of sulphenyl halides with alkenes and alkynes are given in the Sulphides section. An incidental bonus from a study of the addition of PhSCl to adamantylideneadamantane is the formation of the 4e-chloro-derivative and PhSSPh, via an intermediate thiiranium salt. Sulphenyl and selenenyl chlorides have been used for the dehydration of aldoximes to nitriles. Whereas sulphinyl chlorides yield sulphinate esters with alkoxytri-methylsilanes, no reaction occurs with sulphenyl chlorides. ... 

Easily prepared thiocarbonyl derivatives of alcohols, such as the 5-methyl dithio-carbonates (64 Y == SMe), can be treated with soft electrophiles A-X to improve the leaving ability of the alcohol oxygen in the presence of a nucleophile and thus provide a simple mild method of hydroxy group replacement (Scheme 27). For instance, use of CH3I as the electrophile produces alkyl iodides, and sulphenyl halides PhSX can be utilized to synthesize chlorides, bromides, or iodides. Similar reactions have been described for some selenocarbonyl alcohol derivatives. ... 

Sulphenyl Halides.—This section describes first the preparations of sulphenyl halides of particular interest in the recent literature, then their properties and their addition and substitution reactions. More space is allocated this year for results from studies of organo-sulphur, -selenium, and -tellurium halides involving higher valency states. 

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... 

Routine studies of the addition of sulphenyl halides to alkenes have been reported, most studies dealing with the kinetics of the reaction as a function of structure and stereochemistry. Among these reports is a notable... 

Substitution reactions of CgFsSCl and / -MeCeHgSCl with aromatic compounds and active-methylene compounds represent a separate area of sulphenyl halide chemistry. A related process, the ring-opening of the cyclopropane moiety of quadricyclanes by PhSCl, has been studied. ... 

Allenic sulphoxides ArSOCH=C==CR R are available through the reaction of sulphenyl halides with propargyl alcohols HC CCR R OH. Friedel-Crafts reactions with toluene>p-sulphinyl chloride in the presence of AICI3, SnCh, or SbCl, give aryl p-tolyl sulphoxides, and an analogous product is obtained unexpectedly, using toluene-p-sulphonyl chloride with isoquinoline as substrate in the presence of excess NaH. ... 

Sulphenyl Halides.—Sulphenyl chlorides are readily available by chlorinolysis of disulphides, and this remains the most commonly used method of synthesis. Chlorinolysis of penicillin esters gives the sulphenyl chloride, and a route to an azetidinone sulphenyl chloride has been devised in which the relatively unstable sulphenic acid produced by penicillin sulphoxide pyrolysis is treated with SOCh in CCl, to give [43 R =C1, R =CH(C02Me)CMe=CH2]. Sulphenyl iodides may be important intermediates in reactions at disulphide bridges in peptides and proteins, and a report of the preparation of a stable sulphenyl iodide is notable. The observation that methanesulphenyl chloride dimerizes (in SO2 in the presence of a Lewis acid) to give MeSSMeCl Cl MeS=SMeCl Cl may be useful in explaining the course of certain electrophilic reactions of sulphenyl chlorides, and should stimulate a search for new reactions of aliphatic compounds of this series. 

Addition of positive sulphur species, RS", usually derived from sulphenyl halides, to olefins is commonly assumed to proceed by way of thiiranium ions, the reactions often showing the stereochemistry expected for trans-addition For instance, the reaction of cyclohexene with methanesulphenyl tetrafluoroborate is believed to form an intermediate thiiranium ion (73), which then reacts with nucleophiles to give trans-methylthio-derivatives, e.g. (74). Addition of thiocyanogen chloride to olefins may... 

To date, however, only few reactions between phosphine and a non-metal halide, in which a chemical bond is formed between phosphorus and a non-metal by HCl condensation, are known. To these, apart from the above-mentioned reactions, belongs also the reaction with CF3SCI which, depending upon the chosen proportions of the reactants, in a sealed tube at -95 °C leads to the formation of (CF3S)2PH or (CF3S)3P Both compounds are not very stable thermally and decompose at 40-50 °C. Tris(trifluoromethylthio)-phosphine forms an unstable adduct with chlorine, which decomposes at 0 °C to give a mixture of PCI3, bis(trifluoromethyl)-disulphide and trifluoromethyl-sulphenyl chloride. 

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