S- sulfenyl

On the other hand, it seems to be generally agreed that combination of two sulfmyl radicals leads to thiosulfonate (RS02SR) as the final product22 the usual suggestion has been that it takes place via an initial head-to-tail combination of the radicals to give a O, S-sulfenyl sulfinate (5) which then rearranges to the thiosulfonate. 

Scheme 2 summarizes the mechanism for the formation of thiosulfonate from sulfinyl radicals it is shown that the sulfinyl radicals combine to give both yic-disulfoxides and O, S-sulfenyl sulfinates, although they may rearrange to thiosulfonates either via a free radical route or via a concerted mechanism. The reader is referred to the recent review of Freeman22, who has collected and discussed the vast amount of information published on yic-disulfoxides and O, S-sulfenyl sulfinates. 

Treatment of cyclobutanones (232) with NaOMe and diphenyldisulfide in MeOH at reflux temperature led to 6/s-sulfenylation and subsequent ring cleavage to furnish compounds (233) (Table 14)78). 

An illustration of this approach may be seen in the studies on streptococcal proteinase (Liu 1967). The activity of this enzyme is dependent upon the presence of a free sulfhydryl group. The active form of the enzyme was first converted to the inactive S-sulfenyl-sulfonate derivative. Treatment of this derivative with a chemically-reactive substrate "analogue, a-N-bromoacetylarginine methyl ester, resulted in the alkylation of a single histidine residue. The sulfhydryl group of the modified enzyme was regenerated by reduction, however, this did not restore enzymatic activity, thus providing presumptive evidence for the involvement of both a cysteinyl and a histidyl residue in the active site of this enzyme. 

Methylindole undergoes clean 3-sulfenylation with M-methylthiomorpholine in TFA. Indole itself gives mainly 3-methylthioindole (57%) with 1.5 equiv. of the reagent, but the 1,3- (61%) and 2,3- (22%) h s-sulfenyl derivatives are the main products with 2.5 equiv. [74]. 

Sulfenyltrifiuorides s. Phenyl-sulfenyl trifluoride Sulfenyltrihalides s. Sulfenyl-trifluorides... 

Organosulfur Halides. When sulfur is directly linked only to an organic radical and to a halogen atom, the radical name is attached to the word sulfur and the name(s) and number of the halide(s) are stated as a separate word. Alternatively, the name can be formed from R—SOH, a sulfenic acid whose radical prefix is sulfenyl-. For example, CH3CH2—S — Br would be named either ethylsulfur monobromide or ethanesulfenyl bromide. When another principal group is present, a composite prefix is formed from the number and substitutive name(s) of the halogen atoms in front of the syllable thio. For example, BrS—COOH is (bromothio)formic acid. 

Fluoride ion attacks the sulfur atom in 2,3-diphenylthiirene 1,1-dioxide to give ck-1,2-diphenylethylenesulfonyl fluoride (23%) and diphenylacetylene (35%). Bromide or iodide ion does not react (80JOC2604). Treatment of S-alkylthiirenium salts with chloride ion gives products of carbon attack, but the possibility of sulfur attack followed by addition of the sulfenyl chloride so produced to the alkyne has not been excluded (79MI50600). In fact the methanesulfenyl chloride formed from l-methyl-2,3-di- -butylthiirenium tetrafluoroborate has been trapped by reaction with 2-butyne. A sulfurane intermediate may be indicated by NMR experiments in liquid sulfur dioxide. 

The free-radical chemistry of fluoroalkanesulfenyl chlorides with hydrocarbons was also investigated [S, 9], Depending upon the structures of the sulfenyl chloride and the hydrocarbon, these reactions yield as major products up to three of the following four types of organic compounds thiols, disulfides, sulfides, and chlorohydrocarbons (equation 6), Perfluoroisobutanesulfenyl chloride is unique m that the only major products detected are the thiol and chlorohydrocarbon [ ] (equation 6) (Table 3). 

In the reaction of CF Cl3 SCl with triethylamine, the yield of the product (CF Cl3 S)2C=CHN(C2H5)2 decreases with decreasing n [fri] (equation 7) (Table 2). 2,3,4,5-Tetrakis(trifluoromethylthio)pyrrole salts react with sulfenyl chloride or SjjCl2 (x = 1,2) to give N-sulfenylaled pyrroles as well as dipyrrolylsulfane and -disulfene. Pentakis(trifluoroniethylthio)pyrrole is a mild sulfenylating... 

The S-(A-methyl-A-phenylcarbamoyl)sulfenyl group (Snm group) produced under these conditions is stable to HF or CF3SO3H. Since there are few acid-stable-SH protective groups, the Snm group should prove useful where strong acids are encountered in synthesis. 

From intermediate 12, the path to periplanone B (1) is short but interesting. Enolization of 12 with lithium bis(trimethylsilyl)amide at -78 °C, followed by sulfenylation using Trost s reagent,12 affords a 16 1 mixture of regioisomeric monosulfenylated ketones favoring intermediate 17. The regioselectivity displayed in this reaction is... 

There is not one generic route into 1,3,2-dithiazolyl/ium chemistry. For acyclic derivatives the [4+2] cycloaddition chemistry of [SNS][AsF6] to alkynes has been successfully expoited by Passmore.49 Flowever for benzo-fused derivatives, the simplest route is via Wolmershauser s method in which 1,2-sulfenyl... 

However, a few thiols (cysteine, N-acetylcysteine and thiosalicylic acid) also react with organic nitrates to release NO by another process that is difficult to discern. It could be that the nitrite reacts with a thiol to give an S-nitrosothiol, a ready source of NO, but nitrosation is unlikely to occur at biological pHs. Another possible route to NO involves formation of a thionitrate by trans-esterification [59] (Eq. (12)). This species could then decompose to give NO via an intermediate sulfenyl compound [60] (Eq. (13)). 

Asymmetric sulfenylation. In the presence of the chiral diamine (S)-l-methyl-2-(piperidinylmethyl)pyrrolidine (1), tin(II) enolates of ketones react with... 

Nevertheless, new examples have also been reported of allenyl sulfoxides [101] and especially allenyl trichloromethyl sulfoxides [39, Y+-X = S(0)CC13] [102]. There have been many trials to use these sigmatropic rearrangements for the synthesis of diallenes (compare 40 — 42), e.g. the reaction of the diols 43 with trichloromethane-sulfenyl chloride 44 to the diallenes 45 (Scheme 7.7) [103]. 

Sulfenic acids exhibit high nucleophilic reactivity toward sulfenyl derivatives RS—X possessing a readily displaced group X (Kice and Cleveland, 1973a). The product of such a reaction is a thiolsulfinate as shown in (11). Analysis of appropriate kinetic data (Kice and Cleveland, 1973a) shows that, when R = Ph and —X = —Cl, —Br, or —S(n-Bu)2, Jt, is from 4 x 104 to 4 x 105 times faster... 

Trichloromethanesulfenyl chloride is a sulfenyl chloride that does not form a thiolsulfinate upon hydrolysis, however. Instead it gives the sulfine C12C=S=0 (Silhanek and Zbirovsky, 1969) because trichloromethanesulfenic acid loses HC1 (13) faster than it undergoes any other reaction. 

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. 

We will defer consideration of the particular pattern of nucleophile reactivity observed until Section 9. There we will compare it with what is found for the same group of nucleophiles reacting with (a) an aryl rr-disulfone ArS02S02Ar, a substitution that involves the same leaving group as in (139) but which takes place at a sulfonyl ( S02) rather than a sulfinyl ( S=0) sulfur, and (b) an aryl thiolsulfonate, ArSSOzAr, a substitution where ArSO is displaced from a sulfenyl ( S) sulfur. 

Earlier (Table 6, p. 119) we saw data on the reactivity of various nucleophiles toward an aryl sulfinyl sulfone in (139), a substitution that also involves an arenesulfinate as the leaving group, but one in which the substitution takes place at a sulfinyl ( S=0) rather than a sulfenyl ( S) sulfur. In Section 9 we present data on the rates of reaction of the same nucleophiles in an analogous substitution at a sulfonyl sulfur, Nu- + PhS02S02Ph - PhS02Nu + PhS02. At that point we will discuss how changing the oxidation state of the sulfur atom at which the substitution occurs... 

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