Sulphonyl sulphenes

Sulphonyl phosphates, reactions of 638 Sulphonyl radicals 215 cyclization of 1099 ESR spectra of 1090-1093 formation of 1094-1098 structure of 1090-1094 thermodynamic data for 1094 Sulphonyl sulphenes 196 Sulphonyl sulphoxides alkylation of 311 synthesis of 262... 

The reader will have noted that some unanswered questions were left in some of our earlier sections. For example, recall Reference 34 cited in Section V. A we did not evaluate on which side the equilibrium for reaction 54 lies. Because we subsequently considered the thermochemistry of sulphonyl sulphenates, we can now provide a partial, but admittedly long-winded, answer for the Ar = Ph species (46). The reader is reminded that A Hf(g, 46) — 52 kcal mol 1 and of the finding of Turecek and coworkers34 that the heat of formation of gaseous benzenesulphenic acid (84) is —8 kcal mol-1. Likewise, the reader may recall from Section VII.D our estimation for solid benzenesulphonic acid that AH (s, 20) = — 117 kcal mol- L These data cannot be immediately combined because of the discrepancy in the state for which the three species other than H20 are known. Do we wish to consider condensed phase species, in which case we need the sublimation energy of the sulphonyl sulphenate 46 and the sulphenic acid 84, or to consider gas phase species, in which case we need the sublimation energy of the sulphonic acid 20 ... 

We will now assume all of the species in reaction 55 are in their condensed phases and again fail to distinguish heats of vaporization and sublimation. For the sulphonyl sulphenate 46, we again use equation 47 where the ncessary value of b was derived as the sum of those for sulphones, ethers and sulphides, resulting in a predicted AHf(g, 46) value of —83 kcal mol-1. Relatedly, the value of b for sulphenic acids was taken as the sum of those for alcohols and sulphides, and thus AHf(g, 85)= —26 kcal mol-1. The left-hand side of reaction 39 is [ — 117 + ( — 26)] — [ — 83 +( — 68)] = 8 kcal mol-1 more stable than the right, where we remember that the value for PhS02—O—S—Ph is an upper bound. The results for the gaseous and condensed phases are thus seen as consonant. It is safe to say that benzenesulphonyl benzenesulfenate is best not viewed as an anhydride since its hydrolysis is endothermic. 

Schenone and coworkers have shown in a large number of papers that tertiary aminomethyleneketones react as heterodienes, e.g. with sulphene generated from aliphatic sulphonyl chlorides and triethylamine as a heterodienophile, to yield / -aminosultons in a Diels-Alder reaction. An early simple example is reported by Opitz270 (equation 199). 

The presence of a second tertiary amine group can result in further complications owing to competition with the neighbouring enamine function for the electrophilic sulphene204 (Scheme 88). Aromatic sulphonyl chlorides cannot form sulphenes and hence give the acyclic sulphone205-207 (Scheme 89). 

Calculations227 indicate thatthese intermediates have very similar HOMO and LUMO energies and that their LUMO coefficients are very similar to each other so we cannot look to these features to explain the striking difference in the reactivity of these two species. The former (252) cannot be isolated when sulphonyl chlorides are treated with base instead the intermediate sulphene (e.g. 254) rapidly dimerizes.228 By contrast, sulphines (e.g. 255 and 256) are an easily isolated class of compound.226,229 The same... 

Sulphonyl halides, most commonly the chlorides, may also be converted into sulphonic acids via a route involving sulphenes. Normally, sulphene is formed by reaction of a sulphonyl chloride, which possesses an a-hydrogen atom, with a tertiary amine as shown in equation 62. There are, however, many other routes by which sulphenes may be formed and these have been reviewed previously305. The intermediate sulphene then reacts with water to give the sulphonic acid. If D20 is used, then a deuterated sulphonic acid is produced306-310, as indicated by equation 63. 

Reaction of sulphonyl halides, that contain an a-hydrogen atom, with tertiary amine bases, under anhydrous conditions, usually occurs via a reactive sulphene intermediate. 

These reactions have been discussed in the excellent review of King305. This reaction proceeds best at temperatures of — 20 to — 40 °C, since oligomerization of sulphene is a problem at higher temperatures. It should be noted that sulphene, generated by methods other than from the sulphonyl chloride, also reacts with alcohols to give sulphonate esters305,374. 

Earlier, it was shown that sulphenes, formed by reaction of sulphonyl halides with a base, reacted with alcohols to give sulphonate esters. These same reactive intermediates have also been used for the formation of sultones, by reaction with carbonyl-containing compounds424-428, as shown in equation 98. If the carbonyl compound contains an a-... 

The reaction of a sulphonyl chloride with amines to produce a sulphonamide also occurs in the presence of a base305,307,482,483. In this case, it is well established that the reaction proceeds via a sulphene intermediate, as shown in equation 117. Using this method for the preparation, some novel sulphonamides may be obtained. Thus, the reaction of sulphene with phthalimide give iV-methylsulphonylphthalimide484,485, as shown in equation 118. Reaction of sulphene with pyridine leads to a novel cyclic... 

On the other hand, for the five-membered sultone, although the benzylic proton is labile and the phenoxide ion is a good leaving group, the ElcB mechanism is suppressed because the transition state 45 for this reaction would lead to the high-energy perpendicular sulphene. It seems reasonable to conclude therefore that the difference in reactivity of sultones and phenyl benzenesulphonate, which does not possess a potential carbanion centre, reflect differences in rate of attack at sulphonyl sulphur in cyclic and acyclic esters. 

Sulphenes (59), generated from the reaction of sulphonate esters or sulphonyl chlorides with triethylamine, react with triphenylphosphine to form phosphonium salts. ... 

Continuation of studies aimed at preparing sulphenes by pyrolysis of sulphonyl derivatives has involved the allyl vinyl sulphone (134), which on heating at 170 °C in the liquid phase, or at 800 °C in the gas phase, gives products derived from the sulphene, itself arising through a sulpho-Cope [3,3]sigmatropic rearrangement. ... 

Sulphonyl Halides and Sulphenes.—It is becoming clear that reactions of alkanesulphonyl chlorides in the presence of a tertiary amine are likely to give poor yields of simple sulphonation products, due to the formation of sulphenes (RCHaSOgCl RCH=SOa) and artefacts resulting from them. Electron-withdrawing groups in the substituent facilitate sulphene... 

The most common route to sulphenes, the elimination of hydrogen halide from a sulphonyl halide, has been the subject of a recent mechanistic and kinetic study which led to the conclusion that this reaction most probably proceeds by an El mechanism. Tsuge and Iwanami used this reaction for the generation of benzoylsulphene (130) from benzoylmethane-sulphonyl chloride. The reaction of (130) with a series of anils (131) was found to be somewhat dependent on the presence or absence of triethylamine and very dependent on the nature of R in (131). For R = alkyl, the (4 -I- 2) cycloadduct (132) is the predominant or only product, whereas for R = aryl the (2 + 2) cycloadduct (133) is the reaction product. Similar results were obtained for the reaction of (130) with carbodi-imides. The reaction of (130) with aryl cinnamylideneamines gave Diels-Alder adducts (134). ... 

Formation.—Preparation of thietan oxides by oxidation of thietans is covered in the previous section. Cycloaddition of sulphenes to electron-rich alkenes, the other important method of preparation of episulphones, has been further used for the preparation of a-chloro- and /S-amino-, cf-sila- and -amino-, and cf-alkoxycarbonyl- and -amino-thietan dioxides. The sulphonyl enamine (96) can be converted into the thietan dioxide (97) by treatment with acid, a procedure that usually hydrolyses enamines to ketones. Regeneration of (96) from (97) occurs on heating in alcoholic base. Thiet sulphone cyclo-adds to cyclopentadiene to give the Diels-Alder adducts with an exo/endo ratio of 0.25. ... 

The perhalogenoketones(CF2Cl) CX>, (CFCl2)2CO, and(CF a)(CFCl,)CO undergo cycloaddition with sulphene, generated in situ from methane-sulphonyl chloride and triethylamine, to yield jS-sultones in 60—81% yield. However, under comparable conditions the alkyl perfiuoroalkyl ketones MeCO CF, and EtCO CQF yield vinyl sulphonates, - e.g. 

The reactions of sulphimides studied recently concern the kinetics of the reaction between PhSH and JV-toluene-p-sulphonyl-sulphimides - to give PhSSPh, or RSPh (other differences exist between the results from these two studies) the formation of vinyl sulphides by treatment of JV-toluene-p-sulphonyl aryl ethyl sulphimides with Bu OK [TsN=S(Et)Ar -> CHg= CHSAr] the halide-ion-induced Stevens-type rearrangement to the sulphen-amide [TsN=SRAr -> RN(Ts)SAr] and the S-substitution or Pummerer rearrangement products from iV-toluene-/j-sulphonyl-sulphimides by cleavage with NaOH or NaOMe in MeOH. °... 

Sulphonylamines and Sulphurtri-imides.—As analogues of sulphenes, sulphonyl-amines were generated from chlorosulphonylamines and triethylamine to give, e.g., (38) as an intermediate, which could be added to a diazoalkane to yield a... 

The extrusion of sulphur dioxide from a sulphene to give a carbene has been postulated previously, but never authenticated. Flash pyrolysis of a-(toluene-p-sulphonyl)phenyldiazomethane gave i7-tolyl phenyl ketone (15%) and 2-methylfluorene (5%). The former could arise from phenyl-p-tolylsulphene by loss of sulphur monoxide and the latter by loss of sulphur dioxide to give the carbene, which rearranges to the fluorene. Sulphene is postulated as an intermediate in the formation of carbonyl sulphide by the solid-state photolysis of dimethyl sulphone and by various other high-energy processes. 

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