Reactions of Sulphonium Ylides

Reactions of Sulphonium Ylides.— LaRochelle et al. were unable to obtain an alkylation product from the reaction of diphenylsulphoniumallylide (6) with methyl iodide or methyl sulphate. In marked contrast, Casanova and Loewe have reported that an alkoxycarbonylide was sufficiently nucleophilic to displace chloride from picryl chloride and to effect a type of alkylation to produce a benzylide (22) which was very highly stabilized 

Mukaiyama, K. Hosoi, S. Inokuma, and T. Kumamoto, Bull. Chem. Soc. Japan, 

Fronza. G. Gaudiano, C. Ticozzi, and M. G. Zubiani, Tetrahedron, 1971, 

The bis-ylide (4) underwent C-acylation with phenyl isocyanate, but with benzoyl chloride afforded the 0-acylation product as reported for other sulphonium ylides, In the latter reaction, the initially formed sulphonium salt apparently was cleaved by the chloride ion to afford the 

Commencing with an acylation step, Mukaiyama et al utilized keten dimer to effect an annulation reaction and form the spirofuran (25). 

Normal C-acylations of sulphonium ylides with anhydrides, acyl halides, and isocyanates have been reported by several groups. However, 

Tsuge et al. found that acylation with a-ketoisocyanates, while initially affording the expected amido-ylide, presented the possibility of furth intramolecular reaction to afford an oxazole (in the case of benzoyl isocyanate) or a thiazole (in the case of thionobenzoyl isocyanate). In the latter case, the initial acylation product could not be intercepted, the thiazole being obtained, and in the former case the oxazole could be obtained by heating in decalin. 

Several groups have reported some rather unique experimental conditions for the reaction of sulphonium ylides with carbonyl compounds. Shono et al. generated the ylide in aqueous solution in the presence of 

The reaction of a substituted ylide with an aldehyde usually leads to dominant or exclusive formation of the trans-oxiran. Thus, tetra-methylenesulphoniumbenzylides reacted with substituted benzaldehydes to afford only the frans-oxirans (57). Townsend and Sharpless demonstrated that the cycle of reactions from trans-cyclodecene oxide to the hydroxysul-phonium salt (58) and back occurred with less than 3% crossover to the 

With many stabilized sulphonium ylides, their reactivity precludes 

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Kondo, K., Liu. Y, and Tunemoto, D., Preparation and reaction of sulphonium ylide stabilizes by a phosphinyl substituent, J. Chem. Soc., Perkin Trans. 1, 1279, 1974. 

The epoxide-forming reaction of sulphonium ylides with carbonyl compounds continues to be widely applied in a routine sense at the same time as new and unique applications are studied. Bravo et al. have reported that, whereas indole and dimethylsulphonium-methylide afford iV-methylindole (i.e. protonation of the ylide followed by sulphonium salt alkylation of the indole), the keto-amide (28) gives an epoxide. Similarly, the amide function in (29) did not interfere with epoxide formation. In... 

Additional examples of the reaction of sulphonium ylides with conjugated alkynes have been reported, bringing to four the courses followed in such reactions. In the first case, usually conducted in a protic solvent, addition... 

The third pattern of reaction of sulphonium ylides with alkynes results in the formation of furans. For example, the reaction which afforded (47) and (48) in benzene gave the furan (49) in high yield when DMSO was used as solvent. Furthermore, warming (47) in ethanol or DMSO effects conversion into the furan (49), perhaps indicating the actual mechanism of furan formation (i.e. enolate anion displacement of the sulphonium group). In this type of reaction, the acetylenic carbon atoms become C-3 and C-4 of... 

Other reactions of sulphonium ylides include o /9 -elimination,metal-mediated carbene-transfer to olefins, insertion into aromatic C—H bonds or other carbenoid-type processes, formation of Pd" complexes, addition to enones (forming cyclopropyl ketones or heterocycles ), reaction with isoquinoline 2-oxide, and [2,3]-sigmatropic rearrangements " [as in the case of (12) 1 or... 

Intramolecular reactions of sulphonium ylides, generated from sulphonium salts of type (139), provide access to bicyclic epoxides (X = and... 

Reactions.—The reaction of sulphonium ylides with carbonyl compounds to form oxirans is now a standard reaction. Among the more unusual examples reported are an intramolecular version directed towards the preparation of arene epoxide (12) (not isolable), the synthesis of the epoxide of 8-phenylthio-methylenecycloheptane, and the direct conversion of a diketone by dimethyl-sulphonium methylide into a doubly homologated hydroxymethyl aldehyde (13) by the rearrangement shown. ... 

A second common reaction of sulphonium ylides is Michael addition to ajS-unsaturated carbonyl compounds, giving cyclopropanes. This reaction forms the basis of a cyclopentene synthesis starting from sulphonium allylide (14). Other recent examples include the preparation of spiro[cyclopropane-l,4-A -pyrazolin]-5 -one derivatives (15) and cyclopropyl-ulose (16). Un-... 

Notable in the category of miscellaneous reactions of sulphonium ylides is the use of an ylide as a blocking group, as shown for the stable ylide (18). The hydrogenation and alkaline methanolysis of sulphonium ylides have been... 

Numerous examples have been reported of the reaction of sulphonium ylides with a 3-unsaturated carbonyl compounds whereby the ylide carbanion attacks the /3-carbon and the sulphonium group is displaced to afford a cyclopropane. Gruetzmacher reported numerous examples, and Gosselck et ai. reported ordinary addition reactions with the unusual ylides (62) and (63). The trans-isomers result from most reactions." The reaction of (64) with methyl acrylate afforded mainly the expected cyclopropane... 

Van Loock et al. have published full details of the reaction of sulphonium ylides with azides, a reaction discussed in Volume 2. ... 

Reactions of arsonium ylides with carbonyl compounds take place much more readily than with phosphonium or sulphonium ylides. The nature of the products depends upon the character of the substituents on the ylide carbon atom, where electron-withdrawing substituents favour alkene formation, and of substituents on the arsenic atom, where... 

Methods of Synthesis.—No new methodology has been reported during the past two years other than the adaptation of the sulphonium salt ligand-exchange reaction to sulphonium ylide synthesis. Trost et prepared cyclopropylidenediphenylsulphurane (1) by treatment of a triphenyl-sulphonium salt with cyclopropyl-lithium. The same ylide was prepared... 

Johnson et al have used the availability of the above reaction to study further the overall mechanism of the reaction of sulphonium and oxysul-phonium ylides with carbonyl compounds and a 3-unsaturated carbonyl compounds. The contrasts between these two types of ylides are well known and can be exemplified as follows (i) in reactions with cyclic carbonyl compounds, sulphonium ylides attack from the axial position while sulphoxonium ylides attack from the equatorial position (ii) in reactions with a/3-unsaturated ketones, sulphonium ylides react at the carbonyl group to form oxirans while sulphoxonium ylides react at the olefinic group to form cyclopropanes. These results can be explained by considering the reversibility of the initial step of each ylide reaction and whether the reaction is subject to kinetic or thermodynamic control. 

Stabilized telluronium ylides such as dibutyltelluronium carbethoxy, phenacyl/ cyano- and carbamoylmethylide (easily prepared by the reaction of dibutyl teUurides with the appropriate substituted methyl hahdes, followed by treatment with a base), undergo Wittig-type olefmation reactions with a variety of carbonyl compounds, giving the expected olefins in satisfactory yields (method A). This behaviour is in sharp contrast to that of stabilized sulphonium yhdes, which are inert towards carbonyl compounds. 

For a monograph on sulfur ylides. see Trost Melvin Sulfur Ylides Academic Press New York. 1975. For reviews, sec Fava in Bcrnardi Csizmadia Mangini Organic Sulfur Chemistry Elsevier New York. 1985, pp. 299-354 Belkin Polczhaeva Russ. Chem. Rev. 1981, 50, 481-497 Block, in Stirling The Chemistry of the Sulphonium Group, part 2. Wiley New York. 1981. pp. 680-702 Block Reactions of Organosulfur Compounds Academic Press New York. 1978. pp. 91-127. 

Sulphonium ylides are in certain cases unstable and they undergo further transformation affording useful final products. In this way allylic sulphides and selenides were used to transfer an alkylthio- or alkylseleno-group onto the a-carbon of / -dicarbonyl compounds in the form of their ylides the sequence of reactions were a transylidation followed by [2,3]-sigmatropic rearrangement. 

The reactions of a series of arsonium ylides with p-nitrobenzaldehyde have been shown to be first order for each reagent and there is a general tendency for the more basic ylides to be the more reactive" ". The correlation is not, however, complete, since factors other than basicity, e.g. steric, and interactions between ylidic substituents and the arsenic atom, also affect the reactivity " , but as a generalization it is largely valid and also must be a significant factor in the greater reactivity of arsonium compared to phosphonium and sulphonium ylides. A fair correlation has also been noted between the chemical shift of the signal from the methine proton in a series of ylides and their rates of reaction with p-nitrobenzaldehyde" ". ... 

A standard method for the preparation of arsonium and sulphonium ylides involves the reaction of an arsine oxide or a sulphoxide with a compound having an acidic methylene group in the presence of either acetic anhydride or of a mixture of triethylamine and phosphorus pentoxide. This method has been applied to a number of cyclopentadienes substituted either by phenyl groups [105,131,142] or carbonyl groups [20,142,143], When acetic anhydride is used, acetylation of the cyclopentadiene ring may also take place, e.g. 

When Z = PPh3 the intermediate salt can be isolated, when Z = SMc2 it usually cannot [88], As in other ylide reactions triphcnyl-arsonium ylides may follow the path of the phosphonium or sulphonium analogue. However a dimethylsulphonium ylide has been used to convert a tropylium salt into heptafulvene [89]. 

Reactions with Hides and Gvignard Reagents. Reaction with a phosphonium ylide or a sulphonium ylide led, respectively, to the formation of a-naphthol and an a-pyrone. In each case it was assumed that reaction proceeds xda ketene intermediates [110],... 

Further studies of carbene insertion into the C S bond are reported, the authors earlier work on alkyl allyl sulphides, using bis(methoxy-carbonyl)carbene, now being supplemented by a study of the relative tendencies towards C—S insertion and C=C addition for the same substrates with carbethoxycarbene (from ethyl diazoacetate). 1,2-Diphenyl-ethyl phenyl sulphide, PhCH(CHaPh)SPh, is formed by the action of benzyne on dibenzyl sulphide, via the sulphonium ylide. Alkylation at sulphur is one of the best-known reactions of sulphides, and novel syntheses of this type have been reported in which the formation of hydro-quinone sulphonium salts, from quinone and a sulphide in 70% H2SO4 at — 5 to -f 5 and Markownikov addition of a sulphide to an alkene under similar conditions are discussed. 

A variety of substituted sulphonium ylides have been used in the oxiran-forming reaction with carbonyl compounds. Diphenylsulphonium-allylide (6), generated from the salt with t-butyl-lithium, afforded the expected oxiran in 80% yield upon reaction with cyclohexanone. Use of n-butyl-lithium as the generating base resulted in lower yields and contamination by the oxiran formed from a butylide, the latter probably... 

Terada and Kishida have reported unusual reactions of a series of alkynyldimethylsulphonium ylides with benzaldehydes. The stabilized ylide (35) resulted from reaction of benzaldehydes with the sulphonium salt (36) in the presence of sodium hydride. Although the mechanism... 

Trost and his students have reported on the reaction of three unusual sulphonium ylides with several ajS-unsaturated ketones. The ceirboxylate-sulphonium salt (33), previously shown to react with ketones, added to tranr-benzylideneacetophenone in the presence of dimsylsodium to afford a 1 1 mixture of the isomeric cyclopropanes (42) after esterification with... 

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