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Sulphonium ylides reactions

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. [Pg.187]

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" ". ... [Pg.668]

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... [Pg.670]

Ylides may react with nitrosobenzene in a similar fashion to their reactions with carbonyl compounds (equation 12). Sulphonium ylides give nitrones phosphonium... [Pg.671]

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. [Pg.400]

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. [Pg.26]

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]. [Pg.50]

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],... [Pg.316]

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. [Pg.23]

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... [Pg.289]

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... [Pg.296]

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... [Pg.297]

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... [Pg.298]

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... [Pg.298]

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... [Pg.302]

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... [Pg.302]

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... [Pg.303]

Azides react with sulphonium ylides, but the course of the reaction varies with the structure of the ylide. Dimethylsulphoniumphenacylide reacted with aryl azides to afford enamines (53) and with ethyl azidoformate to give (54). Dimethylsulphonium-methoxycarbonylmethylide with aryl azides led to a mixture of three products, the diazo-compound (55) being readily converted into the enamine corresponding to (53). ... [Pg.305]

Hortmann and Harris have reported further information on the reaction of dimethyloxysulphonium-methylide with a-keto-alkynes. Under certain conditions the initial adduct (69) could be isolated, but at higher temperatures the 1-methylthiabenzene 1-oxide (70) was obtained. The adduct (69) could be converted into (70) by heating in chloroform or by treating with ethanolic sodium ethoxide. Tamura et al. have reported an X-iay crystallographic analysis of one such structure which had C—S (ring) bond lengths of 1.706 and 1.696 A, lengths very similar to those of other sulphonium ylides. Treatment of (70 = R = Ph) with n-butyl-... [Pg.311]

Becker and Gosselck have reported the addition of sulphonyl carbanions to dimethylvinylsulphonium ion to give cyclopropanes. Interestingly, the sulphinate ion was not displaced in these reactions. Instead, the initial adduct (83) underwent a proton transfer, converting a sulphonium ylide into a sulphonyl ylide, and the latter apparently... [Pg.317]

Few new reactions of sulphoximines have been reported, other than their use in being converted into sulphonium ylides, a reaction and process which is discussed below. Two groups have separately reported the reaction of imino-oxydimethylsulphurane, MeaS(0)=NH, as a nucleophile in reactions with active halides, particularly inorganic halides such as SF and BrFaPO. It seems safe to conclude that the imine proton is as replaceable in the sulphoximines as it is in the iminosulphuranes. [Pg.330]

Reactions.—In Volume 5 (p. 74), an example of the formation and alkylation of a sulphonium ylide anion was given. Another example (4) has now been described, ... [Pg.81]

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... [Pg.83]

Intramolecular reactions of sulphonium ylides, generated from sulphonium salts of type (139), provide access to bicyclic epoxides (X = and... [Pg.252]

Considerable attention has been focussed recently upon the reaction of car-benes with sulphur compounds, and there are now many examples of stable sulphonium ylides. The first example of a rearrangement within this series has been reported by Benati et aL, with formation of the dibenzothiepin (251). [Pg.394]

Acyl and 2-aroyl-2,3-dihydrobenzofurans are easily prepared by the addition of carbonyl-stabilized sulphonium ylides to o-hydroxybenzyl alcohols or quater-nized Mannich bases (Scheme 19) the reactions take place at room temperature. [Pg.208]


See other pages where Sulphonium ylides reactions is mentioned: [Pg.380]    [Pg.380]    [Pg.672]    [Pg.672]    [Pg.4]    [Pg.11]    [Pg.166]    [Pg.252]    [Pg.289]    [Pg.294]    [Pg.298]    [Pg.299]    [Pg.306]    [Pg.328]    [Pg.81]    [Pg.82]    [Pg.82]    [Pg.84]    [Pg.164]    [Pg.104]   
See also in sourсe #XX -- [ Pg.21 ]

See also in sourсe #XX -- [ Pg.21 ]

See also in sourсe #XX -- [ Pg.21 ]




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Reactions of Sulphonium Ylides

Sulphonium ylide

Sulphonium ylides

Ylide reaction

Ylides reaction

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