Sulfonium methylides synthesis

Ring expansion of activated aziridines (43) with sulfur ylides also provides a synthesis of azetidines (75JOC2990, 58BSF345, 81CC417). The highly reactive sulfonium methylide (44 R = R = H) undergoes further reaction with the azetidines (46), but the reaction is satisfactory for substituted methylides. The less reactive sulfoxonium methylide (45 R = R = H)... 

The development of new methods for carbon-caihon bond formation is at the heart of organic synthesis. The most desirable methods are those that are easily practiced at scale, operate near ambient temperature, and that do not require strong acid or base. David C. Forbes of the University of South Alabama and Michael C. Standen of Synthetech in Albany, OR report (Organic Lett. 5 2283,2003) that the crystalline salt 2, which can be stored, smoothly converts aldehydes to epoxides, without any additional added base. The reaction is apparently proceeding by the loss of CO, from 2 to give the intermediate sulfonium methylide. 

The synthesis of lettucenin A was achieved by Monde et al. and this is described in Scheme 14. Indanone (146) was treated with dimethyl sulfonium methylide to give an aldehyde and allyl alcohol, which were... 

DesilyltUive reactions. A new version of the Peterson olefination employs a combination of ethyl trimethylsilylacetate, an aldehyde, and CsF. Similarly, epoxide synthesis from carbonyl compounds avoids strongly basic conditions by using [Ph SCHjSiMej]" TfO as a source of the sulfonium methylide. ... 

Sulfur ylides have several applications as reagents in synthesis.282 Dimethylsul-fonium methylide and dimethylsulfoxonium methylide are particularly useful.283 These sulfur ylides are prepared by deprotonation of the corresponding sulfonium salts, both of which are commercially available. 

Synthesis of racemic naproxene Friedel-Crafts acylation (aluminum chloride - nitrobenzene) of p-naphthol methyl ether affords 2-acetyl-6-methoxy naphthalene, which, when treated with either dimethyl sulfonium or dimethylsulfoxonium methylide, gives 2-(6-methoxynaphthalen-2-yl)propylene oxide. Treatment of the latter with boron trifluoride etherate in tetrahydrofuran gives 2-(6-methoxynaphthalen-2-yl)propionaldehyde, which is oxidized using Jones reagent (4 M chromic acid) to yield the racemic 2-(6-methoxynaphthalen-2-yl)propionic acid. 

Corey s procedures for the conversion of ketones into epoxides using sulfonium or oxosulfonium ylides have found widespread use in organic synthesis. An attempt to apply the method to methyl 2-benzoylbenzoate, however, gave 4-phenylisocoumarin in 52% yield when dimethyloxosulfonium methylide was used. 

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