Dimethylsulfonium ylids

Aldehydes and ketones can be converted to epoxides in good yields with the sulfur ylids dimethyloxosulfonium methylid (60) and dimethylsulfonium methylid (61). For most purposes, 60 is the reagent of choice, because 61 is much less... 

Dimethyl sulfide is a useful precursor to sulfur ylids, reacting with iodomethane to give trimethylsulfonium iodide (609). When this salt was treated with n-butyllithium, deprotonation of the hydrogen on the a-carbon led to dimethylsulfonium methylid (610). Dimethyl sulfoxide also reacts with alkyl halides to give a sulfoxonium salt. When DMSO reacted with iodomethane, trimethylsulfoxonium iodide (611) was formed. As with the dimethyl sulfide derivative, treatment with a strong base such as -butyllithium generated the corresponding ylid, dimethylsulfoxonium methylid (612). 

Another difference in the reactivity of these two ylids is reflected in their reactions with a, 3-unsaturated ketones. The carboethoxy dimethylsulfonium methylid 620 reacted with cyclohexenone to give the usual alkoxy sulfonium salt 621. Intramolecular displacement of dimethyl sulfide led to the expected oxirane (622) analogous to the formation of 614. Dialkylsulfonium ylids react via 1,2-addition with displacement of the... 

SchlieBlich vermag auch ein weiterer Sulfonium-Substituent ein Sul-foniumylid zu stabilisieren. Bis-dimethylsulfonium-methan ergibt mit Natronlauge ein reaktionstrages Ylid (105). Mit Benzoylchlorid, gefolgt von Wasser, entsteht daraus u.a. Phenyl-glyoxalhydrat (66). 

The reaction of an aldehyde with a phosphorus ylid was noted several times in previous sections. Sulfur ylids such as dimethylsulfonium methylid used here also react with aldehydes, in this case with 5.81, to give an epoxide. Subsequent opening... 

A polymeric sulfur ylid reagent containing dimethylsulfonium methylide was synthesized by Tanimoto et al. (1967) from a copolymer of p-vinylphenylmethyl thioether, styrene, and DVB, according to Scheme 12-17. The reagent was used for the synthesis of epoxides from the carbonyl compounds. It was claimed that, in addition to simplifying the procedure for isolation of the products, the polymeric reagent is nonodorous and convenient to handle, compared to the noxious, volatile, low-molecular-weight sulfides used in classical syntheses. 

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