Trimethylsulfoxonium halides

Base-catalyzed proton abstraction from trimethylsulfoxonium halides (1) with formation of dimethylsufoxonium methylide (2) was described by Corey in 1962. Solutions of (2) in dimethyl sulfoxide are conveniently prepared from the chloride or iodide (1) by stirring with one equivalent of sodium hydride at room temperature. 

Methyl-l,2,4-triazines 5 are obtained when 5-chloro-l,2,4-triazines are reacted with trimethylsulfoxonium halide and a base, followed by workup with deactivated Raney nickel.185 5-Alkyl-1,2,4-triazines 6 are obtained by reaction of 5-chloro-l,2,4-triazines with ethylidene-triphcnyl-/.5-phosphanes and aqueous workup.185... 

With strong bases it is also possible to remove a proton from the methyl group of triarylmethylphosphonium halides, trimethylsulfonium iodide, or trimethylsulfoxonium iodide (Figure 9.1). Here, too, species are produced that are betaines of the ylide type. 

Methylation of DMSO with methyl iodide yields trimethylsulfoxonium iodide (Scheme 14). This is an unusual reaction since other sulfoxides and halides form the products of O-alkylation. By treatment with strong bases, the trimethylsulfoxonium salt is converted into the sulfoxonium ylide (25) (Scheme 14). 

N-Trim ylsilylacetamide, 1232,1235-1236 Trimethylsilyl azide, 1236 l-Triiiiethylsilyl-l,4-dihydropyridine, 1235 O-Trimethylsilyl ethers, 427 Trimethylsulfonium halides, 314, 315 Trimethylsulfonium iodide, 1236 Trimethylsulfoxonium iodide, 1236... 

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). 

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