Sulfonium iodides

Cyclopropanation of the 4,6-diene function proceeds selectively at the 5,6-double bond. Thus, reaction of 185 with the ylide from trimethyl sulfonium iodide and sodium hydride, in DMSO, affords predominantly the a-cyclopropyl compound (187) accompanied... 

P3.03.32. SODIUM ETHOXIDE AND ETHYL DIMETHYL SULFONIUM IODIDE... 

Data have been reported for the reaction at 64 C between sodium ethoxide (A) and ethyl dimethyl sulfonium iodide CB] using ethanol as a solvent. 

A weak base such as glycine added to [HMIMjPFg has also been reported to catalyze a Knoevenagel reaction of malononitrile and benzaldehyde 110). A KOH-treated [BMIMjPFg also provides a suitable medium for the Corey-Chaykovsky epoxidation of enones and cyclopropanation of aldehydes using trimethyl sulfonium iodide (///). 

Sulfonium salts of thiepanes are readily formed by electrophilic attack of alkyl halides on the cyclic thioether. Thus, thiepane (35) was found to yield a sulfonium iodide (123), which at elevated temperatures and in the presence of excess methyl iodide underwent ring cleavage to yield 1,6-diiodohexane (isolated as the 1,6-diphenoxy derivative Scheme 24) (53M1206). The alkoxysulfonium salt (124) formed by reaction of (35) with t-butyl hypochlorite (equation 23) was characterized as a stable hexachloroantimonate (67JOC2014). Reduction of thiepane 1-oxide (115) to thiepane has been achieved using an aqueous solution of NaHSC>3 (72JOC919). A hydroxysulfonium salt intermediate (125) has been proposed in the latter reduction reaction which provides a general method for sulfoxide reductions under mild conditions (equation 24). 

Chloroethyl(dimethyl)sulfonium iodide, ClCH2CH,S(CH,)2l (1). The salt, m.p. BBSS , is prepared by reaction of 2-chloroethyl methyl sulfide with CH,I. ... 

Example. The reaction of sodium ethoxide, NaOC2H6, with ethyl dimethyl sulfonium iodide, (C2H6)(CH3)2SI, in absolute ethanol solution has been shown to lead to the following products ... 

In Table IV.7 this method is applied analytically to the data on the solvolysis of dimethyl ethyl sulfonium iodide by sodium ethoxide given originally in Tabic IV.2. 

Protection of carboxyl groups (8, 94). Two new methods for deprotection of methylthiomethyl esters have been reported one involves oxidation to the sulfone followed by alkaline hydrolysis, and the other involves methylation to a sulfonium iodide and hydrolysis. ... 

Problem 23.4 When dimethyl-rer/-peniylsulfonium ethoxide is heated in ethanol, the alkene obtained is chiefly (86/J 2-methyl-l-butene when the corresponding sulfonium iodide is heated in ethanol, the alkene obtained is chiefly (86%) 2-methyl-2-butene. 

Dimethyl sulfoxide-derived reagent (b). DImethylsulfonlum methyllde, (CH S CHj. This heat-labile reagent is prepared in solution by dehydrohalogenation of trimethyl-sulfonium iodide, bromide, or perchlorate. It is an exceedingly selective methylene-... 

This precursor of dimethylsulfonium methylide is prepared in almost quantitative yield by mixing dimethyl sulfide (6 g.) and methyl iodide (14 g.). The sulfonium iodide separates as a solid cake and after 24 hrs. it is collected, crystallized from ethanol, and washed with ether. 

This reaction was also conducted with the unstable ylide derived from trimethyl-sulfonium iodide to provide an epoxide 30 in 65% yield. Then treatment with NaH in DMF at 80 °C afforded the objective compound 29 (Scheme 11). 

Dispersions of starch in dimethyl sulfoxide become stiff within 20 min when brought into contact with water.2684 Sulfonium salts can be produced by the reaction of reagents already bearing the sulfonium moiety, as when starch is treated with 2-chloroethylmethylethyl sulfonium iodide in the presence of calcium hydroxide.2685 The resulting formulations can be applied as paper coatings, paper adhesives, sizes, and thickeners.2685,2686... 

The sulfonium ylide obtained from dimethyl(trimethylsilylmethyl)sulfonium iodide by deprotonation with 1-methylpropyllithium reacts with 2-cyclohexenone to provide 7-(trimethylsilyl)-bicyclo[4.1 0]heptan-2-one with good exo selectivity10. The diastereofacial selectivity of the ylide is also high, as demonstrated by the conversion of the chiral substituted 2-cyclohexenone into cyclopropane derivative 12. 

Single crystals of these pseudo-clathrates are conveniently prepared as follows. The peralkyl salts are usually obtained by metathesis reactions between the peralkyl ammonium or sulfonium iodides and the slightly soluble corresponding silver salt taken in excess. The mixture of insoluble silver salts is removed by filtration and the supernatant (1-2 mol L ) cooled until crystals are produced. For tetraisoamylam-monium salts cooling to RT is sufficient, whereas for the tetra-n-butyl ammonium salts cooling to 5-10°C is necessary. ... 

Scheme 5.2-90 The sulfonium iodide prompted methylene addition to aldehydes [218,219].

Sulfonium salts can be converted to the corresponding sulfonium ylides promising useful reactions. Thiepane (4) reacted with methyl iodide to yield the sulfonium iodide (108) (Equation (21)) <53M1206>. Thiepanes reacted with sulfonates to give the corresponding sulfonium salts in high yields <82H(19)2147, 86CPB3644>. 

In some special cases, an isotopic dilution can occur by exchange (see Chap. 15 in Vol. 2) between the labeled reagent and the solvent or reagents used. Dimethyl sulfoxide, a commonly used solvent in alkylation reactions, might react with [ C] methyl iodide to form labeled oxo-trimethyl-sulfonium iodide. This intermediate can transfer any of the three methyl groups to... 

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