Alkyl vinyl thioethers sulfides

Thioethers (sulfides) can be prepared by treatment of alkyl halides with salts of thiols (thiolate ions).7S2 R may be alkyl or aryl. As in 0-35, RX cannot be a tertiary halide, and sulfuric and sulfonic esters can be used instead of halides. As in the Williamson reaction (0-12), yields are improved by phase-transfer catalysis.753 Instead of RS ions, thiols themselves can be used, if the reaction is run in benzene in the presence of DBU (p. 1023).754 Neopentyl bromide was converted to Me3CCH2SPh in good yield by treatment with PhS in liquid NH3 at -33°C under the influence of light.755 This probably takes place by an SrnI mechanism (see p. 648). Vinylic sulfides can be prepared by treating vinylic bromides with PhS in the presence of a nickel complex,756 and with R3SnPh in the presence of Pd(PPh3)4.757 R can be tertiary if an alcohol is the substrate, e.g,758... 

Metallation of the most simple vinyl ether H2C=CHOCH3 in the a-position has been carried out with Fbutyllithium in THF at low temperatures [81]. Ethene is deprotonated not at all by FBuLi or other strongly basic systems under the same conditions. Sec-butyllithium has been used to metallate alkyl vinyl sulfides H2C=CH—SR [82]. We found that both vinyl ethers and vinyl thioethers can be metallated with excellent results using the cheaper combination of rc-BuLi and fBuOK [9]. The cyclic vinyl ethers 2,3-dihydrofuran and 2,3-dihydropyran can be successfully metallated under the same conditions ... 

Thiols add to alkenes under photochemical conditions to form thioethers, and the reaction can be done intramolecularly to give cyclic thioethers. Thiols also add to alkynes and with a palladium catalyst, vinyl sulfides can be formed. Thio-carbonates function as thiol surrogates, converting alkenes to alkyl thiol in the presence of TiCl4 and CuO. °... 

The preparation of vinyl sulfides (or thioethers) has been extended by X-ray or irradiated addition of thiols to acetylene, and Pd(0Ac)2 or Pd(PPh3)4 catalyzed addition of thiol or disulfide to alkynes. In addition, alkyl halides (e.g., ethyl bromide, n-butyl bromide, 5 c-butyl bromide, benzyl chloride, etc.) have been successfully converted into corresponding vinyl sulfide through a one-pot process addition of acetylene mediated by thiourea. 

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