Sodium hydrogen sulfide, reaction with alkenes

Several thiols occur naturally for example, skunk secretion contains 3-methyll-butanethiol and cut onions evolve 1-propanethiol, and the thiol group of the natural amino acid cysteine plays a vital role in the biochemistry of proteins and enzymes (see Introduction, p. 2). Primary and secondary thiols may be prepared from alkyl halides (RX) by reaction with excess sodium thiolate (SN2 nucleophilic substitution by HST) or via the Grignard reagent and reaction with sulfur. Tertiary thiols can be obtained in good yields by addition of hydrogen sulfide to a suitable alkene. Thiols can also be prepared by reduction of sulfonyl chlorides (Scheme l).la,2a... 

The Julia-Lythgoe alkenation procedure gives predominantly E-aUcene, depending on the reaction conditions. For example, oxidation of sulfide 4.55 with m-CPBA gave sul-fone 4.56, which on treatment with a base and aldehyde 4.57 followed by reduction with sodium-mercury (Na-Hg) and disodium hydrogen phosphate in MeOH afforded the E-alkene 4.58 in 68% yield. ... 

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