Thiol/thiolate ethanethiol

The first 1,6-addition reactions of thiolates to steroid dienones were examined well before the discovery of the antiestrogenic properties of 7o -substituted steroids. Ralls and coworkers129 and Djerassi and coworkers130 studied thiol additions to A3,5-steroids for example, the reaction of 3,5-cholestadien-7-one with ethanethiol was reported to proceed with high 1,6-regioselectivity and -stereoselectivity (equation 47)129. In a series of papers, Brueggemeier and coworkers131-137 described the synthesis and biochemical evaluation of numerous 7at-sul fur-substituted steroids which were prepared by Michael addition to steroid dienones. Thus, 4,6-androsta-3,17-dienone was treated with various... 

The carbon—sulphur bond is fractured in the reaction of p-toluene-sulphonyl cyanide with sodium ethanethiolate in ethanol. Other thiols, not thiolates, can also fracture the carbon—sulphur bond . ... 

Synthesis of mixed disulfides involving a methylthio unit may utilize DMTSF. Thiols and thiolates react rapidly with the reagent to yield mixed disulfides. Unfortunately, disproportionation occurs, resulting in a mixture of products. Subsequent investigations suggest that the addition of a stericaUy hindered base (eq 3), or the use of a 2-(trimethylsilyl)ethanethiol derived component (eq 4), permit high yields of unsymmetrical disulfides. 

Thiol Substitution Reactions. Vital to the usefulness of 2-(trimethylsilyl)ethanethiol is that it behaves as a typical thiol. Base mediated reactions that proceed as expected include alkylation and nucleophilic ring openings. Moreover, addition-eliminations on unsaturated systems, Michael additions, and c -additions to triple bonds (eq 2) are all routine. To access 2-(trimethylsilyl)ethyl thioethers, a useful procedure is hydrolysis of 2-(trimethylsilyl)ethyl thiolacetate and alkylation of the thiolate in a single pot. ... 

In order for the 2-(trimethylsilyl)ethylthio unit to lose its protecting group upon treatment with the fluoride, the sulfur must be attached to an unsaturated carbon. Hence the fluoride mediated sulfur deprotection is feasible for 2-(trimethyl-silyl)ethylthio substituted (het)arenes, alkenes, alkynes, and acid derivatives such as carboxylic and selenothiophosphinic acid salts. In thiolate form, the substrates have value for the formation of self-assembled monolayers or as metal complexing agents. Simple addition of acid to the thiolate to give a stable thiol characterizes 2-(trimethylsilyl)ethanethiol as a simple M" (HS) equivalent that is only capable of a single substitution reaction. ... 

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