Silanethiols acidity

These results were said to be consistent with efficient (p-d)7r bonding in the silanethiols, as in the silanols. The high Bronsted acidity of silanethiols was postulated to be due to increased 7r-bonding in the silanethiolate anions relative to the parent silanethiols. 

Examples of application of the iert-dodecanethiol/silane couple include typical reductive dehalogenations, but also Barton-McCombie deoxygenations of alcohols, through conversion of the latter into xanthate esters (eq 6), hydrosilylations of alkenes (eq 7), and preparation of silanethiols. The thiol can also be used as a polarity reversal catalyst in conjunction with tris(trimethylsilyl)silane and hexabutyldistannane/malonic acid. ... 

When heated to 125 °C in a hydrocarbon solvent in the presence of a thiol as the catalyst and DBPB as initiator, the c/s-cyclic ketal 7 underwent selective epimerization at the C-H center a to oxygen to give the thermodynamically more stable trans-epimer 8. Silanethiols were found to be more effective protic-polarity reversal catalysts than alkanethiols (eq 4). Thus, in the presence of TBST and a small amount of collidine as the scavenger of adventitious acid formed under the reaction conditions, the epimerization of 7 proceeded smoothly to give 8 in 84% conversion after 1 h. Interestingly, when triphenylsilanethiol was used as the catalyst, the coadministration of collidine proved to be detrimental, resulting in a suppression of the isomerization. This is probably because this latter thiol is susceptible to nucleophilic attack by the base. The improved performance of TBST is therefore attributed to its stability toward nucleophilic substitution at the silicon center. 

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