Radical chain reduction of alkyl halides, dialkyl sulphides and O-alkyl S-methyl dithiocarbonates to alkanes by trialkylsilanes

Flight from the Tyranny of Tin: The Quest for Practical Radical Sources Free from Metal Encumbrances

“…A shrewd remedy for this problem is to include a catalytic amount of an alkanethiol, such as tertdodecanethiol (XSH), with the triethylsilane in the reaction mixture. [41] Nucleophilic alkyl radicals abstract hydrogen from thiols much more readily than from electron-rich trialkylsilanes, but the resulting electrophilic thiyl radicals abstract hydrogen from the silane more readily than the alkyl radicals. Thus, the thiol is regenerated along with the chain-carrying silyl radical, and yields of RH exceed 90 %.…”

Silyl Radicals

“…In a series of papers, Roberts and coworkers demonstrated that trialkylsilanes, in the presence of a catalytic amount of a thiol, are capable of reducing alkyl halides and other precursors (vide infra) 48,49 . On the basis of relative Si H and S H bond strengths, Roberts argued that the electrophilic thiyl radical (RS ž ) is capable of abstracting the hydrogen atom from a silane (step 2, Scheme 11) and that this reaction 'could be thermoneutral or even slightly endothermic'; this reaction might also benefit from favourable polar effects 48 …”

“…On the basis of relative Si H and S H bond strengths, Roberts argued that the electrophilic thiyl radical (RS ž ) is capable of abstracting the hydrogen atom from a silane (step 2, Scheme 11) and that this reaction 'could be thermoneutral or even slightly endothermic'; this reaction might also benefit from favourable polar effects 48 …”

Thiol Addition to the Pendant Vinylbenzene Groups of (Vinyl)polystyrene PolyHIPE Via a Batch and a Cross-Flow Method

“…[15,16] A thiol acts as a mediator of hydrogen transfer and the polyHIPE-supported thiol SH can be useful in homolytic radical reduction of alkyl halides, in the presence of a reducing silane agent, for example triethylsilane. [17] Several methods exist for the preparation of polymersupported SH, such as reduction by LiBH 4 or by hydrolysis (HCl) of thioacetate groups. We have found that the most efficient method is the aminolysis of P8 [18] (Scheme 4) leading to a loading of 0.30 mmol SH/g.…”