214768-77-1Relevant academic research and scientific papers
Carbohydrate-derived thiols as protic polarity-reversal catalysts for enantioselective radical-chain reactions
Cai, Yudong,Roberts, Brian P.,Tocher, Derek A.
, p. 1376 - 1386 (2007/10/03)
A variety of novel homochiral carbohydrate-derived thiols, in which the SH group is attached to the anomeric carbon atom, have been prepared and characterised. These thiols have been evaluated as protic polarity-reversal catalysts to mediate the enantiose
Enantioselective radical-chain hydrosilylation of alkenes using homochiral thiols as polarity-reversal catalysts
Haque, M. Bodrul,Roberts, Brian P.,Tocher, Derek A.
, p. 2881 - 2889 (2007/10/03)
The thiol-catalysed radical-chain additions of triphenylsilane and of tris(trimethylsilyl)silane to a number of cyclic prochiral terminal alkenes have been carried out at 60°C in the presence of di-tert-butyl hyponitrite as initiator. The function of the thiol catalyst is to promote the overall abstraction of hydrogen from the silane by the nucleophilic carbon-centred radical intermediate, formed by addition of the silyl radical to the alkene, and the stereogenic centre in the final adduct is set by hydrogen-atom transfer from the thiol to this β-silylalkyl radical. When the thiol is homochiral the transfer of hydrogen becomes enantioselective and an optically active adduct results. A number of homochiral thiols were investigated and the highest enantiomeric excesses (up to 95%) were achieved using the tetra-O-acetyl derivatives of 1-thio-β-D-glucopyranose and 1-thio-β-D-mannopyranose. The absolute configuration of an enantiopure triphenylsilane adduct (upgraded by recrystallisation) was determined by X-ray crystallography and it was shown that this adduct could be oxidatively desilylated to the corresponding alcohol and acetate with no loss of enantiomeric purity.
