Liberman-Martin Allegra L, Bergman Robert G, Tilley T Don
Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States.
Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 United States.
J Am Chem Soc. 2015 Apr 29;137(16):5328-31. doi: 10.1021/jacs.5b02807. Epub 2015 Apr 16.
Bis(perfluorocatecholato)silane Si(cat(F))2 was prepared, and stoichiometric binding to Lewis bases was demonstrated with fluoride, triethylphosphine oxide, and N,N'-diisopropylbenzamide. The potent Lewis acidity of Si(cat(F))2 was suggested from catalytic hydrosilylation and silylcyanation reactions with aldehydes. Mechanistic studies of hydrosilylation using an optically active silane substrate, R-(+)-methyl-(1-naphthyl)phenylsilane, proceeded with predominant stereochemical retention at silicon, consistent with a carbonyl activation pathway. The enantiospecificity was dependent on solvent and salt effects, with increasing solvent polarity or addition of NBu4BAr(F)4 leading to a diminished enantiomeric ratio. The medium effects are consistent with an ionic mechanism, wherein hydride transfer occurs prior to silicon-oxygen bond formation.
制备了双（全氟邻苯二酚）硅烷Si(cat(F))2，并通过与氟化物、三乙膦氧化物和N,N'-二异丙基苯甲酰胺的反应证明了其与路易斯碱的化学计量结合。通过与醛的催化硅氢化和硅氰化反应表明Si(cat(F))2具有较强的路易斯酸性。使用光学活性硅烷底物R-(+)-甲基-(1-萘基)苯基硅烷进行硅氢化反应的机理研究，结果表明在硅原子上主要发生立体化学保留，这与羰基活化途径一致。对映体选择性取决于溶剂和盐效应，溶剂极性增加或加入NBu4BAr(F)4会导致对映体比例降低。介质效应与离子机理一致，其中氢化物转移发生在硅-氧键形成之前。
