The Lewis acidity of several aryl-substituted tetrylium ions was classified experimentally by applying the Gutmann-Beckett method and computationally by calculation Of fluoride ion affinities (FIA) (tetrel elements = Si, Ge). According to these measures, tetrylium ions are significantly more Lewis acidic than boranes, and aryl-substituted silylium borates are among the strongest isolable Lewis acids. A fine-tuning of the Lewis acidity of silylium ions is possible by taking advantage of electronic and/or steric substituent effects.
Reductive Lithiation of Methyl Substituted Diarylmethylsilanes: Application to Silanediol Peptide Precursors
作者:Dácil Hernández、Rasmus Mose、Troels Skrydstrup
DOI:10.1021/ol102968g
日期:2011.2.18
Reductive lithiation of methyl-substituted diarylmethylsilanes using lithium naphthalenide represents a practical method for the preparation of the corresponding sillyl lithium reagents. Their addition to chiral sulfinimines affords versatile precursors to silanols and silanediols. The replacement of the currently used diphenylsilane motif by a more labile diarylsilane moiety allows the selective hydrolysis of one or two aryl groups by treatment with TFA.