Carbon-13 NMR spectroscopic determination of the magnitude of the .beta.-silyl stabilization effect in 1-mesitylvinyl cations

Siehl, Hans Ullrich; Kaufmann, Frank Peter

doi:10.1021/ja00038a088

Cited by 66 publications

(15 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…First noticed by Ushakov and Itenberg in 1937, Sommer and co-workers reported the particular high reactivity of β-chlorosilyl compounds in elimination reactions. , Since then, the β-silicon effect has become one of the text book examples for activating and directing effects in synthetic chemistry . In the early 1990s, β-silyl-substituted carbocations were prepared and characterized by NMR spectroscopy at low temperatures in superacidic media. − However, the unavoidable presence of fluoride under these reaction conditions led to the fast desilylation of the produced cations at temperatures above −100 °C. In this regard, the particularly non-nucleophilic and fluoride-free reactions conditions which are crucial for the synthesis of silylium ions are also beneficial for the isolation and characterization of silyl-stabilized carbocations.…”

Section: Applications Of Silylium Ions In Synthesis and Catalysismentioning

confidence: 99%

Silylium Ions: From Elusive Reactive Intermediates to Potent Catalysts

et al. 2021

View full text Add to dashboard Cite

The history of silyl cations has all the makings of a drama but with a happy ending. Being considered reactive intermediates impossible to isolate in the condensed phase for decades, their actual characterization in solution and later in solid state did only fuel the discussion about their existence and initially created a lot of controversy. This perception has completely changed today, and silyl cations and their donor-stabilized congeners are now widely accepted compounds with promising use in synthetic chemistry. This review provides a comprehensive summary of the fundamental facts and principles of the chemistry of silyl cations, including reliable ways of their preparation as well as their physical and chemical properties. The striking features of silyl cations are their enormous electrophilicity and as such reactivity as super Lewis acids as well as fluorophilicity. Known applications rely on silyl cations as reactants, stoichiometric reagents, and promoters where the reaction success is based on their steady regeneration over the course of the reaction. Silyl cations can even be discrete catalysts, thereby opening the next chapter of their way into the toolbox of synthetic methodology.

show abstract

Section: Applications Of Silylium Ions In Synthesis and Catalysismentioning

confidence: 99%

Silylium Ions: From Elusive Reactive Intermediates to Potent Catalysts

et al. 2021

View full text Add to dashboard Cite

show abstract

“…First, formationo fb oracyclohexadiene is kinetically much more favourable than formationo fb orepin, which is ascribed to the facile 1,2-silyl migration and high stability of the intermediate 2gS as ar esult of the b-silyl effect. [14] Second, the stabilities of borepin 1gSBP and boracyclohexadiene 1gSCD are very poor due to the presence of very bulky silyl substituents.…”

Section: Reactionsofb Orafluorenementioning

confidence: 99%

DFT Studies on the Reactions of Boroles with Alkynes

Wang

Zhou

Zhang

et al. 2018

Chemistry A European J

View full text Add to dashboard Cite

DFT calculations were performed to investigate the reactions of boroles with alkynes, in which boranorbornadiene, borepin and/or boracyclohexadiene can be formed depending on the substituents on the borole and alkyne. Our computational results indicated that formation of boranorbornadiene and borepin is generally kinetically favoured and that the products can interconvert. Formation of boracyclohexadiene is kinetically unfavourable in most reactions. However, certain substituents can promote the formation of boracyclohexadiene by stabilizing an energetically high-lying zwitterionic transition state that leads to boracyclohexadiene. Borafluorene reacted with most alkynes to give borepin exclusively due to its propensity to maintain its aromaticity. However, when it reacted with silyl-substituted alkyne(s), a novel product, different from boranorbornadiene, borepin and boracyclohexadiene was generated, which can be attributed to the well-known ability of silyl groups to migrate.

show abstract

“…These reactions were postulated to involve generation of reactive vinyl-like cations via protonation of carbon atom at the triple bond. In 1992, Siehl et al [9] were the first to detect arylvinyl cations as kinetically independent species in the system HSO 3 F-SbF 5 and characterize them by 1 H and 13 C NMR spectra. Analysis of the available experimental data shows that the chemistry of acetylenic compounds in superacids still remains an unexplored area of organic chemistry.…”

mentioning

confidence: 99%

Protonation and cyclization of 1,3-diarylpropynones in superacids

Васильев

Walspurger²,

Pale³

et al. 2004

Russ J Org Chem

View full text Add to dashboard Cite

1,3-Diarylpropynones ArC≡CCOAr' in superacids with H 0 ranging from -20 to -14 undergo protonation at the carbonyl oxygen atoms to give stable ArC≡CC(O + H)Ar' ions or at the acetylenic C 2 atom with formation of reactive ArC + =CHCOAr' species. The effects of the Ar and Ar' substituents and reaction conditions on the intramolecular cyclization of ArC + =CHCOAr' to 3-arylinden-1-ones are discussed.

show abstract

Carbon-13 NMR spectroscopic determination of the magnitude of the .beta.-silyl stabilization effect in 1-mesitylvinyl cations

Cited by 66 publications

References 0 publications

Silylium Ions: From Elusive Reactive Intermediates to Potent Catalysts

Silylium Ions: From Elusive Reactive Intermediates to Potent Catalysts

DFT Studies on the Reactions of Boroles with Alkynes

Protonation and cyclization of 1,3-diarylpropynones in superacids

Contact Info

Product

Resources

About