Steric Parameters for Substituents Bound to Atoms of Silicon and Some Other Elements of the Third Period

Ploom, Anu; Tuulmets, Ants; Järv, Jaak

doi:10.1080/10426501003713106

Cited by 3 publications

(3 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…X-ray structure analysis of catalysts ( S )- 2a – c ·HBr provides an opportunity to compare the steric volume of the silyl side chains and analyze the factors that account for the observed selectivity. − Bond lengths between the pyrrolidine carbon and silicon are approximately 1.91 Å for catalysts ( S )- 2a - c· HBr, which is 20% longer than a typical carbon–carbon bond of 1.54 Å (Table ). Using a simple geometric equation for the volume of an irregular tetrahedron, an estimate for the steric volume of the side chains on pyrrolidine was calculated (Table ) .…”

Section: Resultsmentioning

confidence: 99%

Silyl Fluoride Electrophiles for the Enantioselective Synthesis of Silylated Pyrrolidine Catalysts

et al. 2011

View full text Add to dashboard Cite

Chiral silylated pyrrolidine catalysts are obtained in high yield and enantioselectivity by sparteine-mediated lithiation of N-Boc-pyrrolidine and addition to silyl fluoride electrophiles. The activity and enantioselectivity of a new tert-butyldiphenylsilylpyrrolidine catalyst has been demonstrated for various asymmetric Michael reactions at 5 mol % catalyst loading and affords up to 99% ee for asymmetric Michael reactions with aldehydes and nitro-olefins. Acetaldehyde donors proceed with yields up to 77% and enantioselectivities up to 96% ee, avoiding common side reactions that often lower yields. Insight into the mechanism of pyrrolidine-based catalysts is provided by demonstrating ESI mass spectrometry evidence for activation of a nitro acceptor by formation of a hydrogen-bonding adduct with the catalyst amine. Analysis of reaction intermediates using mass spectrometry provides evidence that the pyrrolidine catalyst also plays a role in activating nitro-olefins through hydrogen-bonding.

show abstract

Section: Resultsmentioning

confidence: 99%

Silyl Fluoride Electrophiles for the Enantioselective Synthesis of Silylated Pyrrolidine Catalysts

et al. 2011

View full text Add to dashboard Cite

show abstract

“…7,8 Further detailed quantitative investigations 8,[13][14] established that the reaction with alkoxysilanes consists of replacement of a donor molecule at the magnesium centre by the silane followed by the subsequent rearrangement of the complex to the products through a four-centre transition state. 7,8,13,14 As alkylmagnesium chlorides exist essentially as dimeric species, which are stable over a wide concentration range, 15 the overall reaction scheme can be presented as follows:…”

Section: Introductionmentioning

confidence: 98%

“…Only a limited number of kinetic studies of the Grignard reaction with silanes have been published. [3][4][5][6][7][8][9][10][11][12][13][14] Recently, we began an extensive program for the kinetic investigation of this reaction [6][7][8][9][10][11][12][13][14] focusing, inter alia, on the mechanism of the reaction.…”

Section: Introductionmentioning

confidence: 99%

A Kinetic View of the Mechanism of the Grignard Reaction with Alkoxysilanes

Ploom

Tuulmets

Panov

et al. 2015

Phosphorus, Sulfur, and Silicon and the Related Elements

Self Cite

View full text Add to dashboard Cite

RUNNING HEAD: The Grignard reaction with alkoxysilanes ABSTRACT The kinetics of the reaction of n-butyl-and isopropylmagnesium chloride with alkyltriethoxysilanes (RSi(OEt) 3 ) in diethyl ether were determined. The rate constants correlate well with the steric parameters E s (Si). The resulting steric factors δ fit the range of available susceptibility values for the reactions of organosilicon compounds. The thermodynamic activation parameters for six reactions of ethoxysilanes with alkylmagnesium chlorides in dibutyl ether were determined. The entropy values indicated that two Grignard molecules are involved in the transition state of the reaction. From the correlation analysis of the activation enthalpies for the reactions, it appeared that the inductive effect controls the rate of replacement more considerably than steric requirements in the transition state.

show abstract

Structure-reactivity relationships in organosilicon chemistry revisited

Ploom¹,

Tuulmets

Järv

2011

Open Chemistry

View full text Add to dashboard Cite

Abstract:© Versita Sp. z o.o. Keywords: Correlation analysis • Linear free energy relationships • Silicon compounds • Substituent effectsAvailable quantitative data of the reactivity of organosilicon compounds were subjected to correlation analysis. As an alternative to the carbon chemistry values, the scale of steric constants E S (Si) can be used for organosilicon compounds and the inductive effect is best expressed by two terms, involving the parameter of electronegativity of substituents. Alkyl substituents contribute to the reactivity exclusively through their steric effects, steric and polar effects in silicon compounds are additive and the resonance effect is insignificant. The correlation analysis can be employed in investigations of organosilicon reactions along with other methods.

show abstract

Steric Parameters for Substituents Bound to Atoms of Silicon and Some Other Elements of the Third Period

Cited by 3 publications

References 18 publications

Silyl Fluoride Electrophiles for the Enantioselective Synthesis of Silylated Pyrrolidine Catalysts

Silyl Fluoride Electrophiles for the Enantioselective Synthesis of Silylated Pyrrolidine Catalysts

A Kinetic View of the Mechanism of the Grignard Reaction with Alkoxysilanes

Structure-reactivity relationships in organosilicon chemistry revisited

Contact Info

Product

Resources

About