Derivate des Imidazols, XIII. Carben‐Komplexe des Siliciums und Zinns

Kühn, Norbert; Kratz, Thomas; Bläser, Dieter; Boese, Roland

doi:10.1002/cber.19951280307

Cited by 195 publications

(172 citation statements)

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“…The ClSi-Cl angle of 176.3(1) • in 1 indicates a slight distortion of the trigonal-bipyramidal geometry. Owing to the steric demand of the isopropyl substituents in [14,16]. In contrast, the Si-Cl bonds (227.03(6) pm) in 1 are longer than the Si-Cl axial bonds in the (NHC)SiCl 4 system (219 -222 pm [14,16]).…”

Section: Resultsmentioning

confidence: 99%

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Coordination of N-Heterocyclic Carbene to H₂SiX₂ (X = Cl, OTf) and H₃SiOTf (OTf = OSO₂CF₃): Synthesis of Donor-stabilized Parent Silylium Salts with Four- and Five-coordinate Silicon Atoms

Xiong

Yao

Drieß

2013

Zeitschrift Für Naturforschung B

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The reactivity of the N-heterocyclic carbene (NHC) 1,3-bis (2,6-diisopropylphenyl) (5); the latter represent the first NHC adducts of the parent silylium cation (H 3 Si + ). The multinuclear NMR and IR spectroscopic data of the products reflect the characteristics of four-, five-, and six-coordinate silane complexes. All new compounds were structurally characterized by single-crystal X-ray diffraction analyses.

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Section: Resultsmentioning

confidence: 99%

“…Owing to the steric demand of the isopropyl substituents in [14,16]. In contrast, the Si-Cl bonds (227.03(6) pm) in 1 are longer than the Si-Cl axial bonds in the (NHC)SiCl 4 system (219 -222 pm [14,16]). Single crystals of 2 suitable for X-ray diffraction analysis have been obtained from hexane solutions at ambient temperature.…”

Section: Resultsmentioning

confidence: 99%

Coordination of N-Heterocyclic Carbene to H₂SiX₂ (X = Cl, OTf) and H₃SiOTf (OTf = OSO₂CF₃): Synthesis of Donor-stabilized Parent Silylium Salts with Four- and Five-coordinate Silicon Atoms

Xiong

Yao

Drieß

2013

Zeitschrift Für Naturforschung B

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“…Eric Rivard (University of Alberta, Edmonton, Canada) summarizes this emerging new field from the point of view of low valent silicon chemistry in chapter titled "Recent Advances in the Heterocyclic Carbene-Supported Chemistry of Silicon" of Volume 2. Interestingly, however, N-heterocyclic carbenes were initially employed by Kuhn et al for the expansion of the coordination sphere of molecular silicon compounds beyond the usual four substituents [8]. Since it is now well established that this expansion does not entail hypervalency, low valent compounds with higher coordination numbers are one possible approach to increase the functionality of hypercoordinate silicon species.…”

Section: Prefacementioning

confidence: 99%

Functional Molecular Silicon Compounds II

2014

Structure and Bonding

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“…18 Support for this pathway includes the known interaction of TMSI as well as polychlorosilanes with N-heterocyclic carbenes to form stable adducts. 19 However, these experiments by Kuhn involved less sterically encumbered carbenes than 2.A second possible mode of reactivity is an NHC-initiated reaction in which the N-heterocyclic carbene interacts with the aldehyde and not the silyloxy compound. A clear possibility based on the known interactions of N-heterocyclic carbenes with aldehydes 13 is the initial addition of the nucleophilic NHC 2 to the aldehyde to form an alkoxide intermediate 14 devoid of an We lend support for the latter NHC-initiated mechanism with the isolation and X-ray structure of the N-heterocyclic carbene-aldehyde adduct (Figure 2).…”

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confidence: 99%

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N-Heterocyclic Carbene-Initiated α-Acylvinyl Anion Reactivity: Additions of α-Hydroxypropargylsilanes to Aldehydes

2007

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Highly substituted α,β-unsaturated ketones are prepared by the N-heterocyclic carbene-initiated addition of α-hydroxypropargylsilanes to aldehydes. This strategy serves as a highly efficient alternative to the standard Morita-Baylis-Hillman (MBH) approaches for these types of compounds. In contrast to the MBH reaction, different substitution in the β-position of the product (R 1 ) can be accommodated in moderate to excellent yields with a high degree of control over the resulting alkene.The Morita-Baylis-Hillman (MBH) reaction is an efficient reaction that generates highly functionalized compounds by employing α-acylvinyl anion reactivity. 1 Significant advances in the MBH reaction have been made recently, including mechanistic studies as well as asymmetric and intramolecular variants. 2,3 Despite this progress, the intermolecular MBH reaction has intrinsic limitations. In particular, the β-substituents of the activated alkene starting materials (e.g., ethyl acrylate, vinyl ketones) are almost always hydrogen atoms. Recently, we reported the scandium(III)-catalyzed addition of silyloxyallenes to aldehydes as a valuable alternative to the MBH and other α-acylvinyl anion processes (Option I, Figure 1). 4-6 These reactions proceed under very mild conditions (10 mol % Sc(OTf) 3 ) and accommodate a wide scope of β-substitution with excellent yields and a high degree of control over the resulting alkene geometry. Also, enantioenriched products could be synthesized by the (-)-(salen)Cr (III)-catalyzed additon of racemic silyloxyallenes. 4 One aspect of the transformation is the prerequisite of preparing the silyloxyallenes in a separate step through the Kuwajima-Reich rearrangement of the α-hydroxypropargylsilane precursors. 7 Herein, we present an alternative single-flask approach starting directly from the propargylsilanes, thus further enhancing the applicability of this unconventional α-acylvinyl addition reaction (Option II, Figure 1).Our current interests include the development of reactions employing Lewis base activation to efficiently access unconventional reactivity. Several transformations from our laboratory, including acyl anion additions, homoenolate reactions, alkyne additions, disilylations of activated alkenes, and hydroacylations of ketones have been facilitated by the use of Lewis bases. 8 Given our strong interest in the combination of Lewis basic promoters/catalysts, we reasoned that Lewis bases may activate silyloxyallenes toward addition. In particular, they scheidt@northwestern.edu. Supporting Information Available: Experimental procedures and spectral data for all new compounds, and a CIF file for H14·Cl. This material is available free of charge via the Internet at http://pubs.acs.org. should be more compatible with the rearrangement conditions (substoichiometric n-BuLi, THF) of the α-hydroxypropargylsilanes to the allenes and facilitate a single flask procedure. NIH Public AccessStarting with α-hydroxypropargylsilane 1 in THF at 0 °C, the allene was formed with use of 5 mol % of n-B...

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Derivate des Imidazols, XIII. Carben‐Komplexe des Siliciums und Zinns

Abstract: Stable adducts of the composition L . SiC14 (2), L . SiR2C12 (3, 4), and L . SnR2C12 (6) are formed by the reaction of the imidazol-2-ylidenes L (1) with the corresponding silicon and tin

Cited by 195 publications

References 39 publications

Coordination of N-Heterocyclic Carbene to H₂SiX₂ (X = Cl, OTf) and H₃SiOTf (OTf = OSO₂CF₃): Synthesis of Donor-stabilized Parent Silylium Salts with Four- and Five-coordinate Silicon Atoms

Coordination of N-Heterocyclic Carbene to H₂SiX₂ (X = Cl, OTf) and H₃SiOTf (OTf = OSO₂CF₃): Synthesis of Donor-stabilized Parent Silylium Salts with Four- and Five-coordinate Silicon Atoms

Functional Molecular Silicon Compounds II

N-Heterocyclic Carbene-Initiated α-Acylvinyl Anion Reactivity: Additions of α-Hydroxypropargylsilanes to Aldehydes

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Derivate des Imidazols, XIII. Carben‐Komplexe des Siliciums und Zinns

Abstract: Stable adducts of the composition L . SiC14 (2), L . SiR2C12 (3, 4), and L . SnR2C12 (6) are formed by the reaction of the imidazol-2-ylidenes L (1) with the corresponding silicon and tin

Cited by 195 publications

References 39 publications

Coordination of N-Heterocyclic Carbene to H2SiX2 (X = Cl, OTf) and H3SiOTf (OTf = OSO2CF3): Synthesis of Donor-stabilized Parent Silylium Salts with Four- and Five-coordinate Silicon Atoms

Coordination of N-Heterocyclic Carbene to H2SiX2 (X = Cl, OTf) and H3SiOTf (OTf = OSO2CF3): Synthesis of Donor-stabilized Parent Silylium Salts with Four- and Five-coordinate Silicon Atoms

Functional Molecular Silicon Compounds II

N-Heterocyclic Carbene-Initiated α-Acylvinyl Anion Reactivity: Additions of α-Hydroxypropargylsilanes to Aldehydes

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Coordination of N-Heterocyclic Carbene to H₂SiX₂ (X = Cl, OTf) and H₃SiOTf (OTf = OSO₂CF₃): Synthesis of Donor-stabilized Parent Silylium Salts with Four- and Five-coordinate Silicon Atoms

Coordination of N-Heterocyclic Carbene to H₂SiX₂ (X = Cl, OTf) and H₃SiOTf (OTf = OSO₂CF₃): Synthesis of Donor-stabilized Parent Silylium Salts with Four- and Five-coordinate Silicon Atoms