A New Catalytic Route for the Activation of sp-Hybridized Carbon–Hydrogen Bonds (original) (raw)
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European Journal of Organic Chemistry, 2010
The design and development of highly efficient and selective methods for the synthesis of π-conjugated arylvinyl derivatives, based on sequential catalytic reactions of organometallic reagents, have been the subject of extensive study because of their versatile application in organic synthesis and materials science. The silylative coupling of olefins with vinyl-substituted silicon compounds represents one of the most efficient and selective methods for the synthesis of alkenylsilanes, which are particularly attractive scaffolds for further [a] 219 transformations, including transition-metal-catalysed crosscoupling with organic halides or substitution with organic and inorganic electrophiles. The microreview highlights recent developments in sequential synthetic strategies including ruthenium-catalysed silylative coupling followed by desilylative cross-coupling and halogenation, leading to stereodefined organic derivatives containing arylene-vinylene units widely applied as fine chemicals, functional materials or unsaturated building blocks in organic synthesis. Scheme 1. Silylative couplings of olefins with vinylsilanes. 226 Scheme 19. Iododesilylation of 2-aryl-1,1-bis(trimethylsilyl)ethenes. Scheme 23. Application of silylative coupling in the synthesis of arylvinyl derivatives.
One-Step Preparation of Functionalized (E)-Vinylsilanes from Aldehydes
Organic Letters, 2011
Functionalized (E)-vinylsilanes have been prepared in one step from a wide range of aldehydes, via a chromium(II)-mediated olefination with novel dihalomethylsilane reagents, in moderate to excellent yields and with excellent stereoselectivity. Organosilanes are versatile functionalities in the synthetic chemist's toolbox, offering a convenient and inexpensive means to create new carbonÀcarbon 1 or carbonÀheteroatom 1b,2 bonds while remaining compatible with a range of chemical manipulations. 3 For example, vinylsilanes have been employed with great efficacy in organic synthesis, as direct mediators of carbonÀcarbon bond formation through the nucleophilic capture of cations, 1b,4 in Hiyama cross-coupling reactions, 1c,5 and also as substrates for Tamao-Fleming oxidations in which they represent masked carbonyl groups. 6 Hiyama cross-coupling in particular represents an extremely important application, which usually requires the silane to be functionalized with a heteroatom (or other readily substituted group) 7 so that it can be activated toward transmetalation on treatment with a fluoride source or a base. 8 "Safety-catch" silanols, which are stable to conditions
Silylcarbonylation of Vinylsilanes Catalyzed by Iridium(I) Siloxide Complexes
Organometallics, 2005
The iridium siloxide complexes [{Ir(µ-OSiMe 3 )(cod)} 2 ] (I) and [Ir(cod)(PCy 3 )(OSiMe 3 )] (II) were used as catalysts in the silylcarbonylation of CH 2 dCHSiMe 3 . While complex I effectively catalyzed the highly stereoselective formation of (E)-1-(dimethylphenylsiloxy)-1-(dimethylphenylsilyl)-3-(trimethylsilyl)-1-propene (1a, Me 3 SiCH 2 CHdC(OSiMe 2 Ph)SiMe 2 Ph; yield 82%), complex II led the reaction to stereoselective synthesis of (Z)-1-(dimethylphenylsiloxy)-3-(trimethylsilyl)-1-propene (2a, Me 3 SiCH 2 CHdCHOSiMe 2 Ph; yield 95%). The former product was used for synthesis of the acylsilane (Me 3 SiCH 2 CH 2 C(O)SiMe 2 Ph) (4a; yield 92%), a wellknown reagent in organic synthesis. Under a CO atmosphere the cyclooctadiene ligand in both complexes was replaced by CO, and the X-ray structure of [Ir(CO) 2 (PCy 3 )OSiMe 3 ] (IV) was resolved.
European Journal of Organic Chemistry, 2010
The design and development of highly efficient and selective methods for the synthesis of π-conjugated arylvinyl derivatives, based on sequential catalytic reactions of organometallic reagents, have been the subject of extensive study because of their versatile application in organic synthesis and materials science. The silylative coupling of olefins with vinyl-substituted silicon compounds represents one of the most efficient and selective methods for the synthesis of alkenylsilanes, which are particularly attractive scaffolds for further
The Journal of Organic Chemistry, 1980
fraction eft) of unconveIted 1 a t time t was determined from the IR spectra by using the ratio of the intensity of the absorption band at 5.7 pm, which is due to the carbonyl band for 1, to the intensity of the absorptiion band at 6.2 pm, which is an aromatic band found in all samples and, consequently, remains relatively constant. The decrease in ft as a function of t is first order as shown in , from which was deduced that the half-life of 1 under these conditions is about 90 h.
Organometallics, 2002
This paper reports the first successful synthesis of iridium-siloxide complex [{Ir(cod)(µ-OSiMe 3 )} 2 ] (I), whose structure has been determined by X-ray diffraction. Complex I has an A-frame bis-square planar geometry and is a selective catalyst of silylative heterocoupling of styrene with vinyltrisubstituted silanes CH 2 dCHSiR 3 (A) (where R 3 ) Me 3 , Me 2 Ph, (OEt) 3 ), Me 2 (OSiMe 3 ), Me(OSiMe 3 ) 2 ) and/or of hydrovinylation (co-dimerization) of styrene with vinylsilanes CH 2 dCHSi(OR′) 3 (B) (where R′ ) SiMe 3 , tert-Bu). Results of a stoichiometric study of I with substrates and labeling experiments (GC-MS and 1 H NMR analysis) with the deuterated styrene indicate the exchange of the vinylic proton and a non-metallacarbene mechanism of the two reactions proceeding via generation of active Ir-H intermediates by oxidative addition of dC-H to monomeric iridium-siloxide complexes. All the data allowed us to propose a reasonable mechanism of the silylative coupling, which does not involve migratory insertion of olefin into the Ir-Si bond as well as a mechanism of the hydrovinylation (co-dimerization) of styrene with vinyltris(trimethylsiloxy)silane.
Organic Letters, 2010
B(C 6 F 5 ) 3 promotes regio-and stereoselective cyclizations of unsaturated alkoxysilanes to generate oxasilinanes and oxasilepanes. The same products are available directly from alkenols via tandem silylation and hydrosilylation. Intramolecular hydrosilylation of alkenes is an important transformation in organic synthesis.1 Initially investigated for unsaturated silanes,2 the methodology is now often applied to unsaturated alkoxy-and aminosilanes,3 where stereospecific oxidative cleavage of the newly formed C-Si bond enables stereodefined synthesis of diols and aminoalcohols. 4 , 5 The majority of examples involve metal-catalyzed 5-endo or 5-exo ring closures, although six-membered cyclizations have been reported.1 , 3 , 6 We now report regio-and stereoselective formation of oxasilinanes and oxasilepanes via formation and cyclization of unsaturated alkoxysilanes in the presence of a nonmetal catalyst.
Journal of Molecular Catalysis, 1992
of vinyl-substituted silicon compounds containing methyl, aikoxyl, phenyl, trimethylsiloxyl and silatranyl groups at silicon with I-decene occurs effectively in the presence of benzene solutions of RuCI,(PPh,), activated by dioxygen. The nature of the substituent had only minor effects on the initial rate of substrate consumption and ethene evolution. The results obtained are discussed in view of two proposed mechanisms involving a ruthenium-carbene intermediate as well as insertion of alkene into the Ru-Si bond (and vinylsilane into the Ru-H bond) with elimination of silylalkene from p-alkylsilyl ligands (ethylene from j?-ethylsilyl ligands).