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Deuterium-labeling experiments were performed for the Fe(PMe3)4-catalyzed C–H/olefin coupling using a deuterium-labeled aromatic ketone with various alkenes. While the reactions with a variety of alkenes provided the linear alkylation products formed via 1,2-insertion of alkene into an Fe–H bond, the reversible 2,1-insertion proceeded during the reaction highly depends on the choice of the alkene. No H/D scrambling resulting from 2,1-insertion/β-elimination was detected for the reactions with a vinylsilane and N-vinylcarbazole, but the reactions­ with styrenes are considered to involve rapid 2,1-insertion/ β-elimination processes to cause significant levels of H/D scrambling.

A two‐step sequence for the enantio‐ and diastereoselective synthesis of exclusively alkyl‐substituted acyclic allylic systems with a stereocenter in the allylic position is reported. The asymmetric induction and the site selectivity are controlled in an enantio‐ and regioconvergent nickel‐catalyzed C(sp3)−C(sp3) cross‐coupling of regioisomeric mixtures of racemic α‐/γ‐silylated allylic halides and primary alkylzinc reagents. The silyl group steers the allylic displacement towards the formation of the vinylsilane regioisomer, and the resulting C(sp2)−Si bond serves as a linchpin for the installation of various C(sp3) substituents in a subsequent step., A nickel‐catalyzed cross‐coupling of regioisomeric mixtures of racemic silylated allylic halides and primary alkylzinc reagents enables the enantio‐ and regioconvergent synthesis of vinylsilanes with an allylic stereocenter. The silyl group controls the regiochemical outcome and is at the same time a placeholder for another alkyl substituent that can be installed in a subsequent cross‐coupling.

The branch-selective C–H alkenylation with alkenes using an iridium catalyst is reported. The Ir(III)-catalyzed reaction of aniline derivatives that contain a pyrimidine-directing group with vinyls...

We herein disclose the first Ni-catalyzed Hiyama coupling of aryl halides with vinylsilanes. This protocol uses cheap, nontoxic, and stable vinyltrimethoxysilane as the vinyl donor, proceeds under mild and ligand-free conditions, furnishing a diverse variety of styrene derivatives in high yields with excellent functional group compatibility.

The hydrosilylation of alkynes is a powerful process for producing vinylsilane compounds, which are synthetically versatile organosilicon reagents in organic chemistry. Herein, atomically dispersed Au anchored on g-C3N4 nanosheets is developed as a superior catalyst for the alkyne hydrosilylation reaction. The atomic Au species are in the +1 oxidative state coordinating with three nitrogen atoms observed via X-ray absorption fine structure (XAFS) characterization and analysis. Aromatic alkynes and aliphatic alkynes with various functional groups can effectively produce corresponding β-(E)-vinylsilane products with high conversion and selectivity. The atomically dispersed Au catalyst could be reused at least for five cycles without obvious decline in activity and selectivity. The unique structural and electronic characteristic of AuI–N3 sites are conducive to the successive activation of Si–H bonds, which boost the superior activity and selectivity of the single atom site Au in alkyne hydrosilylation.

International audience; Commercially available Ni(II) and Co(II) complexes – M(acac)2 (acac = acetylacetonate) and M(tmhd)2 (tmhd = 2,2,6,6-tetramethyl-3,5-heptanedionato) – exhibit catalytic activity for alkene/vinylsilane dehydrogenative silylation (DS) and hydrosilylation (HS) with tertiary silanes without the use of any external reducing agents. Using the model compounds divinyltetramethylsiloxane a.k.a dvtms and vinylpentamethyldisiloxane a.k.a vpmds, different selectivities (HS, DS, undesired non-C–Si bond-forming reactions…) are observed whether nickel or cobalt catalysts are employed, with Ni being DS-selective and Co yielding bothHS and DS products. All four complexes are efficient at thermally inducing silicone-oil crosslinking under a non-inert atmosphere, and promote metal-dependent selectivity that is slightly different from model reactions, which HR-MAS NMR spectroscopy unveils. Additional observations as well as NMR studies of [Ni(tmhd)2 + reagent] mixtures provide some insights into the possible activation pathways.

The cross-electrophile coupling has become a powerful tool for C-C bond formation, but its potential for forging the C-Si bond remains unexplored. Here we report a cross-electrophile Csp2 -Si coupling reaction of vinyl/aryl electrophiles with vinyl chlorosilanes. This new protocol offers an approach for facile and precise synthesis of organosilanes with high molecular diversity and complexity from readily available materials. The reaction proceeds under mild and non-basic conditions, demonstrating a high step economy, broad substrate scope, wide functionality tolerance, and easy scalability. The synthetic utility of the method is shown by its efficient accessing of silicon bioisosteres, the design of new BCB-monomers, and studies on the Hiyama cross-coupling of vinylsilane products.

Sila-molecules have recently attracted attention due to their promising applications in medical and industrial fields. Compared with all-carbon parent compounds, the different covalent radius and electronegativity of silicon from carbon generally endow the corresponding sila-analogs with unique biological activity and physicochemical properties. Vinylsilanes feature both silyl-hyperconjugation effect and versatile reactivities, developing vinylsilane-based Smiles rearrangement will therefore provide an efficient platform to assemble complex silacycles. Here we report a practical Ir(III)-catalyzed cycloaromatization of ortho-alkynylaryl vinylsilanes with arylsulfonyl azides for delivering naphthyl-fused benzosiloles under visible-light photoredox conditions. The combination of experiments and density functional theory (DFT) energy profiles reveals the reaction mechanism involving α-silyl radical Smiles rearrangement., Arene-fused siloles have attracted interest due to their promising applications in electronic and optoelectronic devices. Here, the authors report Ir(III)-catalyzed cycloaromatization of ortho-alkynylaryl vinylsilanes with arylsulfonyl azides via α-silyl radical Smiles rearrangement for accessing naphthyl-fused benzosiloles under visible-light photoredox conditions.

Here, we describe simple B(C6F5)3-catalyzed mono- and dihydrosilylation reactions of terminal alkynes by using a silane-tuned chemoselectivity strategy, affording vinylsilanes and unsymmetrical geminal bis(silanes). This strategy is applicable to the dihydrosilylation of both aliphatic and aryl terminal alkynes with different silane combinations. Gram-scale synthesis and conducting the reaction without the exclusion of air and moisture demonstrate the practicality of this methodology. The synthetic utility of the resulting products was further highlighted by the structural diversification of geminal bis(silanes) through transforming the secondary silane into other silyl groups. Comprehensive theoretical calculations combined with kinetical isotope labeling studies have shown that a prominent kinetic differentiation between the hydrosilylation of alkynes and vinylsilane is responsible for the chemoselective construction of unsymmetrical 1,1-bis(silanes)., A B(C6F5)3/silane-based system enables the chemoselective dihydrosilylation of terminal alkynes. Using a combination of different types of hydrosilanes, a series of unsymmetrical or symmetrical 1,1-bis(silanes) could be constructed.

A set of iridium(I) complexes of formula IrCl(κC,η2-IRCouR′)(cod) or IrCl(κC, η2-BzIRCouR′)(cod) (cod = 1,5-cyclooctadiene; Cou = coumarin; I = imidazolin-2-carbene; BzI = benzimidazolin-2-carbene) have beeen prepared from the corresponding azolium salt and [Ir(μ-OMe)(cod)]2 in THF at room temperature. The crystalline structures of 4b and 5b show a distorted trigonal bipyramidal configuration in the solid state with a coordinated coumarin moiety. In contrast, an equilibrium between this pentacoordinated structure and the related square planar isomer is observed in solution as a consequence of the hemilability of the pyrone ring. Characterization of both species by NMR was achieved at the low and high temperature limits, respectively. In addition, the thermodynamic parameters of the equilibrium, ΔHR and ΔSR, were obtained by VT 1H NMR spectroscopy and fall in the range 22–33 kJ mol−1 and 72–113 J mol−1 K−1, respectively. Carbonylation of IrCl(κC,η2-BzITolCou7,8-Me2)(cod) resulted in the formation of a bis-CO derivative showing no hemilabile behaviour. The newly synthesised complexes efficiently catalyze the hydrosilylation of alkynes at room temperature with a preference for the β-(Z) vinylsilane isomer.

The first example of palladium-catalyzed chelation-assisted C–H olefination of 2-amino biaryls using readily available vinylsilanes as unactivated olefinating reagents has been developed, affording valuable arylated vinylsilane compounds in moderate to excellent yields and with exclusive (E)-selectivities.

In this work, polyethylene/graphene oxide nanocomposites were synthesized and characterized. The graphene oxide (GO) was first functionalized with vinylsilane groups, and then it was grafted (g) with polyethylene chains by in situ polymerization, using a metallocene/MAO catalytic system. Through this method the GO particles were exfoliated and homogeneously dispersed across the nanocomposites, which consisted of high-density polyethylene (HDPE) and polyethylene-g-GO hybrid. The polyethylene-g-GO hybrid was Soxleht extracted and analyzed. It was found that the morphology and thermal properties (crystallization temperature and enthalpy) of nanocomposites are markedly affected by small increments of GO. For the polyethylene-g-GO hybrids the crystallization was suppressed by confinement effects and anchoring, both reducing the chain mobility. Finally, the thermally treated (200 °C for 10 min) polyethylene/GO nanocomposites, prepared via in situ polymerization, showed a low percolation threshold (around 0.1 wt%) and good electric conductivity (10−2 S cm−1).

We developed an enantioselective carbonyl-ene-type cyclization using 2-substituted vinylsilane as a nucleophilic ene moiety catalyzed by a chiral copper-BOX complex. This reaction is the first example of enantioselective carbonyl-ene cyclization using a 1,2-disubstituted olefin. This methodology gave chiral indenols with a tetrasubstituted carbon.

In the catalytic cross-coupling reaction of ketimines, derived from 1-acetonaphthone or acetophenone derivatives and benzylamine, with trialkoxyvinylsilanes RuH2(PPh3)4 or RuH2(CO)(PPh3)3 catalyst caused the selective alkenylation and alkylation on each aromatic ring of the ketimines separately (i.e. dual-mode coupling). Alkenylation occurred at the ortho-position(s) of the benzyl unit and alkylation occurred at the ortho-position(s) of 1-arylethylidene moiety of the substrates. By the stoichiometric reaction of N-1-(4-methylphenyl)ethylidene-4-methylbenzylamine with RuH2(CO)(PPh3)3 in the presence of three equivalents of vinylsilane, a novel ruthenium bismetallacylclic complex with two ruthenium-carbon bonds was isolated. This (C,N,C)-bismetallacycle complex was converted to the alkenylated complex by the reaction with two equiv. of vinylsilane. These observations indicate that the dual-mode coupling proceeds in a sequence of alkenylation followed by alkylation via intermediary bismetallacyclic complex formation.

Time-resolved investigation of deuterium-substituted silylene (SiD2) generated by laser flash photolysis of deuterium-substituted phenylsilane (PhSiD3) was carried out to obtain rate constants for its bimolecular reaction with ethylene (C2H4). The reaction was studied in the gas phase over the pressure range of 1–100 Torr (in SF6 bath gas) at 295 K. The rate constants for SiD2 + C2H4 were found to be independent of pressure and close in magnitude to the rate constants for the reaction of SiH2 + C2H4 at the high-pressure limit. They are consistent with a rapid isotopic scrambling mechanism similar to that of SiH2 + C2D4. While silirane, the main product produced from this reaction, was too labile to be detected, vinylsilane, another possible product, was ruled out by gas chromatography analysis. This reaction shows similarities to those of SiH2 + H2 and its isotopic counterparts.

The reactions of sulfonamidation of 1,1,3,3-tetramethyl-1,3-divinyldisiloxane, (allyloxy)trimethylsilane, trimethoxy(vinyl)silane and tris(2-methoxyethoxy)vinylsilane with trifluoromethanesulfonamide, arenesulfonamides and methanesulfonamide in the presence of (t-BuOCl + NaI) or N-bromosuccinimide proceed in a different manner depending on the substrate, reagent, and oxidant. The formation of the products of halosulfonamidation, heterocyclization, halogenation, solvent interception and desilylation is observed.

A novel three-dimensional coordination network 1 in a new 4,5,6-connected topology (4,5,6T115) built from linear CuII4Cl3(H2O)2 clusters and tetrahedral tetrakis(3-pyridyl)vinylsilane ligands is reported. Utilizing a similar tetrahedral ligand, tetrakis(3-pyridyl)ethylsilane, a different framework 2 having CuII2Cl(H2O)2 clusters is obtained in tcs topology. The activated sample of 1 shows an excellent and reversible uptake of I2 in solid as well as in solution phases owing to the presence of uncoordinated chloride ions and electron rich vinylic groups in it. The I2 uptake studies on the anion-exchanged samples, of bromide, iodide, and nitrate ions, show a progressive decrease in the adsorption capacity with the sample containing uncoordinated Cl– ion showing a maximum uptake of 48.5% and the one with the NO3– ions exhibiting the lowest uptake of 24.0%. These observations suggest that the halide counterions interact better with I2 in comparison with nitrate ions and the better I2 uptake in the presence of ...

The reactions of N,N-dichloroarenesulfonamides with chloromethyl(dimethyl)vinylsilane or of N,N-dichlorotrifluoromethanesulfonamide with chloropropyl(dimethyl)vinylsilanegive the NH- and NCl-containing products of chlorosulfonamidation of the double bonds. In contrast, N,N-(dichloro)trifluoromethanesulfonamide reacts with chloromethyl(dimethyl)vinylsilane to afford 4-chloro-3,3-dimethyl1-[(trifluoroethyl) sulfonyl]-1,3-azasilolidine via intramolecular heterocyclization.

A novel method of metal-free dehydrogenative silylation of enamides has been developed. The desired functionalized vinylsilane products were obtained in moderate to good yield and with high stereoselectivities. This protocol displays good tolerance of various functionalities. Furthermore, the high chemoselectivity of this reaction enables us to introduce different unsaturated C-C moieties to the products. The ease of further derivatization of the products to other useful compounds also demonstrates the highly synthetic utility of the current methodology.

The zwitterionic compound [Cp*RhCl{(MeIm)2CHCOO}] is an efficient catalyst for the hydrosilylation of terminal alkynes with excellent regio- and stereoselectivity toward the less thermodynamically stable β-(Z)-vinylsilane isomer under mild reaction conditions. A broad range of linear 1-alkynes, cycloalkyl acetylenes, and aromatic alkynes undergo the hydrosilylation with HSiMe2Ph to afford the corresponding β-(Z)-vinylsilanes in quantitative yields in short reaction times. The reaction of aliphatic alkynes with HSiEt3 is slower, resulting in a slight decrease of selectivity toward the β-(Z)-vinylsilane product, which is still greater than 90%. However, a significant selectivity decrease is observed in the hydrosilylation of aromatic alkynes because of the β-(Z) → β-(E) vinylsilane isomerization. Moreover, the hydrosilylation of bulky alkynes, such as t-Bu–C≡CH or Et3SiC≡CH, is unselective. Experimental evidence suggests that the carboxylate function plays a key role in the reaction mechanism, which has been validated by means of density functional theory calculations, as well as by mass spectrometry and labeling studies. On the basis of previous results, we propose an ionic outer-sphere mechanism pathway in which the carboxylate fragment acts as a silyl carrier. Namely, the hydrosilylation mechanism entails the heterolytic activation of the hydrosilane assisted by the carboxylate function to give the hydrido intermediate [Cp*RhH{(MeIm)2CHCOO–SiR3}]+. The transference of the silylium moiety from the carboxylate to the alkyne results in the formation of a flat β-silyl carbocation intermediate that undergoes a hydride transfer from the Rh(III) center to generate the vinylsilane product. The outstanding β-(Z) selectivity results from the minimization of the steric interaction between the silyl moiety and the ligand system in the hydride transfer transition state., The authors express their appreciation for the financial support from the Spanish Ministry of Economy and Competitiveness MINECO/FEDER under the project CTQ2016-75884-P and the Regional Governments of Aragón/FEDER 2014–2020 “Building Europe from Aragón” (group E42_17R). In addition, the resources from the supercomputer “Memento,” technical expertise, and assistance provided by BIFIZCAM (Universidad de Zaragoza) are acknowledged.

Strong Bronsted-base-catalyzed addition reactions of alkylazaarenes with vinylsilanes are reported. The reactions of alkylpyridines and their analogues with vinylsilanes proceed in moderate to high yields in the presence of catalytic amounts of LiTMP, LiCl, and MS 4A. This is a general method that can be applied to catalytic addition reactions of alkylazaarenes with vinylsilanes.

A convenient strategy for synthesis of the various derivatives of 1,4-dihydropyridine (1,4-DHP), as one of the most important pharmaceutical compounds, is presented in this study. For this purpose, firstly, magnetic iron oxide nanoparticles (Fe3O4 NPs) were fabricated and suitably coated by silica network (SiO2) and trimethoxy vinylsilane (TMVS). Then, their surfaces were well functionalized with pyrimidine-2,4-diamine (PDA) as the main active sites for catalyzing the synthesis reactions. In this regard, the performance of three different methods including reflux, microwave (MW) and ultrasound wave (USW) irradiations have been comparatively monitored via studying various analyses on the fabricated nanocatalyst (Fe3O4/SiO2-PDA). Concisely, high efficiency of the USW irradiation (in an ultrasound cleaning bath with a frequency of 50 kHz and power of 250 W/L) has been well proven through the investigation of the main factors such as excellent surface-functionalization, core/shell structure conservation, particle uniformity, close size distribution of the particles, and great inhibition of the particle aggregation. Then, the effectiveness of the USW irradiation as a promising co-catalyst agent has been clearly demonstrated in the 1,4-DHP synthesis reactions. It has been concluded that the USW could provide more appropriate conditions for activation of the catalytic sites of Fe3O4/SiO2-PDA NPs. However, high reaction yields (89%) have been obtained in the short reaction times (10 min) due to the substantial synergistic effect between the presented nanocatalyst and USW.

The formation of a family of silicon- and siloxane-bridged multiferrocenyl derivatives carrying different functional groups attached to silicon, including Fc2(CH3)3C(CH2)2SiCH[double bond, length as m-dash]CH2 (5), Fc2(CH2[double bond, length as m-dash]CH-O)SiCH[double bond, length as m-dash]CH2 (6), Fc2(OH)SiCH[double bond, length as m-dash]CH2 (7), Fc2(CH2[double bond, length as m-dash]CH-O)Si-O-Si(O-CH[double bond, length as m-dash]CH2)Fc2 (8) and Fc2(CH2[double bond, length as m-dash]CH-O)Si-O-SiFc3 (9) is described. Silyl vinyl ether molecules 6, 8 and 9 and the heteroleptic vinylsilane 5 resulted from the competing metathesis reaction of lithioferrocene (FcLi), CH2[double bond, length as m-dash]CH-OLi or (CH3)3C(CH2)2Li with the corresponding multifunctional chlorosilane, Cl3SiCH[double bond, length as m-dash]CH2 or Cl3Si-O-SiCl3. The last two organolithium species have been likely formed in situ by fragmentation of the tetrahydrofuran solvent. Diferrocenylvinyloxyvinylsilane 6 is noteworthy since it represents a rare example of a redox-active silyl mononomer in which two different C[double bond, length as m-dash]C polymerisable groups are directly connected to silicon. The molecular structures of the silicon-containing multiferrocenyl species 5, 6, 8 and 9 have been investigated by single-crystal X-ray diffraction studies, demonstrating the capture and storage processes of two ring fragments resulting from the cleavage of cyclic THF in redox-active and stable crystalline organometallic compounds. From electrochemical studies we found that by changing the anion of the supporting electrolyte from [PF6]- to [B(C6F5)4]-, the redox behaviour of tetrametallic disiloxane 8 can be switched from a poorly resolved multistep redox process to four consecutive well-separated one-electron oxidations, corresponding to the sequential oxidation of the four ferrocenyl moieties.

We report here that a cobalt catalyst generated from a cobalt(II) salt and a ligand using magnesium metal is capable of promoting hydroarylation reactions through chelation-assisted C−H activation. With the appropriate choice of the ligand and other reaction conditions, ketimine- or aldimine-directed branched selective hydroarylations of styrenes and ketimine-directed hydroarylations of vinylsilane have been achieved. The reported catalytic systems may serve as more convenient alternatives to previously developed catalytic systems employing Grignard reagents as reducing agents. MOE (Min. of Education, S’pore) Accepted version

A general route to several styryl-lactone frameworks is presented. Starting from a known enol ether, stereoselective epoxidation and methanolysis yields a series of three distinct hydroxyacetals, each further functionalized by etherification with an allylic vinylsilane fragment. A highly efficient Lewis acid-promoted intramolecular annulation at the tethered oxocarbenium allows direct entry to cis-fused bicyclic ether cores. Further manipulation delivers a variety of additional styryl-lactone motifs and analogs; for example, simple allylic oxidation yields 3-deoxyisoaltholactone, in just five steps overall.

Vinylsilanes are versatile and efficient nucleophiles in cross-coupling reactions. Herein is described the use of tetrabutylammonium bifluoride as a mild, cheap and scalable activating agent in several copper-catalyzed vinylsilane cross-couplings.

The hydrophilic surfaces of nanosilica particles were modified to achieve a hydrophobic characteristic using a vinylsilane coupling agent. The effects of the modified nanosilica content on the electrical and mechanical properties of a silicone rubber nanocomposite were studied for application toward heavy electrical equipment. The modification of the nanosilica particles was confirmed using Fourier-transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). A silicone rubber nanocomposite was prepared by mixing liquid silicone rubber (LSR) with vinylsilane-modified nanosilica particles at a weight ratio of 100 to 0–30 g. To observe the even dispersion of nanosilica particles in the LSR matrix, transmission electron microscopy (TEM) was used and it was found that the surface-modified nanosilicas were well dispersed in a 52–78 nm cluster formation. The electrical (alternating current (AC) breakdown strength and dielectric properties) and mechanical (tensile strength and elongation) properties were measured, and the AC insulation breakdown strength and tensile strength increased with an increase in the amount of modified-nanosilica.

The functionalization of polysilanes is an important subject in materials science because functionalized polysilanes are expected to exhibit potentially innovative properties. This research aims at the addition of a water-shedding property to polysilanes by introducing perfluoroalkyl groups into their skeleton. The photoinduced iodoperfluoroalkylation of various vinylsilanes takes place successfully upon irradiation with a xenon lamp: vinylmonosilanes undergo iodoperfluoroalkylation with perfluoroalkyl iodides (RfI) regioselectively, and the corresponding perfluoroalkylated silanes are obtained in moderate to high yields. Detailed optimization of the photoinduced iodoperfluoroalkylation has been investigated to apply this method to the functionalization of polysilanes. Polysilanes having vinyl groups can be synthesized by the reductive coupling of dichlorovinylsilanes with samarium diiodide (SmI2) and samarium metal (Sm) upon irradiation with visible light. The synthesized vinylpolysilanes and RfI (about 1.0 mM CHCl3 solution) are coated on a glass plate sequentially, and then the following photoirradiation with light of a wavelength over 300 nm successfully adds an excellent water-shedding property to the glass plate.

The creation of three consecutive chiral carbon centers in one step is achieved using Cu-catalyzed asymmetric silylative cyclization of cyclohexadienone-tethered allenes. Through regioselective β-silylation of the allene and subsequent enantioselective 1,4-addition to cyclohexadienone, this tandem reaction could afford cis-hydrobenzofuran, cis-hydroindole, and cis-hydroindene frameworks with excellent yields (80-98%) and enantioselectivities (94-98% ee) bearing vinylsilane and enone substructures. Meanwhile, this mild transformation is generally compatible with a wide range of functional groups, which allows further conversion of the bicyclic products to bridged and tricyclic ring structures.

The hydrosilylation of alkenes catalyzed by Fe(CO) 5 is an intricate process involving formation of alkylsilane, vinylsilane, and alkane. Herein, we represent a computational study of this reaction to determine the underlying reaction mechanism using density functional theory (DFT) techniques. On the basis of an extensive exploration of the potential energy surfaces, the modified Chalk–Harrod mechanism was found to be competitive with the Chalk–Harrod mechanism in the stoichiometric reaction of ethylene and trimethylsilane. The source of product selectivity was predicted to be determined by the relative stability of transition state TS(4b–5b) , which is for the ethylene-insertion into Fe Si bond from (H)(Me 3 Si)Fe(CO) 3 (C 2 H 4 ) to (H)(C 2 H 4 SiMe)Fe(CO) 3 , and TS(5a–7a 1 ) for the conversion of ethylene hydrometallation product (Me 3 Si)Fe(CO) 3 (η 2 -H)(C 2 H 4 ) to (C 2 H 5 )(Me 3 Si)Fe(CO) 4 . The relative free energy difference of 3.27 kcal/mol between these two transition states gives a percentage ratio of 79:21 for C 2 H 5 SiMe 3 to C 2 H 4 SiMe 3 , which is qualitatively in agreement with the experimental observations. The largely excessive ethylene favors not only the formation of Fe(CO) 3 (C 2 H 4 )(H)(SiMe 3 ) 4b but also the release of vinylsilane from Fe(CO) 3 (H 2 )(C 2 H 3 SiMe 3 ) or Fe(CO) 4 (C 2 H 3 SiMe 3 ) via the addition of another ethylene molecular to the metal center. Alternatively, in the presence of excessive R 3 SiH, species Fe(CO) 4 (H)(SiR 3 ) will be dominate over Fe(CO) 4 (C 2 H 4 ). In the catalytic process, Fe(CO) 4 (H)(SiR 3 ) plays the main role of active species. The experimental findings were rationalized in terms of two reaction pathways, the accessibility of which depended on the ratio of silane/alkene.

The application of 1,3-divinyl-1,3-dimethyl-1,3-diferrocenyldisiloxane [(CH2═CH)FcMeSi]2O (1) as an efficient electroactive vinylsilane precursor for thiol–ene radical reactions is described. In order to determine if steric or electronic limitations due to the redox-active metallocene moiety might affect the bis(hydrothiolation) of the bifunctional vinylsilane, a model reaction was initially performed between 1 and 2-mercaptoethanol, resulting in the formation of the newly sulfur-containing carbosiloxane 2 in excellent yield. The bis(thiol–ene) reaction of 1 was successfully extended to 2,2′-(ethylenedioxy)diethanethiol, affording a series of novel precisely defined, redox-active oxathiacrown macrocycles (3 and 4n) and sulfur-bearing linear oligo-carbosiloxanes (5n and 6n) with a backbone in which the −S(CH2)2–O(CH2)2O–(CH2)2S– chain and the −Si–O–Si– bond, bearing pendant ferrocenes, are alternately linked by ethylene bridges. These reactions have been initiated either thermally (in toluene solution with...

Conversion of α-amino aldehydes into protected amino-hydroxy-methyl stereotriads carrying an E-trisubstituted vinyl iodide unit was effected by means of a three-step protocol: a Marshall reaction of the α-amino aldehyde with a chiral propargylic mesylate, a silylcupration of the corresponding homopropargylic alcohol and an iododesilylation reaction of the resulting vinylsilane. This sequence delivered the expected compounds as their oxazolidinone derivatives, providing a convenient diastereoselective access to useful building blocks for polypropionate synthesis and polyketide derivatives.

The intramolecular trans-silylruthenation of internal alkynes and subsequent insertion of vinyl boronates is described. This approach provides complete regiocontrol through a stereoselective trans-5-exo-dig cyclization which affords a tetrasubstituted olefin as a vinylsilane and a highly functionalized Z,E diene motif.

Oxide-supported rhodium catalysts with excellent activity in silylative coupling reactions have been developed. Reductive pretreatment of the catalysts in the presence of 0.5 equiv triphenylphosphine under a hydrogen atmosphere enhanced and stabilized the catalytic activity. Of the catalysts examined, ceria-supported rhodium had the highest activity in the homo-coupling of vinylsilanes to bis(silyl)ethenes at 170 °C. A zirconia-supported catalyst selectively gave E-1-aryl-2-silylethenes by cross-coupling of vinylsilanes with styrenes at 130 °C, and a high turnover frequency of >8200 h−1 was achieved at 170 °C. Spectroscopic studies revealed that well-dispersed surface rhodium(I) species predominantly formed on ceria or zirconia were transformed into rhodium hydride species, which are believed to be responsible for the high activity. These catalysts were recyclable without loss of activity, and leaching of rhodium species from the catalysts was not observed.

A new method for introducing robustly bound organic functional groups on silica surfaces is developed. Compared to conventional monomer immobilization procedures, the new vinylsilane-impregnated polymer based protocol can be employed for the preparation of various organic group functionalized silicas that are stable under both acidic and basic conditions. Organic functional groups can be readily introduced by one-step Rh(I)-catalyzed hydroacylation reaction or appended by Suzuki coupling reactions.

The ruthenium hydride complex (PCy3)2(CO)RuHCl was found to be a highly effective catalyst for the regio- and stereoselective hydrosilylation of alkynes to form vinylsilane products. (Z)-Vinylsilane products were selectively formed for sterically nondemanding terminal alkynes, while (E)-vinylsilane products resulted from sterically demanding terminal alkynes. Kinetic data were obtained from the hydrosilylation of phenylacetylene. The phosphine inhibition study showed an uncompetitive Michaelis–Menten type of inhibition kinetics. The empirical rate law rate = kobs[1]1[alkyne]0[silane]0 was established from the reaction rate as a function of both [alkyne] and [silane]. DFT calculations were performed and found that Z/E isomerization is facile via a metallacyclopropene transition state and that the isomerization occurs prior to the silane substrate binding. A detailed mechanistic scheme on the hydrosilylation reaction has been delineated on the basis of both experimental and computational data.

Mg-promoted reductive silylation of 4-phenyl-3-butyn-2-one in N,N-dimethylformamide (DMF) in the presence of chlorotrimethylsilane brought about double silylation at the β-carbon and oxygen atoms of the carbonyl group to give a multifunctionalized allene with a vinylsilane moiety and a silyl enol ether moiety. A variety of allenes can be synthesized through this simple methodology. Acid-catalyzed hydrolysis of an allene derived from the trimethylsilylation of 4-phenyl-3-butyn-2-one resulted in the formation of the corresponding benzalacetone with a trimethylsilyl group at the β-position of the carbonyl group in high yield.

The mechanisms and origins for the Pd- and Ni-catalyzed regioselective hydrosilylation of allene have been investigated by means of density functional theory (DFT) calculations. The free-energy profiles of Pd- and Ni-catalyzed reactions with small and bulky N-heterocyclic carbene (NHC) ligands are calculated to determine the mechanism for regioselectivities. The calculation results show that different metals (Ni vs Pd) lead to regiochemical reversals for the hydrosilylation of allene. The allylsilane is the major product via palladium catalysis with small NHC ligand, while the vinylsilane is the major product via nickel catalysis with bulky NHC ligand. Both electronic and steric factors play a key role in the regioselectivities for the hydrosilylation of allene via Pd and Ni catalysts. The calculation results are in good agreement with observed regioselectivities and could provide insights into the design of new catalysts for the regioselectivity of hydrosilylation reactions.

Controlling the chemical nature and functionality of a Pickering stabilizer in surfactant-free emulsion polymerization plays a salient role in the nucleation and growth of latex particles. Silane-functionalization of montmorillonite (Mt) platelets is expected to tune the partition behavior of the clay platelets toward a monomer phase and enhance their stabilizing ability in oil-in-water (o/w) system. Such fabrication should result in prompted heterogeneous coagulative nucleation of latex particles, and therefore, drive a fabrication of clay-hydrophobic polymer latex nanocomposites. In this paper, Pickering emulsion polymerizations of styrene and n-butyl acrylate, stabilized by Mt. platelets onto which various silane agents were chemically grafted, were formulated. Along with characterizations of silane-functionalization on Mt. platelets, a kinetic study on the clay-polymer latexes was performed via a dynamic light scattering method and morphological observations. Polystyrene latex particles stabilized by the silane-functionalized Mt. platelets showed faster heterocoagulative nucleation even at the early stage of particle formation, owing to their attractive interaction with the monomer. The secondary participation of vinyl moieties on the Mt. platelets in radical reactions was followed, and it reinforced the adsorption behavior via covalent linkages. This is the first report that presented kinetic evidence of an attractive interaction between hydrophobic monomers and silane-functionalized Mt. platelets which led to the formation of a clay-latex clustered structure.

Kinetics of the reactions of benzhydrylium ions (Aryl2CH+) with the vinylsilanes H2CC(CH3)(SiR3), H2CC(Ph)(SiR3), and (E)-PhCHCHSiMe3 have been measured photometrically in dichloromethane solution at 20 °C. All reactions follow second-order kinetics, and the second-order rate constants correlate linearly with the electrophilicity parameters E of the benzhydrylium ions, thus allowing us to include vinylsilanes in the benzhydrylium-based nucleophilicity scale. The vinylsilane H2CC(CH3)(SiMe3), which is attacked by electrophiles at the CH2 group, reacts one order of magnitude faster than propene, indicating that α-silyl-stabilization of the intermediate carbenium ion is significantly weaker than α-methyl stabilization because H2CC(CH3)2 is 103 times more reactive than propene. trans-β-(Trimethylsilyl)styrene, which is attacked by electrophiles at the silylated position, is even somewhat less reactive than styrene, showing that the hyperconjugative stabilization of the developing carbocation by the β-silyl effect is not yet effective in the transition state. As a result, replacement of vinylic hydrogen atoms by SiMe3 groups affect the nucleophilic reactivities of the corresponding CC bonds only slightly, and vinylsilanes are significantly less nucleophilic than structurally related allylsilanes. Die Kinetik der Reaktionen von Benzhydrylium-Ionen (Aryl2CH+) mit den Vinylsilanen H2CC(CH3)(SiR3), H2CC(Ph)(SiR3) und (E)-PhCHCHSiMe3 wurde in Dichlormethan bei 20 °C photometrisch bestimmt. Alle Reaktionen verlaufen nach einer Kinetik 2. Ordnung, und die Geschwindigkeitskonstanten 2. Ordnung korrelieren linear mit der Elektrophilie E der Benzhydrylium-Ionen, wodurch es moglich wird, Vinylsilane in die auf Reaktivitaten gegenuber Benzhydrylium-Ionen aufgebaute Nucleophilieskala aufzunehmen. Das Vinylsilan H2CC(CH3)(SiMe3), das von Elektrophilen an der CH2-Gruppe angegriffen wird, reagiert um eine Grosenordnung schneller als Propen, was darauf hinweist, dass die Stabilisierung des intermediaren Carbokations durch den α-Silyl-Effekt wesentlich schwacher ist als die Stabilisierung durch den α-Methyl-Effekt, da H2CC(CH3)2 103 mal reaktiver ist als Propen. trans-β-(Trimethylsilyl)styrol, das von Elektrophilen an der silylierten Position angegriffen wird, ist sogar etwas weniger reaktiv als Styrol, was zeigt, dass die hyperkonjugative Stabilisierung des entstehenden carbokationischen Zentrums im Ubergangszustand noch nicht wirksam ist. Somit beeinflusst der Austausch eines vinylischen Wasserstoffs durch eine SiMe3-Gruppe die nucleophile Reaktivitat der betrachteten CC Doppelbindung nur marginal, und Vinylsilane sind betrachtlich weniger nucleophil als strukturell verwandte Allylsilane.

Soft reaction conditions, particularly important in total synthesis, have dragged many researchers into the field of silylated organic compounds. Hereby, we describe a new copper-catalyzed vinylsilane transformation. Various vinylsilanes were allylated by using a copper(I) salt, and this led to the formation of polysubstituted 1,4-dienes bearing sensitive moieties such as halogens, ketones, and aldehydes. Hereby is described a new copper-catalyzed vinylsilane transformation. Various vinylsilanes were allylated by using copper(I) salts, and this led to the formation of polysubstituted 1,4-dienes bearing sensitive moieties such as halogens, ketones, and aldehydes. TBAT = tetrabutylammonium difluorotriphenylsilicate. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The highly regio- and diastereoselective rhodium-catalyzed [(3+2)+2] carbocyclization reaction of trialkoxysilyl-substituted alkenylidenecyclopropanes (ACPs) with monosubstituted alkynes is reported. This work represents the first example of a metal-catalyzed higher-order carbocyclization with a vinylsilane, which facilitates the regioselective insertion of the alkyne and the selective introduction of a secondary alcohol. For example, stereospecific Tamao oxidation of the allylsilane resulting from the stereoselective cycloaddition provides the corresponding C6 hydroxyl group that is present in an array of related sesquiterpene natural products.

A new ruthenium complex catalyzed procedure for the efficient O -silylation of an SiO–H group on the silica surface of glass beads with controlled pores (CPG) using 1-trimethylsiloxy-3-dimethylvinylsilylpropane leading to Si–O–Si bond formation with the evolution of ethylene is described. The formed linker contains alkyl hydroxyl groups which can be reacted with a nucleoside phosphoramidite unit. The CPG support containing alkyl hydroxyl groups is successfully applied in automatic chemical synthesis of DNA fragments.

Several methods for the preparation of (Z) trimethoxystyrene derivatives 1 were investigated. After finding that the Wittig reaction led to unsatisfactory results, three different strategies were considered: a Suzuki coupling with a stereodefined monobromoalkene, a combination of hydrosilylation/vinylsilane hydrolysis and a palladium-catalyzed semi-hydrogenation step, using DMF/KOH as the hydrogen source. Our studies led us to prepare a series of diarylacetylene derivatives via a Sonogashira coupling reaction, and also to find out a copper-free basic cyclization leading to benzo[b]thiophenes. The final choice for the synthesis method of 1 strongly depends on the target compound but the semi-hydrogenation, which avoids the use of a toxic tin reducing agent, should be generally preferred.

A pyridinebis(oxazoline) cobalt complex is a very efficient precatalyst for the hydrosilylation of terminal alkynes with Ph2 SiH2 , providing α-vinylsilanes with high (Markovnikov) regioselectivity and broad functional-group tolerance. The vinylsilane products can be further converted into geminal borosilanes through Markovnikov hydroboration with pinacolborane and a bis(imino)pyridine cobalt catalyst.