Vinyl silanes, dimerization

Cyclic seven-membered vinyl silanes 161 were obtained by regio- and stereoselective hydrosilylation of internal alkynes catalyzed by the ruthenium complex [Cp Ru(MeCN)3]PF6, as shown in Equation (33) <2005JA10028>. Hydrosilylation of 2,2-divinyladamantane with bis(hydrosilane) species 162 in the presence of Zeise s dimer [Pt2Cl4(CH2CH2)2] gave the disilacyclic 163 in high yields (Equation 34) <19980M4267>. 

Vinyl silanes too can be dimerized using Ziegler-type catalyst systems. For instance, trimethylvinylsilane yielded the linear dimer with the catalyst Ni(acac)2/Et3Al2CVPPh3 [62] and vinylsilanes containing methoxy groups reacted with a catalyst composed of tetrabutoxytitanium, PPh3 and AlEt3 in a 1 1 6 ratio [63] (Equation 45). 

This synthesis featured a four-component coupling involving an oxidative dimerization process. Treatment of homochiral acyl silane 56 with vinyl lithium at low temperature, followed by the addition of half an equivalent of iodine to the reaction mixture, furnished tetraene 58 in high yield and with a very high level of stereoselectivity. The TBS ether was then converted to its triflate equivalent 59 in a... 

Summary The synthesis of the first silicon complexes with the tridentate diketoamine HN[CH2C(rBu)=0]2 (1) is described. The reaction of YSiXs (X = Cl, Br Y = H, Cl, Br, Ph, Vinyl) with 5-aza-2,2,8,8-tetramethylnonane-3,7-dione (1) in the presence of NEtj as an auxiliary base furnished the unusual dinuclear silicon complexes (6-11) having pentacoordinate silicon centers. Theoretical calculations (B3LYP/6-31G ) carried out for the monomeric chloro-substituted silane 7A are consistent with a folded structure and a relatively short and highly polarized Si-N bond (1.742 A Charge Si 0.96 N -0.53). The calculated value for the dimerization energy of 7A is -29 kcal/mol, reflecting the presence of a partial Si-N it-bond. Thus, the novel dimeric silicon compound 7 is the result of a head-to-tail dimerization of formally two Si=N bonds in 7A. 

Functionally substituted benzylic, allylic, and vinylic compounds containing alkoxides, esters, ethers, nitriles, or amides can be reacted with halosilanes under Barbier conditions using HMPT to yield C- and O-silylated products, 1,2- or 1,4-addition products, as well as reductive dimers. Radical and anionic intermediates are postulated, based on SET reactions from the metal, and multiple silated species can be obtained. The use of the TMSCl-Mg-HMPT system has been extensively investigated by Galas group [85] at the University of Bordeaux, and their work has greatly advanced the science of the Barbier reaction with silanes. 

TMS-alkynes are oxidized at the terminal carbon to carboxylic acids by hydroboration/oxidation (dicyclohexylborane/NaOH, H2O2). This does not work with TIPS-alkynes. Instead, TIPS-alkynes are cleanly monohydroborated at the internal carbon by 9-borabicyclo[3.3.1]nonane dimer to give (Z)- -borylvinyl-silanes. These can be oxidized in high yields to a-silyl ketones, or cross coupled with a bromide R Br (R = aryl, benzyl, dimethyl-vinyl) in the presence of NaOH and tetrakis(triphenylphos-phine)palladium(0) to give /3,/3-disubstituted vinylsilanes (Suzuki reaction eq 14). The same nucleophilic substituted vinylsilane can be added to an aromatic aldehyde to provide access to ( )-3-silyl allyl alcohols. ... 

Other recent applications of ToF-SIMS without XPS include the examination of PS [6, 17-19], polyethylene (PE) [20], carbon fibre reinforced epoxy resins [21], polyalkyl methacrylates [22], alkylketene dimers [23], perfluorinated polymers [24], perflnorinated ethers [25], polyethylene glycol (PEG) oligomers [15, 25-29], rubber [30], ethylene-tetrafluoroethylene copolymer [30], Nylon-6 [31], PC [32,33], PDMS [34], polypyrrole coated PS [35], poly-p-phenylene vinylene [36], butyl rubber [37], poly(4-vinyl phenol)/poly(4-vinyl pyridine blends) [38], polypyrrole-silica gel composites [39], y-glycidoxypropyl trimethoxy silane [40], triblock copolymer poly(ethylene glycol)- 3 poly(phenylene ethylene)- 3 poly(ethylene glycol) [41], ethylene-terephthalate-hydroxybenzoate copolymer [42], PS-polyvinyl methyl ether, polycarbonate - PS blends [43] and PDMS-urethane [44],... 

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