Synthesis of new polysilane-crown ether

This paper presents the synthesis of new polysilane with pendant crown ether groups. The polymer was obtained through the addition reaction of 4^′-allylbenzo-15-crown-5 to poly[methyl(H)-co-methylphenylsilane] copolymer in anhydrous toluene solution using hexachloroplatinic acid as a catalyst. The allyl functionalization of the crown ether was achieved by the coupling of the crown ether bromide with allyl magnesium chloride. The availability of the crown ether sites in complexation reactions with Cu(II) cations was tested.The chemical structures of all products and intermediates were studied using spectral methods (IR, ¹H-NMR, ¹³C-NMR, UV), gel permeation chromatography (GPC) and thermogravimetric analysis (TGA).     

苯烷基、对氯甲基苯烷基硅化合物的合成及其聚合物的热稳定性研究

通过相应烯烃的硅氢化反应,合成了-(CH_2)_n-SiX_3(n=2,3,4;X=Cl.OCH_3)及ClCH_2-(CH_2)_NSiX_3(n=2.3;X=Cl.OCH_3)等两类新型有机硅化合物.比较了它们水解缩聚产物的热稳定性.结果表明,所合成的两类硅单体均具预定的化学结构.在H_2PtCl_6-P(C_6H_5)_3的催化下,硅氢化反应系按反-马尔可夫尼科夫规则进行.另外,这两类有机硅单体的水解缩聚产物的热稳定性与芳基的位置(β、γ或δ位)有关而以在β位的为最高.     

THE HYDROSILYLATION REACTION OF LADDERLIKE POLYVINYLSILSESQUIOXANE WITH 1, 1, 3, 3-TETRAMETHYLDISILOXANE

The hydrosilylation reaction of ladderlike polyvinylsilsesquioxane (Vi-T)with 1, 1, 3, 3-tetramethyldisiloxane (H- MM ) catalyzed by dicyclopentadienyl-dichloroplat-inium (Cp_2PtCl_2) was carried out well in tetrahydrofuran (THF) to produce a soluble whitesolid. This product was characterized by IR, ~1H-NMR, ~(13)C-NMR, ~(29)Si-NMR, DSC, X-raydiffraction method, gel permeation chromatography (GPC), vapour pressure osmometry(VPO), atomic force microscopy (AFM) and molecular simulation. These results provethat the product contains nanoscale tubular structure.     

Hydrosilylation of alkynes catalyzed by ruthenium carbene complexes

Hydrosilylation of terminal alkynes with a variety of silanes catalyzed by Cl₂(PCy₃)₂RuCHPh (1) affords mainly the Z-isomer via trans addition in excellent yields. The presence of a hydroxyl group in close proximity to the triple bond was observed to exert a strong directing effect, resulting in the highly selective formation of the α-isomer. Intramolecular hydrosilylation of a homopropargylic silyl ether was demonstrated to give the cis addition product.     

Novel Immobilized Hydrosilylation Catalysts Based on Rhodium 1,3-Bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidenes

Summary. The reactivity of a well defined Rh (I) complex, i.e. Rh(CF₃COO)(NHC)(COD) (1, NHC=1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene, COD=⁴-cycloocta-1,5-diene) in the hydrosilylation of 1-alkenes, alkynes, and ,-unsaturated carbonyl compounds, respectively, is described. With this complex, excellent reactivity was observed and turn-over numbers (TONs) up to 1000 were reached. A supported version of 1 was realized by reaction of RhCl(NHC)(COD) with PS-DVB–CH₂–O–CO–CF₂–CF₂–CF₂–COOAg (PS-DVB=poly(styrene-co-divinylbenzene) to yield PS-DVB–CH₂–O–CO–CF₂–CF₂–CF₂–COORh(NHC)(COD). This supported version of 1 exhibited at least comparable, in some cases increased reactivity compared to 1 and allowed the rapid removal of the catalyst from the reaction mixture. Due to reduced catalyst bleeding, the synthesis of target compounds with a Rh-content of less than 130ppm was accomplished.This revised version was published online in February 2005. In the previous version the issue was not marked as a special issue, and the issue title and the editor was missing     

Bis-paracyclophane N-heterocyclic carbene-ruthenium catalyzed asymmetric ketone hydrosilylation

New chiral bis-paracyclophane N-heterocyclic carbene (NHC) ligands 1-3 have been explored for ruthenium catalyzed asymmetric hydrosilylation of ketones using diphenylsilane to give enantioenriched alcohols. These ligands provide for efficient asymmetric reduction in the presence of silver(I) triflate (1 mol %) at room temperature with high reactivity and selectivity. Acetophenone 4 was reduced with 1 mol % catalyst in 96% isolated yield, 97% ee. Following removal of the silyl ether, various alcohols 5 were obtained from aromatic ketones in high yield and selectivity.     

Hydrosilylation and double silylation of carbonyl compounds with 1,1′-bis(dimethylsilyl)ferrocene using nickel- and platinum-catalysts

A series of ferrocene-based organosilicon compounds have been prepared via hydrosilylation or double silylation of carbonyl compounds with 1,1′-bis(dimethylsilyl)ferrocene using (C₂H₄)Pt(PPh₃)₂ or Ni(PEt₃)₄ catalysts. In general, while the platinum catalyst (C₂H₄)Pt(PPh₃)₂ preferentially produced cyclic double-silylated products, the Ni(PEt₃)₄ catalyst led to the hydrosilylated ferrocene products from aldehydes or ketones.     

Carbosiloxandendrimere mit terminalen SiH-Bindungen

An efficient method for the preparation of carbosiloxane dendrimers with end-grafted SiH-bonds is given by using the alcohols HOCH(Me)(CH₂)₄SiMe_3 − nH_n (4a: n = 1, 4b: n = 2, 4c: n = 3), which themselves are accessible by the hydrosilylation of MeCOCH₂CH₂CHCH₂ (1) with the chlorosilanes HSiMe_3 − nCl_n (2a: n = 1, 2b: n = 2, 2c: n = 3) and hydrogenation of the latter species with Li[AlH₄]. Alcohols 4a-4c can be used as starting materials for the preparation of carbosiloxane dendrimers of the 1^st-3^rd generation. For the synthesis of the 1^st generation dendrimers, Me_4 − mSiCl_m (5a: m = 1, 5b: m = 2, 5c: m = 3, 5d: m = 4) is reacted with 4a-4c in presence of NEt₃ as base. The dendritic molecules Me_4 − mSi[OCH(Me)(CH₂)₄SiMe_3 − nH_n]_m (n = 1: 6a, m = 1; 6b, m = 2; 6c, m = 3; 6d, m = 4. n = 2: 7a, m = 1; 7b,m = 2; 7c, m = 3; 7d, m = 4. n = 3: 8a, m = 3; 8b, m = 4) are thereby obtained in excellent yield. Carbosiloxane dendrimers of the 2^nd and 3^rd generation with a MeSiO₃- or SiO₄-core can be isolated from the reaction of MeSi(OCH₂CH₂CH₂SiMe₂Cl)₃ (9), MeSi(OCH₂CH₂CH₂SiMeCl₂)₃ (11), Si(OCH₂CH₂CH₂SiMe₂Cl)₄ (13) and MeSi(OCH₂CH₂CH₂SiMe(OCH₂CH₂CH₂SiMe₂Cl)₂)₃ (15) with 4a or 4b, respectively, under similar reaction conditions. Thereby MeSi[OCH₂CH₂CH₂SiMe₂OCH(Me)(CH₂)₄SiMe₂H]₃ (10), MeSi[OCH₂CH₂CH₂SiMe[OCH(Me)(CH₂)₄SiMe_3 − nH_n]₂]₃ (12a, n = 1; 12b, n = 2), Si[OCH₂CH₂CH₂SiMe[OCH(Me)(CH₂)₄SiMe₂H]₂]₄ (14) and MeSi[OCH₂CH₂CH₂SiMe[OCH₂CH₂CH₂SiMe₂OCH(Me)(CH₂)₄SiMe_3 − nH_n]₂]₃ (16) are formed as colourless oils.Compounds 3, 4, 6-8, 10, 12, 14 and 16 were characterised by elemental analysis as well as spectroscopic (IR, NMR) and mass spectrometric (ESI-TOF) studies.     

Synthesis of poly(styrene-b-dimethylsiloxane) multi-block copolymers via polyhydrosilylation reaction

Poly(styrene-b-siloxane) multi-block copolymers have been prepared by polyhydrosilylation reaction. Four copolymers have been synthesized by the reaction of α,ω-bis silane polydimethylsiloxanes with α,ω-bis allyl polystyrene. The latter has been obtained by the reaction of carboxy-telechelic polystyrene with allyl glycidyl ether. ¹H NMR and FT-IR analyses show that the polyhydrosilylation reaction is quantitative. The copolymer molecular weights were determined by SEC to be about 25,000 g/mol. The properties of these copolymers were characterized by DSC and DMA analyses. The rubbery plateaus of these copolymers are in the range of −115 °C to 85 °C.     

Hydrolytically stable linkers for silicone carbohydrates derived from hydrodiisopropylsilanes

Two strategies were developed for the attachment of sugars to siloxanes using bifunctional silicon linkers: the substrate could be functionalized with a silyl hydride before coupling to a vinyl-terminated siloxane through platinum catalyzed hydrosilylation; alternatively, unprotected glucose could be directly silylated by a silicone terminated with a chlorosilyl group. Optimal steric bulk was found with difunctional diisopropylsilanes, which exhibit excellent reactivity for preparation of sugarsilane derivatives, and also permit efficient grafting to silicones via hydrosilylation. The resulting product alkoxysilane-silicone exhibits greater stability to hydrolysis than the silicone itself.