67416-43-7Relevant academic research and scientific papers
Markovnikov Hydrosilylation of Alkynes with Tertiary Silanes Catalyzed by Dinuclear Cobalt Carbonyl Complexes with NHC Ligation
Deng, Liang,Lai, Yuhang,Leng, Xuebing,Wang, Dongyang,Wang, Peng,Xiao, Jie
supporting information, p. 12847 - 12856 (2021/08/24)
Metal-catalyzed hydrosilylation of alkynes is an ideal atom-economic method to prepare vinylsilanes that are useful reagents in the organic synthesis and silicone industry. Although great success has been made in the preparation of β-vinylsilanes by metal-catalyzed hydrosilylation reactions of alkynes, reported metal-catalyzed reactions for the synthesis of α-vinylsilanes suffer from narrow substrate scope and/or poor selectivity. Herein, we present selective Markovnikov hydrosilylation reactions of terminal alkynes with tertiary silanes using a dicobalt carbonyl N-heterocyclic carbene (NHC) complex [(IPr)2Co2(CO)6] (IPr = 1,3-di(2,6-diisopropylphenyl)imidazol-2-ylidene) as catalyst. This cobalt catalyst effects the hydrosilylation of both alkyl- and aryl-substituted terminal alkynes with a variety of tertiary silanes with good functional group compatibility, furnishing α-vinylsilanes with high yields and high α/β selectivity. Mechanistic study revealed that the stoichiometric reactions of [(IPr)2Co2(CO)6] with PhCCH and HSiEt3 can furnish the dinuclear cobalt alkyne and mononuclear cobalt silyl complexes [(IPr)(CO)2Co(μ-ν2:ν2-HCCPh)Co(CO)3], [(IPr)(CO)2Co(μ- ν2:ν2-HCCPh)Co(CO)2(IPr)], and [(IPr)Co(CO)3(SiEt3)], respectively. Both dicobalt bridging alkyne complexes can react with HSiEt3 to yield α-triethylsilyl styrene and effect the catalytic Markovnikov hydrosilylation reaction. However, the mono(NHC) dicobalt complex [(IPr)(CO)2Co(μ- ν2:ν2-HCCPh)Co(CO)3] exhibits higher catalytic activity over the di(NHC)-dicobalt complexes. The cobalt silyl complex [(IPr)Co(CO)3(SiEt3)] is ineffective in catalyzing the hydrosilylation reaction. Deuterium labeling experiments with PhCCD and DSiEt3 indicates the syn-addition nature of the hydrosilylation reaction. The absence of deuterium scrambling in the hydrosilylation products formed from the catalytic reaction of PhCCH with a mixture of DSiEt3 and HSi(OEt)3 hints that mononuclear cobalt species are less likely the in-cycle species. These observations, in addition to the evident of nonsymmetric Co2C2-butterfly core in the structure of [(IPr)(CO)2Co(μ- ν2:ν2-HCCPh)Co(CO)3], point out that mono(IPr)-dicobalt species are the genuine catalysts for the cobalt-catalyzed hydrosilylation reaction and that the high α selectivity of the catalytic system originates from the joint play of the dicobalt carbonyl species to coordinate alkynes in the Co(μ- ν2:ν2-HCCR′)Co mode and the steric demanding nature of IPr ligand.
Waste-free and efficient hydrosilylation of olefins
Pandarus, Valerica,Ciriminna, Rosaria,Gingras, Geneviève,Béland, Fran?ois,Kaliaguine, Serge,Pagliaro, Mario
, p. 129 - 140 (2019/01/11)
High purity silicone precursors can now be synthesized by hydrosilylation of solvent-free olefins catalyzed by a highly stable and active glass hybrid catalyst consisting of mesoporous organosilica microspheres doped with Pt nanoparticles. These findings open the door to the sustainable manufacture of silicone and a way to further reduce the amount of platinum in silicones, which are ubiquitous advanced polymers with multiple uses and applications.
On the regioselectivity of palladium catalyzed cross-coupling reactions of alkenylsilanes: participation of β-cationic organosilicate-palladium species during the transmetallation
Hatanaka, Yasuo,Goda, Ken-ichi,Hiyama, Tamejiro
, p. 97 - 100 (2007/10/02)
The cross-coupling reaction promoted by a palladium catalyst and fluoride salt of 1--1-phenylethene (1) with substituted aryl iodides gave the unexpected cine-substitution products (E)-1-aryl-2-phenylethenes (3) along with the normal ipso-substitution product 1-aryl-1-phenylethene (2).The product ratios were strongly dependent on the electronic nature of the substituent on aryl iodides: ipso-substitution products (2) were favoured by an electron-withdrawing substituent, and cine-substitution products (3) by an electron-donating substituent.On the basis of these observations, the following mechanism of transmetallation of alkenyl(fluoro)silicates with arylpalladium is proposed: electrophilic attack of an arylpalladium complex on the olefinic α-carbon of an alkenyl(fluoro)silicate produces a β-cationic organosilicate-palladium species which then transfers the alkenyl group from silicon to the palladium complex. Key words: Silane; Palladium; Transmetallation; Regioselectivity
1H, 13C and 29Si NMR study of α- and β-silylstyrenes and their adducts with dichlorocarbene
E. Liepins,Goldberg, Yu.,Iovel, I.,Lukevics, E.
, p. 301 - 312 (2007/10/02)
1H, 13C and 29NMR spectra for the α- and β-silylstyrenes (E)-PhCH=CHSiR3 (I) and PhC(SiR3)=CH2 (II) (R = Cl, Me, Ph), and those for some dichlorocarbene adducts of I and II (R = Me, Ph), were examined.From the 13C NMR data, the phenyl substituent in the m
