Trialkylsilanes reactions with

Hydrosilanes react with butadiene by the catalysis of palladium compounds, but the nature of the reaction is somewhat different from that of the telomerization of other nucleophiles described before. Different products are obtained depending on both the structure of silanes and the reaction conditions. Trimethylsilane and other trialkylsilanes reacted with butadiene to give the 1 2 adduct, l-trialkylsilyl-2,6-octadienes (65), in high yield (98%) (62-64). Unlike other telomers which have the 1,6-octadienyl chain, the telomers of silanes have the 2,6-octadienyl chain. As catalysts, Pd(PPh3)2 (maleic anhydride), PdCl2(PhCN)2, PdCl2, and 7r-allylpalladium chloride were used. Methyldiethoxysilane behaved similarly to give the 1 2 adduct. 

The hydrosilylation of alkenes with trialkylsilanes in the presence of Lewis acid catalysts under mild conditions gives the corresponding (trialkylsilyl)alkanes [Eq. (22)]. Reaction with terminal alkenes such as 1-hexene and 1-dodecene at room temperature gives hydrosilylation products in 57 and 58% yields, respectively. Reactions with activated styrene derivatives such as styrene, / -chlorostyrene, and a-methylstyrene at —20°C afford hydrosilylated products in 55-61% yields. ... 

Both 49 and trialkylsilanes undergo exchange reactions with trimethylhalosilanes in the presence of quinoline to give 1-halosilatranes (equation 73)16. It is likely that steric hindrance is responsible for the lack of addition of 1-hydrosilatrane (49) to the multiple bond of monosubstituted alkenes and acetylenes in the presence of H2PtCl6 or under UV... 

There have been several reports of catalytic methods for alcoholysis of trialkylsilanes,10-17 however only a few of these papers have included reactions with dialkyl(dihydrido)silanes.9a,d 15 Among the more reactive catalysts for the preparation of trialkylsilyl ethers from silyl hydrides... 

Crotyl silanes offer the possibility of diastereoselectivity in reactions with aldehydes in the same way as the corresponding boranes. The mechanism is completely different because crotyl trialkylsilanes react via an open transition state as the silicon is not Lewis acidic enough to bind the carbonyl oxygen of the electrophile. Instead, the aldehyde has to be activated by an additional Lewis acid or by conversion into a reactive oxonium ion by one of the methods... 

When an allylsilane containing a C(3) substituent reacts with an aldehyde, two new stereogenic centers are established. The reaction of ( )- and (Z)-2-butenyI-trialkylsilanes with aldehydes was first reported by Hayashi and Kumada in 1983 [28]. In these studies either ( )- and (Z)-2-butenyltrimethylsilane or ( )- and (Z)-cinnamyltrimethylsilane combined with various aldehydes in the presence of TiCl4 (Scheme 10-9). The ( )-2-butenylsilane and ( )-cinnamylsilane both afford >95 f of the syn diastereomer upon reaction with either propanal, isobutyraldehyde, or pivalaldehyde. When the Z-silanes were subjected to the same reaction conditions much lower selectivities were observed (65-72% syn selectivity). An acyclic transition structure with an antiperiplanar arrangement of double bonds was proposed to account for the diastereoselectivity observed in these reactions. A transition stmcture which includes a synclinal arrangement of double bonds may be necessary to explain the lower selectivities observed with the Z-allylsilanes. 

Montgomery and co-workers examined this three-component reaction from a mechanistic point of view (Scheme 10.8). Using a combination of cross-over experiments between EtsSiD and PrsSiH, they demonstrated that catalyst formulations involving PBus and IMes proceed largely by fundamentally different pathways. As a lack of cross-over with IMes was observed, it was concluded that the RsSi and H units in the product were mainly from a single molecule of hydrosilane. Intermediates I or II appeared the most probable in the catalytic cycle. Also, since PBus gave cross-over between EtsSiD and PrsSiH, it was postulated that the trialkylsilane would react at the end of the reaction with a transient allyl-nickalate. 

A modified stepwise hydroboration avoiding the use of lithium aluminum hydride has also been developed (Schane 23.30). It was discovered that trialkylsilane reacts rapidly with boron trihalide to form unsolvated dihaloborane. Subsequent reaction with alkenes in the presence of sufficient boron trihalide occurs rapidly at -78°C to afford alkylboron dihalides without detectable contamination by dialkylboron halides. If additional equivalents of both trialkylsilane and alkene are added, dialkylboron halides are obtained. The methodology has been successfully applied to the synthesis of l,l,I-tris(dichloroboryl)alkanes, important precursors for dicarbapentaboranes. ... 

The reaction of hydrosilanes with butadiene is different from other reactions. Different products are obtained depending on the structurelof the hydrosilanes and the reaction conditions. Trimethylsiiane and other trialkylsilanes react to give the I 2 adduct, namely the l-trialkylsilyl-2,6-octadiene 74, in high yields[67-69]. Unlike other telomers which have the 2,7-octadienyl chain, the 2,6-octadienyl chain is formed by hydrosilylation. On the other hand, the 1 I adduct 75 (l-trichlorosilyl-2-butene)is formed selectively with trichlorosilane, which is more reactive than trialkylsilanes[69]. The Reaction gives the Z form stereoselectively[70]. A mixture of the I 1 and I 2 adducts (83.5 and 5.2%) is... 

Intermolecular allylation of aldehydes with 1 -trialkylsilyl-1,3-dienes 22 in the presence of a stoichiometric amount of triethylsilane and a catalytic amount of Ni(cod)2 and PPI13 shows novel regio- and stereoselectivity (Scheme 6) [20-22], When a toluene solution of a 1-silyl-1,3-diene and an aldehyde is refluxed in the presence of trialkylsilane under the catalysis of Ni(cod)2 and PPh3, ( )-allylsilane (E)-23 is obtained exclusively. On the other hand, when the reaction is carried out in THF upon heating at 50 °C as... 

Diphenylsilane catalyzed by various salts promotes the 1,2-reduction of cinnamaldehyde.318 Cesium fluoride catalysis is particularly effective.320 It is possible to stop these reactions at the silyl ether stage.73,320 The 1,2-reduction of citral is accomplished in high yield with diphenylsilane and Wilkinson s catalyst (Eq. 262) 435 Interestingly, the trialkylsilanes, ethyldimethylsilane and triethylsilane, give high yields of the 1,4-reduction product whereas diisopropylsilane gives a 1 1 mixture of 1,2- and 1,4-reduction (Eq. 263)435... 

The hydrosilylation of butadiene proceeds with palladium compounds even in the absence of phosphines. Other ligands, such as glyoxime, benzonitrile, and 1,5-cyclooctadiene, can be used as effective ligands for the hydrosilylation of butadiene (65, 67). The reaction of trichlorosilane and dichlorosilane with isoprene proceeded regioselectively and stereo-selectively to give Z-l-trichlorosilyl-2-methyl-2-butene (67) (65, 66, 68). No reaction of trimethylsilane with isoprene took place, and this shows the lower reactivity of trialkylsilane. 

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