Silicon-functionalized olefins

Catalytic Carbon-Carbon Hydrogenation of Silicon-Functionalized Olefins... 

Summary From catalytic hydrogenation of olefinic silicon-functionalized compounds (chloro-Si, alkoxy-Si, alkyl-Si, and aryl-Si) the saturated products are available in good yield. In general, the chloro- and alkoxy substituents are unaffected and for silaheterocyclic compounds the cyclic or the bicyclic moieties, respectively, remain intact. Thus, the silanorbomenes 1, 2, and 3, compounds containing cyclopentenyl groups 13 and 15, and various carbon vinyl substituted silacyclobutanes 7, 8, and 11 were hydrogenated in a simple apparatus. The reactions were performed in ether and THF as solvents the hydrogenation catalyst Pd/C can be used several times. 

Silylformylation of olefins and alkynes can be regarded as the silicon version of hydroformylation. The reaction involves the concomitant introduction of a silyl group, derived from a hydrosilane, and a formyl group derived from insertion of carbon monoxide, thus producing functionalized olefins and dienes, which are useful synthons. ... 

The dependence of release force on the flexibility of the release layers is noted in systems other than silicones. Recent work in olefin release shows that release is a strong function of the density or crystallinity of the layer [44], At a density above 0.9 g/cm release for an acrylate PSA is greater than 270 g/cm. However, when the density of PE is dropped to 0.865 g/cm-, the release force of the same adhesive construction drops to 35 g/cm. An investigation of interfacial friction and slip in these systems has not yet been reported, but again the manipulation of release rheology greatly impacts the measured peel force. 

This isomerization was used in the heteroconjugate addition to the acyclic system. Therefore, the substituted olefin 72, in which the double bond is conjugated with both sulfone and silicon atoms, undergoes a diastereoselective addition of CHsLi. The resulting lithium alcoholate is quantitatively converted into the silyl ether dianion 73 and the addition of deuterium oxide afforded the functionalized product 74 in excellent yield (equation 16. 

Heteroatoni groups such as boron or silicon can activate or direct synthetic reactions. Use of such activation has become of major importance in organic syntheses. Examples in this volume are BORANES IN FUNCTIONALIZATION OF DIENES TO CYCLIC KETONES BICYCLO[3.3.1]NONAN-9-ONE and BORANES IN FUNCTIONALIZATION OF OLEFINS TO AMINES 3-PINANAMINE. Use of trimethylsilyl or trimethyl-silyloxy groups to activate a 2-butenone or a butadiene are illustrated by the preparations 3-TRIMETHYLSILYL-3-BUTEN-... 

A similar effect is observed with silicone elastomers prepared with the co-cure method the surfaces are hydrophobic and deficient in PEO, because PDMS and PHMS constituents are directed to the air interface. Interestingly, in this case, however, the silicones partition differently at the surface. ATR-FTIR demonstrated a relative increase in SiH functionality over PDMS when compared to the control. These results can only be explained by preferential migration of SiH polymer to the surface when sequestering PEO in the interior, perhaps as a result of the reduced steric bulk of each monomer unit. The resulting inside out elastomers with a hydrophilic interior and a SiH rich exterior may offer a potential route to asymmetrically structured siloxanes by subsequent reactions with other olefinic groups. 

Oxiranes of terminal monosubstituted and internal disubstituted olefins do not undergo the isomerization under standard conditions, but give aldehydes at elevated temperature. For the special substrates described in Sch. 35, different modes of reaction originated from intermediary carbocationic species, involve neighboring functional group participation, oxidation, etc. An improvement employing other silicon Lewis acids, for example Mc3SiI and McsSiBr, was developed by Kraus, Detty, and Sakurai [17,19f,62]. 

Numerous complexes of nickel(II) and nickel(O) catalyze the addition of the Si-H bond to olefins. Among such catalysts are nickel-phosphine complexes, e.g., Ni(PR3)2X2 (where X=C1, I, NO3 R=alkyl and aryl), Ni(PPh3)4, and Ni-(CO)2(PPh3)2, as well as bidentate complexes of NiCl2-(chelate) and Ni(acac)2L (I phosphine), and Ni(cod)2(Pr3)2 [1-5]. A characteristic feature of nickel-phosphine-catalyzed olefin hydrosilylation is side reactions such as H/Cl, redistribution at silicon and the formation of substantial amounts of internal adducts in addition to terminal ones [69]. Phosphine complexes of nickel(O) and nickel(II) are used as catalysts in the hydrosilylation of olefins with functional groups, e.g., vinyl acetate, acrylonitrile [1-4], alkynes [70], and butadiynes [71]. 

In the previous section one of the two major aspects of silicon syntheses was described. A major problem for the organosilicon chemist is producing a silicon-carbon bond. A second synthetic area involves functional-group transformations. Most useful reactions at silicon centers are substitution processes. This is an important difference between the chemistry of silicon compounds and that of carbon compounds. The synthetic or reaction processes in organic compounds are increased enormously by the availability of double bonds present in olefins and carbonyl derivatives. In fact, substitution at sp3-carbon centers may represent the least interesting of organic reactions. 

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