Alkenes organosilanes

A catalyst, usually acid, is required to promote chemoselective and regioselective reduction under mild conditions. A variety of organosilanes can be used, but triethylsilane ia the presence of trifiuoroacetic acid is the most frequendy reported. Use of this reagent enables reduction of alkenes to alkanes. Branched alkenes are reduced more readily than unbranched ones. Selective hydrogenation of branched dienes is also possible. 

Supplemental References for Table 1. Organosilane Reduction of Alkenes... 

An alternate route to formation of alkyl monolayers is via Lewis acid catalyzed reactions of alkenes with the hydrogen terminated surface. In this approach, a catalyst such as ethyl aluminum dichloride is used to mediate the hydrosilylation reaction of an alkene (or alkyne), resulting in the same type of product as in the case of the photochemical or thermal reactions. This type of reaction is well known based on molecular organosilane chemistry and has also been used successfully to alkylate porous silicon [31]. Although this route has been shown to work on H/Si(lll), the resulting monolayers are found to have lower coverages than those achieved using the photochemical or thermal approach [29], Another concern with this approach is the possibility of trace metal residues from the catalyst that could adversely affect the electronic properties of these surfaces (even when present at levels below the detection limit of most common surface analysis techniques). 

Addition reactions of hydrosilanes to alkenes shown in the following general scheme are one of the most frequently utilized reactions for the preparation of organosilanes (equation 20). ... 

The ionic hydrogenation of carbon-carbon multiple bonds has been demonstrated only for the reduction of carbon-carbon double bonds which on protonation result in the formation of tertiary, or aryl-substituted, carbocations. The ability to use this reduction reaction with functionally substituted alkenes will be limited to those systems that do not contain functional groups that would otherwise react with trifluo-roacetic acid or the organosilane. 

Ally halides (equation 37), vinyl halides (equation 38) and vinyl ethers are good substrates for the preparation of organosilanes having functional groups at the 3- or 7-position. Reduction of these substrates sometimes takes place to give the parent alkenes (equation 37), which are derived from 3-elimi-nation of the regioisomeric hydrosilylation intermediates. ... 

In contrast to the typical palladium(0)-catalyzed cross-coupling reaction of vinyl triflates with organosilanes, this is an example of the reduction of an enone to an alkene by transfer of a proton instead of an alkyl moiety/ ... 

Transition metals have already established a prominent role in synthetic silicon chemistry [1 - 5]. This is well illustrated by the Direct Process, which is a copper-mediated combination of elemental silicon and methyl chloride to produce methylchlorosilanes, and primarily dimethyldichlorosilane. This process is practiced on a large, worldwide scale, and is the basis for the silicones industry [6]. Other transition metal-catalyzed reactions that have proven to be synthetically usefiil include hydrosilation [7], silane alcdiolysis [8], and additions of Si-Si bonds to alkenes [9]. However, transition metal catalysis still holds considerable promise for enabling the production of new silicon-based compounds and materials. For example, transition metal-based catalysts may promote the direct conversion of elemental silicon to organosilanes via reactions with organic compounds such as ethers. In addition, they may play a strong role in the future... 

Elimination of silyl groups with p-oxy groups, i.e., Peterson-type elimination, is a useful method for preparing stereodefined alkenes [101,102]. The synthetically useful allylsilanes are effectively synthesized in geometrically and enantio-merically pure forms through the Peterson-type elimination of organosilanes prepared by palladium-catalyzed bis-silylation (Eq. 57) [72, 73]. The intramolecular bis-silylation of optically active allylic alcohols in refluxing toluene af-... 

Most ir-nucleophiles employed in iminium ion cyclizations have a predetennined postcyclization destiny. For example, aromatic terminators will rearomatize, organosilanes will eliminate silicon through anticipated pathways and acetals and enol ethers will produce carbonyl compounds. However, the cyclizations of simple alkenes have supplied products that are the formal results of eliminations, additions and Wagner-Meerwein rearrangements. Almost exclusively Mannich-type cyclizations of unsaturated amines have been employed to prepare piperidines. 

---