From vinylsilanes

Epoxides derived from vinylsilanes are converted by mildly acidic conditions into ketones or aldehydes.148... 

Lithium aluminum hydride-Hexa-methylphosphoric triamide, 159 Methoxyamine, 177 Titanium(III) chloride-Diisobutyl-aluminum hydride, 303 Trimethylsilyl chlorochromate, 327 From vinylsilanes m-Chloroperbenzoic acid, 76 Miscellaneous methods to prepare ketones... 

Convenient procedures for the synthesis of 1-nitro vinylsilanes 142 from vinylsilanes have been developed (equation 118)210. Similarly, nitration of allylsilane at the /-position... 

Overman and Blumenkopf prepared various seven- to nine-membered rings starting from vinylsilane 238 which was condensed with various acetals (Scheme 13.86) [56, 98, 99]. The desired medium-sized rings were obtained in moderate to good yields. 

A further method for the synthesis of the title compounds with only hydrogen as byproduct is the base-catalyzed dehydrogenative coupling (index D) of ammonia and tris(hydridosilylethyl)boranes, B[C2H4Si(R)H2]3 (R = H, CH3). Initially, the strong base, e.g. n-butyl lithium, deprotonates ammonia. The highly nucleophilic amide replaces a silicon-bonded hydride to form a silylamine and lithium hydride, which then deprotonates ammonia, resuming the catalytic cycle. Under the conditions used, silylamines are not stable and by elimination of ammonia, polysilazane frameworks form. In addition, compounds B[C2l-L Si(R)H2]3 can be obtained from vinylsilanes, H2C=CHSi(R)H2 (R - H, CH3), and borane dimethylsulfide. 

The gaseous nature of the starting monomer, vinylsilane, requiring an autoclave for polymerization, causes some difficulty in targeted polymer production on a small scale. Such a synthesis procedure, however, is analogous to polyethylene or polypropylene production. Therefore PVS directly derived from vinylsilane is potentially promising for large-scale production and widespread use in industry. 

Scheme 3. Dilithiovinylsilanes 15 and 19 from vinylsilanes by repetitive lithium addition and lithium hydride elimination.

Several secoartemisinins, illustrated by (272), have been assembled from vinylsilane (269) (Scheme 38) <90CC1487>. Ozonation and treatment with Amberlyst-15 generate successively the dioxetane (270) and the hydroperoxy-aldehyde (271). Condensation of the latter with acetaldehyde, followed by lactonization, affords (272). 

Vinyl anions derived from vinylsilanes have continued to develop as useful synthons. The lithio derivative (201), prepared by lithium-bromine exchange shows an excellent level of stereointegrity if kept below 0°C and reacts with a wide range of electrophiles. The organomagnesium derivative (202) was also examined but this anion shows a higher propensity towards E/Z isomerisation.176 Configuration instability is a drawback to the use of anions such as (201) and... 

Olefins from vinylsilanes. This reaction is generally conducted with HCl, HBr, HI, or CF3SO2OH. The cleavage with HI proceeds with retention of configuration (6, 281). Biichi and Wiiest have found that />-toluenesulfinic acid is usually very effective for this reaction, which is conducted in moist acetonitrile. Catalytic amounts of the acid suffice if the reaction is conducted at reflux. This cleavage is not stereospecific. 

Vinyl halides. These compounds can be prepared from vinylsilanes by halogenation followed by elimination of ClSi(CHa)3 with sodium methoxide or neutral alumina. 

Systems and conditions that proceed cleanly by route c (Scheme 6.62) are efficient for catalytic dehydrogenative silation. A M-SiRs source is necessary and this can be a silane, with concomitant reduction of the alkene to give an alkane (Scheme 6.62, c). /l-SiRa elimination has been artfully used to produce a M-SiRs moiety from vinylsilanes or allylsilanes. Scheme 6.63 depicts the use of allylsilanes described by Murai et ai. to produce silyl substituted alkenes and propene as byproduct [194b]. 

The present oxygenation reaction catalyzed by cobalt(II) complex with the combined use of molecular oxygen (Oxidant) and 2-propanol (Reductant) was also applied to several oxidation reactions as secondary alcohols into ketones, the direct preparation of ketones from vinylsilanes, and stereoselective oxidative cyclization of 5-hydroxyalkenes into tetrahydrofuran derivatives.il... 

HYBRIDS WITH BINARY SKELETONS OF C-C AND Si-O-Si Hybrids from Vinylsilanes or Other Bifunctional Silanes... 

The formylation reaction can be used to prepare ( )-a,p-unsaturated aldehydes from vinylsilanes by ipso substitution (eq 41). Regioselectivity in alkylation reactions may depend on the Lewis catalyst. In a fluorene, regioselective 1,8-chloromethylation results with TiCU (eq 42). TiCU aetivates... 

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