Silanes halo

Many other reactions of ethylene oxide are only of laboratory significance. These iaclude nucleophilic additions of amides, alkaU metal organic compounds, and pyridinyl alcohols (93), and electrophilic reactions with orthoformates, acetals, titanium tetrachloride, sulfenyl chlorides, halo-silanes, and dinitrogen tetroxide (94). 

Silane forms halo derivatives with hydrogen halides. The reaction occurs moderately at ordinary temperature catalyzed by aluminum hahdes ... 

The trihalogeno-substituted silanes are very readily hydrolyzed, and the initially formed silanols condense with themselves and with halo-genosilanes with extreme ease. Consequently, few simple intermediate hydrolysis products of this class have been isolated or characterized. Linear halogen-substituted silanols and siloxanes are certainly first... 

The most common and convenient methods for the preparation of a variety of Si- and C-substituted silatranes are the reactions of trifunctional silanes with tris(2-hydroxyalkyl)amines (equation 1). Halo, alkoxy, acyloxy and dialkylamino groups can... 

The most direct procedure for the synthesis of a-haloacyl silanes is electrophilic halo-genation of enolates or enol ethers of acyl silanes. This has been achieved with the silyl enol ethers using bromine at low temperatures, but the reaction suffers from the general... 

The related Brook rearrangement of a-halo-a,jS-unsaturated acyl silanes produces silyloxy allenes (63), from which several sesquiterpenes have been synthesized (Scheme 106)21. Silyloxy allenes may also be prepared by the alkylation of silyloxy allenyl lithium reagents the acyl silane route is, however, less sensitive to solvent effects and other experimental parameters. An outline of the synthesis of dehydrofukinone (64), which elegantly exemplifies this methodology, appears in Scheme 107. 

Recently Bassindale et al. (288) discovered a new mechanism of halo-silane racemization in the presence of nucleoophiles. They performed dynamic NMR studies of the inversion at silicon catalyzed by HMPA and N-trimethylsilylimidazole, using as a model a halosilane having di-astereotopic methyl groups. Diastereotopic separation of the H- and 13C-NMR signals is apparent in both the substrate and the silylonium complex. Thus, inversion at the Si center leading to coalescence may be... 

In recent years, we have been investigating easy and economical functionalization of widely nsed carbon based polymers snch as polybntadienes. The preliminary results of these studies have led our group to discover a highly selective and mild synthetic route to silyl-functionalization of 1,2-polybutadienes (PBD) via Pt-nanocluster catalyzed hydrosilylation of olefin bonds. Unlike other catalytic systems, our system was found to be equally effective with all varieties of functional silanes such as halo-, alkyl-, aryl- and alkoxy- silanes affording high yields and selectivities. In addition, all the hydrosilylation reactions were found to be very clean with the ease of product separation and purifications (Scheme 2). 

Trichloro(methyl)silane-Sodium iodide, 11, 553-554. This in situ equivalent of io-dotrimethylsilane is also effective for cleavage of esters and lactones, selective conversion of tertiary and benzylic aleohols into iodides, dehalogenation of a-halo ketones, deoxygenation of sulfoxides, and conversion of dimethyl acetals to carbonyl compounds. ... 

Mg Si bonds have long been inferred in reactions that generate hexaorganodisilanes from halo(triorgano)silanes and either a Grignard reagent or Mg metal ( Silico-Barbier reaction). Similarly, the electrochemical reduction of chloro(triorgano)silanes with sacrificial Mg electrodes yields... 

Bromine and chlorine react with vinylsilanes to afford vinyl bromide and chloride with net inversion of configuration. Addition of these halogens proceeds with anti stereochemistry. Elimination of halo-silane in the presence of a nucleophile like F or RO also is assumed to take place in an anti manner (Scheme 16). The same transformation using iodine is applicable only to 1,2-dialkylvinylsilanes. The process is a reliable method for the preparation of vinyl halides of defined configuration. The reactions are not, overall, reductions, and they are included here only to emphasize the usefulness of the products of hydrosilylation. 

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