Vinyl siliconates, cross-coupling

It is a palladium-catalyzed cross-coupling reaction between organosilanes (vinyl, ethynyl and allylsilanes) and organic halides (aryl, vinyl and allyl halides). Allylpal-ladium chloride dimmer [( ri -C3H5PdCl)2] and either tris(diethylamino)sulfonium difluorotrimethylsilicate (TASF) or tetra-n-butylammonium fluoride (TBAF) are used as catalysts. Fluoride ion acts as an activator for the coupling, forming an intermediate hypervalent anionic silicon species, which can then transmetallate with palladium as a preliminary reaction to coupling. 

The same reaction conditions were applied to the coupling reaction of Trimethyl(vinyl)silane [Eq.(3)] with limited success [3], Thus, the mechanism of these silicon-based reactions appears to be different from those of the cross-coupling reactions using the main-group metal reagents. 

We sought to examine the enzymatic dioxygenation of aryl silanes using a number of different aromatic dioxygenases in order to determine if such transformations were possible and to define the substrate-specificity profile. We were also motivated by the rich chemistry of silicon-based materials, which includes the hydrosilylation of alkenes and ketones, the addition of electrophiles to vinyl and allyl silanes, and palladium catalyzed cross-coupling of vinyl silanes with aryl halides (13). As a result, silyl functional cw-diols have potential as chiral intermediates for drug development, as polymer precursors/modifiers and as elements in non-linear optical materials. 

Silylative Coupling and Cross-Metathesis of Alkenes and Dienes with Vinyl-Silicon Derivatives — New Catalytic Routes to Synthesis of OrganosUicon Compounds ... 

Summary Recent achievements in two catalytic reactions, i.e., silylative coupling and cross-metathesis of alkenes and dienes with vinyl-silicon compounds, which resulted in new synthetic routes to organosilicon molecular and macromolecular compounds are presented. The silylative coupling, also called dehydrogenative or trans-silylation and silyl group transfer, is catalyzed by metal complexes which either contain or initiate the formation of M-H and M-Si bonds, where M = Ru, Rh, Co and Ir. Cross-metathesis, which was developed very recently, proceeds in the presence of metallacarbenes, mainly those of rathenium (e.g., Grabbs catalyst). 

With the discovery of the Hiyama reaction other cross-coupling partners such as organosilicon derivatives have recently emerged as excellentreagents. 75 Various silicon substituted derivatives are suitable for transmetallation step when fluoride ions are added in the reaction medium. Organofluorosilanes bearing aryl, vinyl, or... 

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