Silicon compounds coupling reactions

Substituted aroyl- and heteroaroyltrimethylsilanes (acylsilanes) are prepared by the coupling of an aroyl chloride with (Me3Si)2 without decarbonylation, and this chemistry is treated in Section 1.2[629], Under certain conditions, aroyl chlorides react with disilanes after decarbonylation. Thus the reaction of aroyl chlorides with disilane via decarbonylation is a good preparative method for aromatic silicon compounds. As an interesting application, trimel-litic anhydride chloride (764) reacts with dichlorotetramethyidisilane to afford 4-chlorodimethylsilylphthalic anhydride (765), which is converted into 766 and used for polymerization[630]. When the reaction is carried out in a non-polar solvent, biphthalic anhydride (767) is formed[631]. Benzylchlorodimethylsilane (768) is obtained by the coupling of benzyl chloride with dichlorotetramethyl-disilane[632,633]. 

In contrast to the transition metals, where there is often a change in oxidation level at the metal during the reaction, there is usually no change in oxidation level for boron, silicon, and tin compounds. The synthetically important reactions of these three groups of compounds involve transfer of a carbon substituent with one (radical equivalent) or two (carbanion equivalent) electrons to a reactive carbon center. Here we focus on the nonradical reactions and deal with radical reactions in Chapter 10. We have already introduced one important aspect of boron and tin chemistry in the transmetallation reactions involved in Pd-catalyzed cross-coupling reactions, discussed... 

Higher silicon hydrides with Ge, e.g. Si2H5GeH3 and other compounds produced in these pyrolysis reactions, have also been obtained by hydrolysis of Mg or Ca germanide-silicides446, 475, 636 and have been separated by gas chromatography446, 447. P and As derivatives produced by pyrolysis also be obtained in coupling reactions ... 

In the silylative coupling reactions of olefins and dienes with vinylsubsti-tuted silanes, ruthenium catalysts, containing initially or generating in situ Ru-H/Ru-Si bonds, catalyze polycondensation of divinylsubstituted silicon compounds to yield unsaturated silylene (siloxylene, silazanylene)-vinyl-ene-alkenylene (arylene) products (Eq. 112). For recent results see Refs. [177, 178] and for reviews see Refs. [6,7,117,118]. 

While platinum and rhodium are predominantly used as efficient catalysts in the hydrosilylation and cobalt group complexes are used in the reactions of silicon compounds with carbon monooxide, in the last couple of years the chemistry of ruthenium complexes has progressed significantly and plays a crucial role in catalysis of these types of processes (e.g., dehydrogenative silylation, hydrosilylation and silylformylation of alkynes, carbonylation and carbocyclisation of silicon substrates). 

The sodium condensation reaction of a,co-bis(chlorosilyl)-substituted compounds and the coupling reaction of dilithio derivatives of compounds bearing 7t-electron systems with dichlorosilanes offer a convenient route to various silicon containing polymers. However, the polymers prepared by these methods always contain a small proportion of siloxy units in the polymer backbone, which would interrapt the electron delocalisation. Therefore, new synthetic routes to organosilicon polymers have been developed in which no alkali metal halide condensations are involved [6, 7]. We report syntheses of organosilicon... 

The hydrolysis of (EtO)4Si (and the snbseqnent polycondensation of Si OH containing molecnles) has been the snbject of considerable investigation because of its importance in the fabrication of glasses and colloidal silica via the sol gel process (see Sol-Gel Synthesis of Solids). Hydrolysis of the Si-0 bond in alkoxysilanes is also very widely used to attach silicon compounds to surfaces and in coupling reactions. 

Wurtz coupling reactions of chlorosilanes are the main route to the silicon-silicon bonded compounds. For example, hexamethyldisilane can be prepared by refluxing trimethylchlorosilane with lithium sand in THF (97%). Lithium may be substituted by sodium by using a mixture of HMPA-THF as the solvent. Linear and branched oligosilanes can be prepared by the same method (equations 55-57). 

The silylative coupling reaction of l,2-bis(dimethyIvinylsiloxy)ethane was effectively catalyzed by 1 mol% of ruthenium hydride catalyst, and the divinyl compound was completely consumed within 1 h at 80 °C. The reaction successfully proceeded without the solvent under air, but toluene could also be employed without affecting either the activity of the catalyst or the selectivity of this process. Application of this catalytic system for silylative coupling cyclization of l,2-bis(dimethyl-vinylsiloxy)ethane gave exclusively a cyclic product (Isolated yield 85%) with the exo-methylene bond between two silicon atoms in the molecule (2,2,4,4-tetramethyl-3-methylene-l,5-dioxa-2,4-dlsilacycloheptane) accompanied only by trace amounts of oligomers. 

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