Chlorosilanes Grignard reagent

Entry Initial chlorogermanes and chlorosilanes Grignard reagent Mole ratio of the products... 

Nevertheless Kipping made a number of contributions of value to the modem silicone industry. In 1904 he introduced the use of Grignard reagents for the preparation of chlorosilanes and later discovered the principle of the inter-molecular condensation of the silane diols, the basis of current polymerisation practice. The term silicone was also given by Kipping to the hydrolysis products of the disubstituted silicon chlorides because he at one time considered them as being analogous to the ketones. 

The use of the Grignard reagents of the type RMgX for the production of alkyl-and aryl-chlorosilanes was pioneered by Kipping in 1904 and has been for a long time the favoured laboratory method for producing these materials. 

While chlorosilanes are susceptible to hydrolysis, aryltrialkoxysilanes are not Treating the Grignard reagent generated from aryl bromide 127 with SiCL, then with a solution of pyridine in methanol furnished aryltrimethoxysilane 128 [104], Subsequent Pd-catalyzed coupling between 128 and 3-bromopyridine assembled biaryl 129 in 72% yield with the aid of TBAF. 

Their advantage over other types of dendrimers is their straightforward synthesis and, most importantly, their chemical and thermal stabilities. Two distinct steps characterize their synthesis a) an alkenylation reaction of a chlorosilane compound with an alkenyl Grignard reagent, and b) a Pt-cata-lyzed hydrosilylation reaction of a peripheral alkenyl moiety with an appropriate hydrosilane species. Scheme 2 shows the synthesis of catalysts Go-1 and Gi-1 via this methodology. In this case, the carbosilane synthesis was followed by the introduction of diamino-bromo-aryl groupings as the precursor for the arylnickel catalysts at the dendrimer periphery. The nickel centers of the so-called NCN-pincer nickel complexes were introduced by multiple oxidative addition reactions with Ni(PPh3)4. 

TABLE 32. Competing reactions of chlorogermanes and Me3GeCl or chlorosilanes with Grignard reagents in 1 1 ether-benzene"... 

The most important laboratory method of the preparation of particular organosilicon compounds is the reaction of an appropriate chlorosilane and a Grignard reagent (equation 3). 

Titanocene dichloride catalyzes the reduction of alkyl, aryl, and vinyl bromides, aryl chlorides, alkoxy- and halosilanes ketones, esters, and carboxylic acids with alkyl Grignard reagents. This Cp2TiCl2/RMgX system can also be used for the hydromagnesation of alkynes, dienes, and alkenes (Section 3.2.5). Kambe et al. have reported a new type of titanocene-catalyzed transformation with vinyl Grignard reagents and chlorosilanes to furnish l,4-disilyl-2-butenes, as shown in Scheme 3.43 [31]. 

Although chlorosilanes are the most readily available silylating reagents, their use in catalytic silylation has not yet been achieved, probably because of the difficulty of oxidative addition of the Si-Cl bonds to transition metal centers. The first example of the transition metal-catalyzed silylation of alkenes with chlorosilanes and silylsulfides, silylselenides, and silyltellurides has been reported [33]. This reaction proceeds under mild conditions with a catalytic amount of a zirconocene complex in the presence of a Grignard reagent to give alkenylsilanes and/or allyl-silanes. 

Organic functionalities can also be inserted into aminochlorooligosilanes by salt elimination with lithium or Grignard reagents. This type of reaction yields various specifically organic-substituted aminosilanes which are able to react with HCI and to form the corresponding chlorosilanes (Scheme 4). Via this reaction type different olefinic functionalized disilanes were prepared [9],... 

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