Functional group chlorosilanes

The feasibility of bonding pyridinyl groups to silicon which contains a hydrolytically sensitive functional group has recently been demonstrated 15-71. 2-Fluoro-3-(dimethylchlorosilyl)pyridine and 3-fluoro-4-(dimethylchloiosilyl)pyridine as well as 2-, 3-, and 4-(dimethylchlorosilyl)pyridine were prepared by the reaction of the corresponding lithiopyridines with excess Me2SiCl2- Hydrolysis of the pyridinyl substituted chlorosilanes gave disiloxanes which were insoluble in water. In the present report we will describe extension of this work to include pyridinyl dichlorosilanes which can be hydrolyzed to polysiloxanes. These polymers can be N-oxidized and the resultant derivatives have been shown to be effective hydrophobic transacylation catalysts. 

Silica is the most commonly used solid support. Treatment with complexes bearing alkoxy- or chlorosilane functional groups is a common way to generate supported complexes on silica or any inorganic oxide containing surface silanol (Si-OH) groups (Scheme 7.2).23,24... 

Specihc functional groups are also analyzed by chemical methods. For example, the various chlorosilanes can be hydrolyzed and the resulting chloride ions determined by... 

The most important monomers (> 95 % by weight) for silicone synthesis are the methyl chlorosilanes. Next to them are the phenyl chlorosilanes, methyl phenyl chlor-osilanes, methyltrifluoropropyl chlorosilanes, and a variety of silanes containing organic functional groups such as hydroxyl, amine, epoxy, acrylate and carboxyl which are responsible for the different products. 

Because of the low solubility of most poly silanes in combination with expandable processing, that is, purification including the above mentioned hydrolysis steps, product yields and purity are often unsatisfactory if obtained by reductive coupling of chlorosilanes. A further negative aspect of this approach is the limited functional group tolerance. Accordingly, only the synthesis of polysilanes with inert pendant groups such as alkyl or aryl can be adequately achieved. 

Several methods can be potentially used for the synthesis of functionalized symmetric stars. The chlorosilane method has been applied for the synthesis of three-arm PBd stars carrying one or two end-functional groups,70 as shown in Scheme 30. The dimethylamino end groups were later transformed to sulfozwitterions by reaction with 1,3-propane sultone. 

Aryl chlorosilanes were found to undergo palladium-catalyzed cross coupling reaction with aryl chlorides in the presence of a fluoride salt giving unsymmetrical biaryls (see Scheme 36 [129]). A variety of functional groups (cyano, acetyl, fluoro, trifluoromethyl) are tolerated in this reaction. While the... 

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