Metal-catalyzed alcoholysis processes

Transition metals have already established a prominent role in synthetic silicon chemistry [1 - 5]. This is well illustrated by the Direct Process, which is a copper-mediated combination of elemental silicon and methyl chloride to produce methylchlorosilanes, and primarily dimethyldichlorosilane. This process is practiced on a large, worldwide scale, and is the basis for the silicones industry [6]. Other transition metal-catalyzed reactions that have proven to be synthetically useful include hydrosilation [7], silane alcoholysis [8], and additions of Si-Si bonds to alkenes [9]. However, transition metal catalysis still holds considerable promise for enabling the production of new silicon-based compounds and materials. For example, transition metal-based catalysts may promote the direct conversion of elemental silicon to organosilanes via reactions with organic compounds such as ethers. In addition, they may play a strong role in the future... 

It has been known for some years that the group VIII metals and metal salts catalyze the dehydrogenative solvolysis of hydrosilanes with amines, alcohols and carboxyhc acids [69]. Studies on the scope of these processes and the mechanistic investigations were limited to the use of monohydrosilanes. Recently, it has been found that chlorotris(triphenylphosphine)rhodium(I) (7) is exceedingly effective for the selective alcoholysis of hydrosilanes including polyhydrosilanes [33, 70]. 

Self-catalyzed esterification is often too slow to be of practical use, especially because hydroxyl-terminated polymers are either sought or are a consequence of the process (aromatic polyesterifications are carried out with a large excess of hydroxyls at the beginning of the process, because of the low solubility of the diadd), and strong protic acids are not advisable, as they would catalyze polymer hydrolysis if allowed to remain with the polymer. Even volatile catalysts such as methanesul-fonic acid are avoided. Therefore, metallic salts are currently used as catalysts, both for esterification and alcoholysis. Strong bases, such as lithium hydroxide, can also be used, but for alcoholysis only (as in polycarbonate formation). 

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