Silylamide-catalyzed reactions

While these silylamide-catalyzed reactions provided a good way to solve the problem of the low ceramic yield in the pyrolysis of [(CH3SiH)x (CH3Si)y]n, the problem of the elemental composition of the ceramic product remained (i.e., the problem of Si/C ratios greater than one) since only catalytic quantities of the silylamide were used. 

Scheme 19 Rare earth silylamide-catalyzed monocoupling reactions of isocyanides with terminal alkynes...

Like rare-earth metal hydride and alkyl complexes [141, 206, 207], silylamide derivahves catalyze the hydrosilylation of alkenes and dienes with phenylsilane [208-210]. Accordingly, materials [Ln N(SiMe3)2 3] AS-380.7oo (12a-d, Table 12.3) featuring monopodal bis(silylamide) surface complexes have been exploited as catalysts for the reaction of 1-hexene and styrene with PhSiH3 (Scheme 12.20) [118]. 

Table 12.10 Tishchenko dimerization reaction catalyzed by PMS-supported rare-earth metal silylamide complexes.

An alternative pathway when soluble alkoxide or silylamido bases are used, involves reaction of a palladium amido aryl complex with the alkoxide or silylamide to form an intermediate alkoxide or amide. These complexes can react with amines to form the required amido aryl intermediate. This pathway seems to occur for aryl halide animations catalyzed by complexes with chelating ligands. The inorganic... 

Four classes of catalysts have been used for the coupling of amines and related nitrogen nucleophiles witii aryl halides. Initially, complexes of the hindered monodentate aromatic tri-ortlio-tolylphosphine catalyzed the reaction of aryl bromides with secondary amines in the presence of an alkoxide or silylamide base. The use of this catalyst for this type of coupling to form C-N bonds was based on an earlier report of the reaction of aryl bromides with tin amides in the presence of a palladium complex of the same ligand as catalyst. - Later, complexes containing aromatic bisphosphines, such as BINAP and dppf, were... 

Despite significant research into new chiral carbene catalysts, few improvements in the direct asymmetric intermolecular addition of aldehydes to activated olefins have been possible. An innovative alternative was reported by Johnson and co-workers, who showed that chiral metallophosphite 31 could catalyze an asymmetric sila-Stetter reaction with high enantioselectivity. Due to the absence of a silyl scavenger, catalyst turnover occurs by a [l,4]-retro-Brook reaction, and the initially isolated a-silylamide product is recrystallized to improve the enantiomeric purity from 90 to 99% ee. Desilylation completes the three-step procedure to give y-ketoamide 32 in good yield and excellent enantiomeric purity. The reaction... 

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