Silylamides

The analogous reaction between anhydrides and alkoxysilanes also produces acyloxysilanes. The direct reaction of acids with chlorosilanes does not cleanly lead to full substitution. Commercial production of methyltriacetoxysilane direcdy from methyltrichlorosilane and acetic acid has been made possible by the addition of small amounts of acetic anhydride or EDTA, or acceptance of dimethyltetraacetoxydisiloxane in the final room temperature vulcanising (RTV) appHcation (41—43). A reaction that leads to the formation of acyloxysilanes is the interaction of acid chlorides with silylamides. 

Lithium silylamides react smoothly with tiifluoronitrosomethane to give diazenes Traces ot water initiate the decomposition of the latter with liberation of a trifluoromethyl carbanion, which is trapped by carbonyl compounds [775] (equation 116) Desilylation of trialkyl(trifluoromethyl)silanes by fluoride ion produces also a trifluoromethyl carbanion, which adds to carbonyl carbon atoms [136, 137] (equations 117 and 118)... 

Volatile silylamides are readily prepared by reacting a silyl halide with NH3, RNH2 or R2NH in the vapour phase or in Et20, e.g. ... 

In contrast to the borylation of alkane C-H bonds, the coupling of aryl halides with amines was based on a literature precedent from another group published about a decade before our initial studies. Kosugi, Kameyama and Migita published the coupling of aryl halides with tin amides." Mechanistic studies we conducted on this process led us to the perhaps obvious realization that the reaction" could be conducted with amines and a silylamide base instead of tin amides (equation 4)." Surveys of bases with similar p a values led Janis Louie to conduct reactions with alkoxide bases. Similar studies were conducted at nearly the same time by Steve Buchwald and coworkers."... 

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. 

As noted above, KH-catalyzed polymerization of the CH3SiHCl2 ammonolysis product gives a polymeric silylamide of type [(CH3SiHNH)a-(CH3SiN)b(CH3SiHNK)e]. In a typical example, a = 0.39, b = 0.57, c = 0.04, so there is only a low concentration of silylamide functions in the polymer. This polymeric silylamide reacts with electrophiles other than... 

In an attempt to prepare polymers of type Ic or Id from acid amides and 1,3-dichlorodisiloxanes or 1,5-dichlorotrisiloxanes, it was found that bimolecular cyclization prevailed over polycondensation and cyclic bis(silylamides) in the amido (la) or imidato (lb) isomeric forms were exclusively formed in high yields... 

To summarize die effects of the nature of groups R and Y on the structure of bis(silylamides) (I) it can be concluded that relative increase of the it character in the carbon-nitrogen bond is probably responsible for the relative stabilization of the... 

These molecules can be interpreted as dimers of Li-F adducts of iminosilanes. They react like silylamides as well as like iminosilanes. 

An oxidative Mannich cyclization methodology allowed the synthesis of indolizidine skeletons. The oxidation of the a-silylamide 140 with ceric ammonium nitrate (CAN) formed in situ an iV-acylaminium cation, which cyclized to afford the bicyclic compound 141 (Scheme 35) <1998JOC841>. 

Boche and coworkers drew attention to the solid state structure of mixed amine-metal amide99 and silylamide-nitrile complexes100 as models of reaction intermediates. 

More recently, Aspinah et al. reported the synthesis of a series of lanthanide silsesquioxanes resulting from reactions of 3 with lanthanide tris(silylamides) Ln[N(SiMc3)2]3 (Ln = Y, La, Pr, Eu, Yb). However, single crystals of these materials suitable for X-ray diffraction could not be obtained. The somewhat complicated situation is illustrated in Scheme 25. The lanthanide tris(silylamides) reacted with two-third equivalents of the trisilanol 3 in THF to give the lanthanide silsesquioxanes 85, which are dimeric in solution at 233 K. Reaction of Ln[N(SiMe3)2]3 with one equivalent of 3 in THF resulted in complete conversion of 3 to the trisilylated compound 14, as did the reaction of Ln[N(SiMe3)2]3 with two-third equivalents of 3 in toluene. 

Si H M agostic interactions in silylamido complexes have been extensively studied to date. The earlier examples were prepared by halide displacement in the coordination sphere of a metal by a silylated amide, which puts severe limitations on the nature of the substituents at silicon (usually, robust methyl groups are used). More recently, a new route to p-agostic silylamides based on the direct coupling of silanes with imido ligands was discovered that allows one to trace the effect of substitution at silicon on the extent of the Si-H bond complexation (vide infra). 

The scope of nitrolysis is huge, with examples of nitramine formation from the cleavage of tertiary amines, methylenediamines, carbamates, ureas, formamides, acetamides and other amides. The deflnition of nitrolysis must be extended to the nitrative cleavage of other nitrogen bonds because sulfonamides and nitrosamines are also important substrates for these reactions. The nitrative cleavage of silylamines and silylamides is also a form of nitrolysis (Section 5.7). 

Millar and Philbin ° reported using dinitrogen pentoxide in methylene chloride at subambient temperatures for the nitrodesily lation of silylamines (33) and silylamides. The methodology, which results in nitramines (34), nitramides and nitroureas in excellent yields, is well suited for the synthesis of energetic materials and we believe it will find wide use in the future. 

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