Organosilicon amines

Keywords carbofunctional organosilicon amines, hydrolysis, reetherification... 

Summary The alkoxy group reactivity in carbofunctional organosilicon amines H2NR Si(OR)3 in hydrolytic and reetherification reactions was studied. Modeling calculations of electronic and molecular parameters and thermodynamic functions of organosilicon amines were performed by computer chemistry methods. The obtained calculated parameters of the molecules agree with experimental kinetic data in terms of alkoxy group reactivity of carbofunctional aminoalkylalkoxysilanes. 

The radiochromatographic analysis of the products of reactions of methyl cations with diisobutylamine, isobutylaminotrimethylsilane and hexamethyldisilazane has shown that the reaction mechanism which includes two competitive channels is also operative in the case of organosilicon amines. 

In order to raise the solubility of organosilicon amines and their derivatives in water, their... 

Scheme 1. Re-esterification of organosilicon amines by ethyl cellosolve, where R = (CH2)3- for Vla-IXa, VIc-IXe ...

The polymerizations initiated by HMDS and N-TMS amines usually complete within 24 h at ambient temperature with quantitative monomer consumption. These polymerizations in general are slower than those mediated by Deming s Ni(0) or Co (0) initiators (about 30-60 min at ambient temperature) [19, 24, 25], but are much faster than those initiated by amines at low temperature or using amine hydrochloride initiators [20]. These HMDS and N-TMS amine-mediated NCA polymerizations can also be applied to the preparation of block copolypeptides of defined sequence and composition [22]. This organosilicon-mediated NCA polymerization, which was also shown by Zhang and coworkers to be useful for controlled polymerization of y-3-chloropropanyl-L-Glu NCA [43], offers an advantage for the preparation of polypeptides with defined C-terminal end-groups. 

The electrooxidation of organosilicon compounds containing heteroatoms has been investigated extensively and various synthetic applications have been developed. Cooper and Owen studied the oxidation potentials of a series of silyl-substituted amines, phosphines, and sulfides, and observed that silyl substitution at the carbon adjacent to the heteroatom caused a significant decrease in the oxidation potentials (Table 4) [35]. 

Reaction with Further Electrophiles of Group IVA (Sl,Ge,Sn). IV-Silylated aziridines can be prepared from ethyleneimine by amination of chlorosilanes in the presence of an HC1 acceptor, by dehydrocondensation with an organosilicon hydride or by cleavage of a silicon—carbon bond in 2-furyl-, 2-thienyl-, benzyl-, or allylsilanes in the presence of an alkali metal catalyst (262—266). N-Silylated aziridines can react with carboxylic anhydrides to give acylated aziridines, eg, A/-acetylaziridine [460-07-1] in high yields (267). At high temperatures, A/-silylaziridines can be dimerized to piperazines (268). Aldehydes can be inserted... 

As an organosilicon component for the reaction shown in equation 1, trial-koxysilanes are used predominantly since these are widely available. The transetherihcation of phenyltriethoxysilane and tetraethoxysilane with triethanolamine [tris(2-hydroxyethyl)amine, THEA] in the presence of the basic catalyst has led to the first silatranes (equation 2)1,32. 

Cleavage of the Si-C bond has gained tremendous importance in organic synthesis because of the diversity of the reactions in which organosilicon compounds can be engaged and the very mild conditions of these reactions.319 In some instances, total or partial desilylation is observed as a side or unexpected reaction. For instance, attempted cuprous ion-catalyzed insertion of trimethylsilylmethylisocyanide into the O-H bond of alcohols fails and desilylation occurs whereas insertion in the N-H bond of amines takes place in high yield (see Section IV.D.l.a).292... 

It results in the formation of the corresponding borazinyl-N-alkyl-amine-boranes [BH3(CH3)2N(CH2)3NBH]3 when the reaction is carried out with only 6 molar equivalents of the diamine. Aromatic diamines have also been used in this synthesis 103>. Borazines with N-organosilicon substituents have been obtained by reacting silicon-containing nitriles, for example, 4-cyano-2,2,6,6-tetramethyl-2,6-disilatetrahydropyrane, with NaBH4 and BF3 in tetrahydrofuran. 

In spite of the known phases, the advantage of suggested selective immovable phase is the possibility of selective analysis of various classes of organic and organosilicon compounds. Of spe-cial attention should be peculiarity of the phase to separation of cyclic and naphthene hydrocarbons, amines and alcohols with preservation of high thermal stability. 

Summary Precursor-derived quaternary Si-B-C-N ceramics frequently possess an enhanced thermal stability compared to SiC, SisN4 or Si-C-N ceramics. The stability of the materials towards crystallization and/or decomposition is directly coimected to the molecular structure and the elemental composition of the polymeric precursors. This paper highlights recent investigations on the synthesis of boron-modified polysilazanes and polysilylcarbodiimides. Hydroboration of polyvinylsilazanes and dehydrocoupling reactions of boron-modified silanes with ammonia or amines as well as cyanamide are described. It is shown that simple organosilicon chemistry provides a means to efficiently optimize ceramic yields and tune elemental composition as well as thermal properties of the polymer-derived ceramics. 

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