Silylamines synthesis

Millar and Philbin have explored the nitrodesilylation of silylamines with dinitrogen pen-toxide for the synthesis of nitramines and their derivatives. These reactions, which involve nitra-tive Si-N heteroatom cleavage, are conducted in methylene chloride at subambient temperature. Trimethylsilylamines give high yields of nitramine product and reactions are clean (Table 5.8). 

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. 

Essentially all of the classical methods for the synthesis of organic amines can be successfully applied to the synthesis of a-silylamines. However, the lack of good general methods for the preparation of halomethylsilanes remains a serious drawback. 

Ring opening of 2-silylaziridines synthesis of p-silylamines and a-silyl-p-aminoalcohols... 

Silylamido groups are used throughout the periodic table to stabilize unusual types of bonding, coordination numbers and oxidation states. Lithium silylamides, generally prepared by reaction of the silylamine with alkyl- or aryllithium derivatives, play an important role in the synthesis of such molecules. 

Isocyanates and isothiocyanates both react with water in a manner similar to the halosilanes to give hydrated silica. They also react with primary and secondary amines to give silylamines which, on hydrolysis, afford A-mono- and N,N-disubstituted ureas and thioureas (Scheme 31), which is a useful synthesis of these compounds. ... 

A further method for the synthesis of the title compounds with only hydrogen as byproduct is the base-catalyzed dehydrogenative coupling (index D) of ammonia and tris(hydridosilylethyl)boranes, B[C2H4Si(R)H2]3 (R = H, CH3). Initially, the strong base, e.g. n-butyl lithium, deprotonates ammonia. The highly nucleophilic amide replaces a silicon-bonded hydride to form a silylamine and lithium hydride, which then deprotonates ammonia, resuming the catalytic cycle. Under the conditions used, silylamines are not stable and by elimination of ammonia, polysilazane frameworks form. In addition, compounds B[C2l-L Si(R)H2]3 can be obtained from vinylsilanes, H2C=CHSi(R)H2 (R - H, CH3), and borane dimethylsulfide. 

Ceric ammonium nitrate (CAN) and ceric tetrabutylammonium nitrate (CTAN) [40-42, 240] oxidation of a-silylamine and a-silylamide have been utilized for the synthesis of hydropyridines (Scheme 31). 

Recently Le Gall et al. have been able to bring about regio- and diastereo-selective synthesis of a-cyanoamines by anodic oxidation of cyclic a-silylamines (Scheme 44) [267],... 

The hydrosilylation of imines giving N-silylamines is synthetically valuable, not only because it provides a convenient route to A-silylamines, which are known as useful reagents for organic synthesis, but also because it is a new and effective method for the reduction of imines ... 

B-Fluoroborazines have also been prepared by elimination of silyl fluorides. Facile cleavage of the Si—N bond renders silylamines very effective in the synthesis of these and other B-haloborazines, and they are extensively utilized. Reactions involving elimination of silyl halides have been found particularly useful in sterically hindered systems. ... 

The high acid and moisture sensitivity of silylamines has been a major obstacle to their use in amino group protection. Primary amines have been protected as their rerr-butyidiphenylsilyl derivatives whose steric bulk militates against further reaction to form an Af,N-disilylamine. rerr-Butyldiphenylsilylamines have remarkable stability towards strongly basic conditions (e.g., 20% potassium hydroxide in refluxing methanol), but they cannot even withstand brief exposure to 80% acetic acid at room temperature. If silylamines are used at all in synthesis, they are usually prepared under anhydrous conditions, and used for one or two steps before their flimsy services are dispensed with. 

Nitramines can be obtained by nitrodesilylation of silylamines which can provide a route for the synthesis of certain nitramines heretofore unobtainable by conventional nitration methods. 2-Isopropyl-l,4-dinitioi dazole was synthesized by nitration of the corresponding silylated derivative [154]. 

Le Gall E, Hurvois JP, Sinbandhit S (1999) Regio-and diastereoselective synthesis of a-cyanoamines by anodic oxidation of 6-membered a-silylamines. Eur J Org Chem 1999 2645-2653... 

The insoluble pol3nner support is synthesized from silica gel and an appropriately derivatized deoxynucleoside. We routinely start with high performance liquid chromatography (HPLC) grade silica gel as a support matrix.The initial synthesis step involves refluxing 3-aminopropyl triethoxysilane with silica gel in dry toluene for 3 h to form the silylamine. This derivatized silica gel is then allowed to react with an appropriately protected nucleoside containing a 3 -p-nitrophenyl-succinate ester. The product is the nucleoside covalently linked to the support (compounds la-d). 

Synthesis of Primary Amines. iV,iV-Bis(trimethylsilyl)-methoxymethylamine, formally a +CH2NH2 equivalent, is obtained in high yield by treating chloromethyl methyl ether with LHMDS. Treatment of the bis-silylamine with organometallic reagents followed by mild solvolysis gives primary amines in good to excellent yield (eq 12). ... 

Enamine and Silyl Enol Ether Preparation. Both enamines and silyl enol ethers are useful intermediates in organic s)fnthe-sis. Aldehydes and ketones can be transformed into enamines via treatment with 2-3 equiv of trimethylsilyldiethylamine in the presence of a trace of / -toluenesulfonic acid. The presence of excess silylamine obviates the normal requirements for water removal by azeotropic distillation or by addition of an insoluble drying agent. No solvent or heating is required for the transformation, and the reaction normally proceeds at room temperature. However, heating the reaction mixture allows enamine synthesis in equally high yield without an acid catalyst. 

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