Silylations trimethylsilyldiethylamine

SCHMIDT DEGRADATION Sodium azide. SILYLATION Trimethylsilyldiethylamine. SIMMONS-SMITH REAGENT, which see. SOMMELET REACTION Hexamethylenetetramine. 

Me3SiNEt2- Trimethylsilyldiethylamine selectively silylates equatorial hydroxyl groups in quantitative yield (4-10 h, 25°). The report indicated no reaction at axial hydroxyl groups. In the prostaglandin series the order of reactivity of trimethylsilyldiethylamine is Cii > Ci5 C9 (no reaction). These trimethylsilyl ethers are readily hydrolyzed in aqueous methanol containing a trace of acetic acid. The reagent is also useful for the silylation of amino-acids. ... 

Treatment of the allylic sulfoxide 1227 a with diisopropylethylamine (DIPEA) or of 1227 b with N-trimethylsilyldiethylamine 146 and TMSOTf 20 leads in ca. 90% yield to the quaternary amino derivatives 1228 and 1229 and HMDSO 7 [36] (Scheme 8.15). Tetramethylene sulfoxide 1230 reacts with silylated thymine 1231 in the presence of three equivalents of TMSOTf 20 to give the 4 -thio-nucleoside analogue 1232 and HMDSO 7 [37]. Other silylated pyrimidine, pyridine, and purine bases react analogously with cyclic sulfoxides to give 4 -thio-nucleoside analogues [37, 37a, 38]. 

There are rarely more than eight alkaloids present in a species, and the possibility of the same GC retention time is not normally a problem. In cases where overlap has been observed it has proved possible to identify both components from the mass spectrum of the mixture. The crude alkaloid extracts are treated with trimethylsilyldiethylamine to form volatile TMS derivatives of the hydroxylated components. The presence of a free phenolic or hydroxyl group is then detected by an ion with m/e 73 [(CH3)3Si+]. Positional isomers [e.g., erysovine (5) and erysodine (7)] are resolved although a- and /1-erythroidine are not. The presence of fi-erythroidine (60) can be estimated since it shows some enol content under the silylation conditions and gives rise to a monotrimisyl derivative with m/e 345 (15). 

N-Trimethylsilyldiethylamine (TMSDEA) is a strongly basic silylating reagent and is particulady usehil for derivatizing low molecular weight acids. The reaction by-product, diethylamine, is volatile enough to be easily removed from the reaction medium. 

Trimethylpyridine, 61, 62 N-Trimethylsilylamides, 204 Trimethylsilyl azide, 276, 542 Trimethylsilylcarbene, 544 Trimethylsilyl cyanide, 542-543 Trimethylsilyldiazomethane, 543-544 Trimethylsilyldiethylamine, 544-545 Trimethylsilyl enol ethers, 125, 538 N-(Trimethylsilyl)glycine trimethyl silyl... 

Typical vapor phase silylating agents used in top surfaee imaging systems include dimethylsilyldimethylamine (DMSDMA), trimethylsilyldimethylamine (TMSDMA), and trimethylsilyldiethylamine (TMSDEA). Typical liquid phase silylating agents used in top surfaee imaging systems inelude 1,1,33,5,5-hexamethylcyclotrisilazane and bis(dimethylamino)dimethylsilane with N-methyl-2- pyrrolidone (NMP) as a diffusion promoter. Typical polymer resins include polyvinyl phenol and novolac/diazoquinone polymer resins. 

Preparation of Phosphonic Acid Chlorides. Disilyl esters of phosphonic acids react with oxalyl chloride-DMF to give the phosphonyl chlorides and silyl chlorides under mild conditions (eq (>) Prior treatment of an acid-sensitive phosphonate monoester with Trimethylsilyldiethylamine was used to minimize exposure to HCl (eq 7). ... 

Conjugate Addition. Conjugate addition of trimethylsilyl diethylamine to enones gives /3-amino silyl enol ethers. Thus, in the presence of catalytic amounts of trimethylsilyl triflate, trimethylsilyldiethylamine adds to ethyl vinyl ketone in a 1,4-fashion. The reaction requires 50 mol % excess of trimethylsilyldiethylamine, and proceeds in ether at room temperature under nitrogen. The product Af,A -diethyl-3-[(tiimethylsilyl)oxy]-( )-2-pentamine is distilled out under reduced pressure in 45% yield (eq 18). The major product is the -enol ether containing approximately 5% of other trimethylsilyl ether isomers. 

Silylation of Amines. While there are several effective methods for preparation of Af-(trimethylsilyl)amines, only a few successful procedures for Af,Af-bis(trimethylsilyl)alkylamines synthesis have been reported. If silylation of ethylamine is attempted with trimethylsilyl chloride, only 13% of NJ -bis(trimethylsilyl)ethylamine is obtained in addition to the major product iV-(trimethylsilyl)ethylamine. However, N,N-bis(trimethylsilyl)amines can be prepared by silylation of monosi-lylamines with trimethylsilyldiethylamine in the presence of catal3Tic ammonium sulfate or ammonium chloride. Another convenient method for the preparation of Af,A-bis(tri-methylsilyl)alkylamines has recently been reported. There trimethylsilyldiethylamine has been found to be effective in the conversion of primary amines, especially aromatic systems, and their monotrimethylsilyl derivatives into the corresponding bistrimethylsilyl products in high yields. For example, when isopropyl amine (or aniline) is refluxed with 1.1 equiv of trimethylsilyldiethylamine and 1.15 equiv of methyl iodide in toluene for 4 h, bis(trimethylsilyl)isopropylamine [or bis(trimethylsilyl)aniline] can be obtained in 99% yield (or 88% yield based on GC) (eqs 16 and 17). 

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. 

Nevertheless, silyl enol ethers can be conveniently prepared by the reaction of ketones with trimethylsilyldiethylamine and methyl iodide. The process involves heating a mixture of 1.2 equiv of trimethyl silyldiethylamrne and 1.3 equiv of methyl iodide at 60 °C for 1 h, and subsequently ketone is added dropwise (eqs 22 and 23). ... 

The combination of trimethylsilyldiethylamine and methyl iodide transforms both the cyclic and the acyclic ketones into silyl enol ethers in high yield, with favored formation of the more thermodynamically stable isomer. 

Among the main commercial silylation agents, we can mention N,0-bis(tri-methylsilyl)trifluoroacetamide (BSTFA) to which is generally added 1% of trimethyl-chlorosilane (TMCS), the latter playing the role of a catalyst in the reaction, n-methyl-n-(trimethylsilyl)trifluoroacetamide (MSTFA), n-trimethylsilyldiethylamine (TMSDEA), N,0-bis(trimethylsilyl)acetamide (BSA), generally used in mixture with trimethylchlorosilane, and l-(trimethylsilyl)imidazole (TMSl). These molecules are presented in Figure 1.2. 

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