Trimethylchlorosilane activation

With Trimethylchlorosilane. Rather recently [60] it was found that activation of zinc with TMClSi augmented the yield of Zn-Barbier reactions with allylic halides considerably. This unexpected activation by the silane was found earlier for Reformatsky reactions with ethyl 2-bromopropanoate [61] also trimethylchlorosilane-activated lead was applied in Pb-Barbier reactions with crotyl bromide [62] and allyl bromide [63]. 

Another acylated ampicillin derivative with expanded antimicrobial spectrum is piperacil1 in (19). Its synthesis begins with 1-ethyl-2,3-diketopiperazine (j7, which itself is made from ]i-ethylethylenediamine and diethyl oxalate), which is activated by sequential reaction with trimethylchlorosilane and then trichloromethyl chioroformate to give This last... 

Byproducts, such as methyltrichlorosilane (Mj), trimethylchlorosilane (M3), methyldichlorosilane (MH), and some residuals (R) having a boiling point above 70 C are also produced. One of the most efficient ways to prepare the active copper-silicon alloy is by the uniform mixing of CuCl and silicon particles. The following reaction takes place when the mixture is heated to the reaction temperature ... 

Example 10 trimethylchlorosilane TMCS has been found an effective activator in the typical synthesis of dinucleotides in solution and its utility is comparable with that of tetrazole [34]. An example of this activation is the reaction of thymidine with tris(dimethylamino)phosphine. 

Example 33 trimethylchlorosilane (TMCS) has been found to be a highly effective activator in typical couplings leading to dinucleotides and similar biophosphates, and is comparable with tetrazole and imidazolium salts [34]. The optimal amount of this activator is below the stoichiometric ratio. 

Example 50 as shown in several examples trimethylchlorosilane (TMCS) acts as a highly efficient catalytic activator for the replacement of a P hjs[R2 amino group by alcohols to form the corresponding esters. Michalski and associates have noticed that compounds can also react as reagents for the replacement of a fluorine ligand by an appropriate alcohol when at least one equivalent of TMCS is used. This reaction is relatively slow. Its driving force is the formation of trimethylfluorosilane [83]. 

Formamidines have been recognized as good activators for the a-deprotonation of amines at the a-position.141 Trapping the anions with trimethylchlorosilane led to the corresponding SMA.142... 

In view of the limited stability of the "carbenoid" LiCsCCb Cl, functionalization reactions have to be carried out a temperatures that are as low as possible Silylations of metallated acetylenes are usually rather slow in E12O at temperatures below -20 C. A small amount of HMPT appears to cause a considerable enhancement of the rates of silvlation with trimethylchlorosilane. It is not known whether this effect is only due to the typical properties of HMPT as a dipolar aprorir solvent (also shown in alkylation with alkyl halides) or whether it is a result of active participation of this solvent in the reaction as depicted in the following equations ... 

Of the chemical methods to separate the azeotropic mixture of silicon tetrachloride and trimethylchlorosilane, etherification is the most convenient one. This method is based on the different activity of components in the reactions of partial etherification by alcohols or phenols. Silicon tetrachloride is the first to interact with alcohols or phenols, eventually forming tetraloxy- or tetraaroxysilanes ... 

Trimethylchlorosilane reacts with alcohols or phenols much more slowly, and at certain quanitities of phenol or alcohol does not participate in the reaction altogether. Methyl alcohol cannot be used to separate azeotropic mixture, because in this case there is an active secondary reaction between methyl alcohol and liberated hydrogen chloride with the formation of methylchloride and water. Water hydrolyses the reaction prod-... 

TMS production involves one specific functional group (-OH, -COOH, =NH, -NH2, or -SH), which loses an activated hydrogen and is replaced by a trimethylsilyl group (Proestos et ah, 2006). To achieve silylation, some authors have used BSTFA (N,0-hA(trimethyl-silyl)trifluoroacetamide) and TMCS (trimethylchlorosilane) successfully in several matrices (e.g. aromatic plants, cranberry fixiit) (Zuo et ah, 2002 Proestos et ah, 2006). Using silylated derivatives is advantageous for several reasons phenols and carboxylic acids are prone to silylation, these compounds can be derivatized in the same part of the process, and the minor products do not impede analysis and are well documented (Little, 1999 Stalikas, 2008). A two-step methylation procedure was used to analyze catechins and tannins in plant extracts. The first step used trimethylsilyl diazomethane (TMS-diazomethane) to pre-methylate the sample, and the second step used thermally assisted hydrolysis and methylation (THM). The pre-methylation step with TMS-diazomethane stabilized the dimer molecule m/z 540) by minimizing isomerization and reducing reactivity. (Shadkami et ah, 2009). 

Tsuji, R., Nakagawa, M., Nishida, A. An efficient synthetic approach to optically active P-carboline derivatives via Pictet-Spengler reaction promoted by trimethylchlorosilane. Tetrahedron Asymmetry 2003, 14,177-180. 

In a water-free process in dichloromethane as the solvent, trimethylchlorosilane (3 mol per mol Ceph C) is used to protect the carboxy and amino functions with trimethylsilyl groups. N,N-dimethylaniline is used to bind the released HC1. The solution is cooled down to -40 °C to -60 °C and the amide is activated by chlorinating with phosphorous pentachloride humidity has to be avoided. After hydrolysis and phase separation 7-ACA is isolated by crystallization from the aqueous phase with high quality and yield. 

By removal of the adsorption sites carried out by chemical reaction on the silanol group using reactive silyl compounds, such as trimethylchlorosilane (TMCS), dimethyldichlorosilane (DMCS), or hexamethyldisilazane (HMDS), to give inert silyl ethers. For example, the reaction of the active silanol sites with hexamethyldisilazane proceeds in the following manner -... 

The catalytic performance of highly siliceous ZSM-5 was greatly improved when methanol was co-fed with oxime. Thus it was further claimed that in the presence of methanol the neutral silanol was not the active site for producing s-caprolactam because they were methylated by methanol [56]. The beneficial effect of trimethylchlorosilane treatment was ascribed to reduction of amorphous sila-nols and to enhancement of hydrophobicity. The latter could facilitate the smooth desorption of the oxime [19]. 

Trimethylsilyl enol ether of camphor. The usual methods for preparation of trimethylsilyl enol ethers are unsatisfactory in the case of camphor. However, 3-endo-bromocamphor (1) is converted into the trimethylsilyl enol ether of camphor (2, >80% yield) hy reaction with activated zinc in ether in the presence of trimethylchlorosilane. 

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