Amines silylation

Thus removal of water from classical rather inactive fluoride reagents such as tetrabutylammonium fluoride di- or trihydrate by silylation, e.g. in THF, is a prerequisite to the generation of such reactive benzyl, allyl, or trimethylsilyl anions. The complete or partial dehydration of tetrabutylammonium fluoride di- or trihydrate is especially simple in silylation-amination, silylation-cyanation, or analogous reactions in the presence of HMDS 2 or trimethylsilyl cyanide 18, which effect the simultaneous dehydration and activation of the employed hydrated fluoride reagent (cf, also, discussion of the dehydration of such fluoride salts in Section 13.1). For discussion and preparative applications of these and other anhydrous fluoride reagents, for example tetrabutylammonium triphenyldifluorosilicate or Zn(Bp4)2, see Section 12.4. Finally, the volatile trimethylsilyl fluoride 71 (b.p. 17 °C) will react with nucleophiles such as aqueous alkali to give trimethylsilanol 4, HMDSO 7, and alkali fluoride or with alkaline methanol to afford methoxytri-methylsilane 13 a and alkali fluoride. 

HMDS alone is seldom used for the silylation of amines and addition of a catalyst is usually necessary [86]. Particularly with polyfunctional amines, silylation does not proceed quantitatively and non-uniform products are obtained. 

Over the last decade, a considerable number of reactions has been studied (11,35) (i) olefins oxidation (38,39), hydroboration, and halogenation (40) (ii) amines silylation (41,42), amidation (43), and imine formation (44) (iii) hydroxyl groups reaction with anhydrides (45), isocyanates (46), epichloro-hydrin and chlorosilanes (47) (iv) carboxylic acids formation of acid chlorides (48), mixed anhydrides (49) and activated esters (50) (v) carboxylic esters reduction and hydrolysis (51) (vi) aldehydes imine formation (52) (vii) epoxides reactions with amines (55), glycols (54) and carboxyl-terminated polymers (55). A list of all the major classes of reactions on SAMs plus relevant examples are discussed comprehensively elsewhere (//). The following sections will provide a more detailed look at reactions with some of the common functional SAMs, i.e hydroxyl and carboxyl terminated SAMs. 

Figure 9.2 Using different chemical functionalities, pSi surfaces can be tailored to selectively adsorb and efficiently ionize analytes. Left to right DIOS-MS spectra of 500fmol of BSA digest analyzed on 8-month-old TMS-derivatized DIOS chip, carbohydrate mix containing sucrose (MNa 365) and maltotriose (M Na 527) on amine-silylated pSi surface, and small-mole-...

Trialkylsilyl enol ethers have also been aminated by (1), providing access to a-amino ketone derivatives (eq 5). The products of the amination have the NHTs group in an axial orientation due to interactions between the ji orbital and the a orbital of the C-N bond. Compound (1) was used to aminate silyl enol ether (7) in the synthesis of the benzomorphanone core stmcture (8) (eq 6). ... 

Electrophilic Silylation Reagent. l,2-Bis(chlorodimethyl-silyl)ethane is not only an effective amine silylating reagent, but can also be employed in reactions with other anions. For example, when treated with the silver sulfonate salt as in eq 11, the nonafluorobutanesulfonic acid silyl ester (27), an extremely powerful silylating reagent, results.Carbanions are also effectively trapped by (1) A series of rigid butadiene Diels-Alder precursors such as (28) have been prepared in this fashion as outlined in eq 12.12... 

The oxidation of higher alkenes in organic solvents proceeds under almost neutral conditions, and hence many functional groups such as ester or lac-tone[26,56-59], sulfonate[60], aldehyde[61-63], acetal[60], MOM ether[64], car-bobenzoxy[65], /-allylic alcohol[66], bromide[67,68], tertiary amine[69], and phenylselenide[70] can be tolerated. Partial hydrolysis of THP ether[71] and silyl ethers under certain conditions was reported. Alcohols are oxidized with Pd(II)[72-74] but the oxidation is slower than the oxidation of terminal alkenes and gives no problem when alcohols are used as solvents[75,76]. 

Silylation of alcohols, amines and carboxylic acids with hydrosilanes is catalyzed by Pd catalysts[l 19], Based on this reaction, silyl protection of alcohols, amines, and carboxylic acids can be carried out with /-butyldimethylsilane using Pd on carbon as a catalyst. This method is simpler and more convenient than the silylation with /-butyldimethylsilyl chloride, which is used commonly for the protection. Protection of P-hydroxymethyl-(3-lactam (125) is an example 120]. 

Fig. 37. Resist images obtained with a cross-linking monocomponent TSI resist (PHOST polymer), cross-linked by photo-oxidation using light at 193-nm wavelength. After exposure, the film was treated with a vapor of dimethyl silyl dimethyl amine and then plasma developed using O2—RIE (122).

Synthesis of Silicone Monomers and Intermediates. Another important reaction for the formation of Si—C bonds, in addition to the direct process and the Grignard reaction, is hydrosdylation (eq. 3), which is used for the formation of monomers for producing a wide range of organomodified sihcones and for cross-linking sihcone polymers (8,52—58). Formation of ether and ester bonds at sihcon is important for the manufacture of curable sihcone materials. Alcoholysis of the Si—Cl bond (eq. 4) is a method for forming silyl ethers. HCl removal is typically accomphshed by the addition of tertiary amines or by using NaOR in place of R OH to form NaCl. 

V-trimethyl silyl diethyl-amine [996-50-9] TMSDEA (CH3)3SiNH(C3H3)3... 

V-Trimethyl silyl diethyl amine (TMSDEA) is a stroagly basic silylatiag reageat and is particulady usehil for derivatiziag low molecular weight acids. The reaction by-product, diethylamine, is volatile enough to be easily removed from the reaction medium. 

Early attempts to produce cephalosporin analogs by varying the 7-acylamino substituent were frustrated because, in contrast to previous experience with penicillins, a good method for producing the necessary 7-amino compound (33a) could not be found. This problem was finally solved when it was discovered that diazotization of the a-aminoadipyl residue produces an iminolactone (33b) which can be hydrolyzed to the free amine in good yield. Subsequently an improved procedure was developed which involves silylation of the carboxyl groups followed by reaction with phosphorus pentachloride to yield iminochloride (33c)... 

Me3Si)2NH, Me3SiCl, Pyr, 20°, 5 min, 100% yield. ROH is a carbohydrate. Hexamethyldisilazane (HMDS) is one of the most common sily-lating agents and readily silylates alcohols, acids, amines, thiols, phenols, hydroxamic acids, amides, thioamides, sulfonamides, phosphoric amides, phosphites, hydrazines, and enolizable ketones. It works best in the presence of a catalyst such as X-NH-Y, where at least one of the group X or Y is electron-withdrawing. ... 

Me3SiSEt. Alcohols, thiols, amines and carboxylic acids are silylated. 

Trimethylsilyl cyanide. This reagent readily silylates alcohols, phenols, and carboxylic acids, and more slowly, thiols and amines. Amides and related compounds do not react with this reagent. The reagent has the advantage that a volatile gas (HCN is highly toxic) is the only byproduct. 

Trimethylsilylimidazole, CCI4 or THF, rt. This is a powerful silylating agent for hydroxyl groups. Basic amines are not silylated with this reagent, but as the acidity increases silylation can occur. 

Et3SiCl, Pyr. Triethylsilyl chloride is by far the most common reagent for the introduction of the TES group. Silylation also occurs with imidazole and DMF arid with dimethylaminopyridine as a catalyst. Phenols, carboxylic acids, and amines have also been silylated with TESCl. 

TBDMSCl, imidazole, DMF, 25°, 10 h, high yields. This is the most common method for the introduction of the TBDMS group on alcohols with low steric demand. The method works best when the reactions are mn in very concentrated solutions. This combination of reagents also silylates phenols, hydroperoxides, and hydroxyl amines. Thiols, amines, and carboxylic acids are not effectively silylated under these conditions. ... 

A-/-Butyldimethylsilyl-7V-methyltrifluoroacetamide, CH3CN, 5 min, 97-100% yield.This reagent also silylates thiols, amines, amides, carboxylic acids, and enolizable carbonyl groups. 

Thionyl imide, HNSO, is a thermally unstable gas, which polymerizes readily. It can be prepared by the reaction of thionyl chloride with ammonia in the gas phase. Organic derivatives RNSO have higher thermal stability, especially when R = Ar. The typical synthesis involves the reaction of a primary amine or, preferably, a silylated amine with thionyl chloride. A recent example is the preparation of FcNSO (Fc = ferrocenyl) shown in Eq. 9.8. In common with other thionylimines, FcNSO readily undergoes SO2 elimination in the presence of a base, e.g., KO Bu, to give the corresponding sulfur diimide FcNSNFc. 

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