Trimethylsilane, derivatives

However, the reaction rate is also increased by using silanes with R groups such as fluoro or alkoxy instead of alkyl. In fact, there are only a few successful examples of coupling reactions using trimethylsilane derivatives. 

Among the derivates of HBAs, further compounds have been identified. GUntert et al. (1986) identified ethyl esters of vanillic acid and p-hydroxybenzoic acid, and methyl esters of vanillic acid and protocatechuic acid. Ethyl esters of protocatechuic acid and vanillic acid, as well as the glucose ester of vanillic acid, were isolated from a German Riesling wine (Baderschneider and Winterhalter 2001). Analytically, HBA are mostly determined as trimethylsilane derivatives by using... 

Taking into account the sensitivity of Si-X bonds to hydrolysis and the Si-X bond energies of the applied trimethylsilane derivatives we propose the mechanism given in Fig. 3 as a combination of the literature models. 

PSLs prepared via electrochemical etching of Si wafers in dilute hydrofluoric acid can be easily modified with trimethylsilane derivatives MesSiX. The silylation of PSLs with functionalized silanes, however, leads in almost every case to a loss of functionality. Only for 2-chloroethyltriethoxysilane and benzyltriethoxysilane can the functional groups be preserved. Future studies, therefore, will concentrate on the anchoring process and on the characterization of the uppermost layers of modified PSL samples with TOF-SIMS and XPS. 

Some polar species can be difficult to chromatograph, but such compounds may often be chemically derivatized to enhance the separation and detection of eluted analytes. Derivatization is a chemical reaction with an added reagent to produce specific products clearly derived from the reactants, but with improved GC-MS analytic properties. Thus, TMS (trimethylsilane) derivatives of alcohols are synthesized with his(trimethylsilyl) trifluoroacetamide, primary and secondary amines are reacted with acylation reagents, and many other analogous reactions are likewise possible. Derivatives may also be implemented in conjunction with SPME, and derivatization reactions can be performed on-fiber. 

Fig. 5. Synthesis of goldinamine derivatives and aurodox when is trimethylsilane.

For low molecular weight aliphatic acids, try TMSDEA reagent. Otherwise, use MSTFA, BSTFA, or TRI-SIL BSA (Formula P). For analysis of the keto acids, methoxime derivatives should be prepared first, followed by the preparation of the trimethylsilane (TMS) derivatives using BSTFA reagent. This results in the meth-oxime-TMS derivatives. 

Treatment of a-sulfonyl carbanion with (iodomethyl)trimethylsilane gave / -trimethylsilyl sulfones " . Alkylation of jJ-trimethylsilyl sulfones 235 gave various -trimethylsilyl sulfones . The use of (iodomethyl)tributylstannane instead of (iodomethyl)trimethylsilane was shown to afford a tributylstannanyl derivative . This compound has been used for syntheses of terminal olefins " . 

The compounds benzonitrile, p-methylbenzonitrile, /)-methoxybenzonitrile, p-trifluoromethyl-benzonitrile, /)-methoxycarbonylbenzonitrile, and triethoxysilane are commercial products and are degassed and stored under argon before use. Trimethylsilane was prepared according to a literature report [38]. The nitrile (9.8 mmol) and the hydrosilane (49 mmol) are added to the rhodium catalyst (0.1 mmol) contained in a Carius tube. When using trimethylsilane, the operation is performed at —20°C. The tube is closed and the mixture stirred at 100 °C for 15h. The liquid is separated by filtration and the excess of hydrosilane removed under vacuum to leave the N, Wdisilylamine derivative. If necessary, a bulb to bulb distillation is performed to obtain a completely colorless liquid. The yields obtained in the different runs are reported in Table 6. The product have been characterized by elemental analysis, NMR spectroscopy, and GC-MS analysis. 

Analogous reactions were also used for the preparation of silyl derivatives, through reaction with (chloromethyl)trimethylsilane ... 

Repeated TLC of active, pooled fractions from Red Flame grapes revealed major spots with Ry s corresponding to those of catechin and epi-catechin, identical color reaction with p-toluenesolfonic acid spray reagent, and coelution of trimethylsilane (TMS) derivatives by GC with reference samples of these flavans. However catechin and epicatechin were assayed with the bacterial strains described and no activity was detected. TMS-derivatized samples of active grape flavans were examined by GC-MS, but a search for the molecular ions of a number of known wr-inducing phenolics yielded negative results. 

PVC, polyamides, unsaturated crosslinked polyesters, ABS, and wood . Di- and tri-benzotriazole photostabilizers, such as (874) and (875) are synthesized from 2-nitro-benzenediazonium salts and an excess of 1,3-dihydroxybenzene or 1,3,5-trihydroxybenzene <85Mi 40i-0l>. The dibenzotriazole derivatives (874b and 875b) can be used as polymerizable acrylic UV absorbers <84PB237>. A few or/Ao-urethane and -trimethylsilane substituted 2-phenylbenzotriazoles (876 and 877) show similar photostabilization activity . Weather resistance of low-density polyethylene is improved by the addition of a benzotriazole-type photostabilizer <90M140i-04>. 

The present method offers a more efficient and convenient two-step route to the parent a,B-unsaturated acylsilane derivative. The first step in the procedure involves the conversion of allyl alcohol to allyl trimethylsilyl ether, followed by metalation (in the same flask) with tert-butyllithiura at -75°C. Protonation of the resulting mixture of interconverting lithium derivatives (2 and 3) with aqueous ammonium chloride solution furnishes (1-hydroxy-2-propenyl)trimethylsilane (4), which is smoothly transformed to (1-oxo-2-propenyl)trimethylsilane by Swern oxidation. The acylsilane is obtained in 53-68% overall yield from allyl alcohol in this fashion. 

Trialkylaryltin derivatives 30 are converted into fluoro-substituted derivatives 31. 37-38 (4-Mcth-oxyphenyl)trimethylsilane (32) in acetonitrile gives 4-fluoroanisole and (3-fluoro-4-meth-oxyphenyl)trimethylsilane in the ratio 1 2. A -Methyldiethanol esters of arylboronic acids 33 (l-aryl-5-methyl-2,8-dioxa-5-azonia-l-boranuidabicyclo[3.3.0]octanes) are converted into tluoroaromatic compounds with cesium fluoroxysulfate in acetonitrile in the presence of 1,3-dinitrobenzene at room temperature.39-40 Regiospecific synthesis of 2-fluoro-3-0-methyles-trone in 27 % yield occurs upon fluorination of the corresponding arylboronic acid with cesium fluoroxysulfate.41... 

The nucleophilic addition of a trifluoromethyl anion or its equivalent to an activated carboxylic acid derivative is another potential method for the synthesis of trifluoromethyl ketones (Scheme 8). Due to the well-known instability of the trifluoromethyl anion, the organometallic approach (Section 15.1.4.3.3) is often difficult to utilize. However, a trifluoromethyl anion equivalent, (trifluoromethyl)trimethylsilane (CF3TMS), was developed in 1984 by Ruppert and co-workers.[30] This reagent, known as Ruppert s reagent, is stable and does not undergo fluoride elimination like other equivalent trifluoromethyl anions. An obvious limitation to this method is that it is only useful for the synthesis of a-amino trifluoromethyl ketones unless other fluoroalkyl analogues of Ruppert s reagent are developed. 

A related process involves fluoride-induced desilylation in HMPA at room temperature of benzyldi-methyl(trimethylsilylmethyl)ammonium halides (20) to (21 62-84% yields R = H, 2-Me, 4-Me, 2-C1,4-Cl, 4-OAc X = Cl, Br).9 100 Compunds (20) were prepared by reaction of the corresponding benzyl halide derivatives with (dimethylaminomethyl)trimethylsilane, Me3SiCH2NMe2. The product of Stevens rearrangement (22) formed competitively and predominantly from precursors (20) having strong electron-withdrawing substituents (R = 2-COMe, 2-CN, 4-CN, 2-NO2, and 4-NO2).100... 

This behaviour was observed with testosteroxy-trimethylsilane (lb) in biological experiments33. The androgenic and myotropic activities of testosterone (la) and its silyl derivative lb were estimated by a routine assay (21-day-old castrated male rats s.c. injection once a day for 7 days autopsies the day after the last injection). The silyl compound lb was more active than testosterone itself. This observation may reflect rapid transport of the silicon compound across the lipid barrier and rapid cleavage to testosterone. 

Carbonyl Addition Diethylzinc has been added to benzaldehyde at room temperature in the presence of an ephedra-derived chiral quat (8) to give optically active secondary alcohols, a case in which the chiral catalyst affords a much higher enantioselectivity in the solid state than in solution (47 to 48, Scheme 10.6) [30]. Asymmetric trifluoromethylation of aldehydes and ketones (49 to 50, Scheme 10.6 [31]) is accomplished with trifluoromethyl-trimethylsilane, catalyzed by a quaternary ammonium fluoride (3d). Catalyst 3d was first used by the Shioiri group for catalytic asymmetric aldol reactions from silyl enol ethers 51 or 54 (Scheme 10.6) [32]. Various other 1,2-carbonyl additions [33] and aldol reactions [34] have been reported. 

V,7V-Diethylcarbamoyl trimethylsilane has been prepared by the reaction of bis(trimethylsilyl) sulphide with bis(A,A-diethylcarbamoyl) mercury (Scheme 30)16. Silylation of the carbamoyl cuprate reagent derived from a lithium amide, by addition of copper(I) cyanide and subsequent exposure to carbon monoxide (1 atm), is also effective75,110. Poor to moderate yields of carbamoyl silanes may be isolated by treatment of lithium silylamides with carbon monoxide and methyl iodide, in a reaction sequence involving a nitrogen to carbon silyl shift in an intramolecular silylation (Scheme 31)111. 

In an interesting transformation, reaction of benzoyl trimethylsilane with lithium enolates derived from various methyl ketones gives rise to 1,2-cyclopropanediols, predominantly with the cis configuration, in good yields (Scheme 77). The reaction, which proceeds through addition, Brook rearrangement and cyclization, is also successful with a,/l-unsaturated acyl silanes vide infra, Section IV.D)187. 

---