Trimethylsilyl acetate, benzyl

Secondary alcohols such as cyclohexanol or 2-butanol also react on heating for 20-120 min at 80 °C with TCS 14 in the presence of BiCl3 to give the chloro compounds cyclohexyl chloride 784 and 2-chlorobutane in 93 and 90% yield, respectively, HCl, and HMDSO 7 [11, 12]. Benzyl alcohol is transformed likewise by Me3SiCl 14 after 120 min. at 80 °C into benzyl chloride in quantitative yield. Analogously, esters such as 2-acetoxypropane 785 are also converted by TCS 14 in 100% yield into chloro compounds such as 786 and trimethylsilyl acetate 142. The yS-lactone 787 gives rise to 788... 

Carboxylic acid esters. A mixture of acetic acid, 1.5 eqs. (trimethylsilyl)ethoxyacety-lene, and a little yellow HgO in 1,2-dichloroethane treated with benzyl alcohol and a little DMAP, and stirred at 40° for 25 min - benzyl acetate. Y 83%. This method is simple and suitable for compds. containing acid- and/or moisture-sensitive groups. The by-product, ethyl (trimethylsilyl)acetate, is volatile and easily removed. F.e. and with a little p-TsOH, also lactones and lactams (from the respective hydroxy- and amino-acids), and dipeptides, s. Y. Kita et al.. Synthesis 1989, 334-7. 

Although gas-liquid chromatography (GLC) is one of the most widely used separation techniques to date, its application in Bg vitamer analysis has been hampered by the high polarity of these compounds (151). The presence of polar groups in vitamin Bg compounds tends to keep them from being volatile enough for GLC. Nevertheless, GLC of a variety of Bg vitamer derivatives, including acetates, trimethylsilyl ethers, benzyl ethers, and isopropylidene derivatives, have been reported (151,152). GLC of the fully acetylated derivatives of vitamin Bg is suitable for the separation and quantification of the three unphosphorylated Bg vitamers (152). 

A soln. of TiCl4 in methylene chloride added at -78° under argon to a soln. of benzalacetophenone in the same solvent, stirred 15 min., a soln. of benzylketene methyl trimethylsilyl acetal in methylene chloride added dropwise, stirred 3 hrs., and quenched with aq. 5%-K-carbonate methyl 2-benzyl-3,5-diphenyl-5-oxo-pentanoate. Y 90%. F. e. s. K. Saigo, M. Osaki, and T. Mukaiyama, Chem. Lett. 1976, 163. 

Various S-nucleophiles are allylated. Allylic acetates or carbonates react with thiols or trimethylsilyl sulfide (353) to give the allylic sulfide 354[222], Allyl sulfides are prepared by Pd-catalyzed allylic rearrangement of the dithio-carbonate 355 with elimination of COS under mild conditions. The benzyl alkyl sulfide 357 can be prepared from the dithiocarbonate 356 at 65 C[223,224], The allyl aryl sufide 359 is prepared by the reaction of an allylic carbonate with the aromatic thiol 358 by use of dppb under neutral condi-tions[225]. The O-allyl phosphoro- or phosphonothionate 360 undergoes the thiono thiolo allylic rearrangement (from 0-allyl to S -allyl rearrangement) to afford 361 and 362 at 130 C[226],... 

Me3SiI, CH2CI2, 25°, 15 min, 85-95% yield.Under these cleavage conditions i,3-dithiolanes, alkyl and trimethylsilyl enol ethers, and enol acetates are stable. 1,3-Dioxolanes give complex mixtures. Alcohols, epoxides, trityl, r-butyl, and benzyl ethers and esters are reactive. Most other ethers and esters, amines, amides, ketones, olefins, acetylenes, and halides are expected to be stable. 

Methoxyethoxymethyl, 365 Enamino Derivatives, 365 4-Methyl-1,3-dioxolanyl Enol Acetate, 365 Pyrrolidinyl Enamine, 365 Benzyl Enol Ether, 366 Butylthio Enol Ether, 366 Protection of Tetronic Acids, 366 Trimethylsilyl Enol Ether, 367... 

Alkyl esters are efficiently dealkylated to trimethylsilyl esters with high concentrations of iodotrimethylsilane either in chloroform or sulfolane solutions at 25-80° or without solvent at 100-110°.Hydrolysis of the trimethylsilyl esters serves to release the carboxylic acid. Amines may be recovered from O-methyl, O-ethyl, and O-benzyl carbamates after reaction with iodotrimethylsilane in chloroform or sulfolane at 50—60° and subsequent methanolysis. The conversion of dimethyl, diethyl, and ethylene acetals and ketals to the parent aldehydes and ketones under aprotic conditions has been accomplished with this reagent. The reactions of alcohols (or the corresponding trimethylsilyl ethers) and aldehydes with iodotrimethylsilane give alkyl iodides and a-iodosilyl ethers,respectively. lodomethyl methyl ether is obtained from cleavage of dimethoxymethane with iodotrimethylsilane. 

Padwa et al. (75) found that the unsymmetrical miinchnone 137, which was generated from A-acetyl-7/-benzylglycine (136) and refluxing acetic anhydride, reacts with methyl propiolate to give an 8 1 mixture of pyrroles 138 and 139. The same product ratio is obtained from the reaction of methyl propiolate and the azomethine ylide derived from 7/-benzyl-A(-(a-cyanoethyl)-A(-[(trimethylsilyl)-methyl] amine. 

Reduction of derivatives of ally lie alcohols. Nickel boride can effect reduction of allylic alcohols to alkenes, but yields are generally improved by reduction of the acetates, benzoates, or trifluoroacetates.1 Reduction of allylic benzyl ethers to alkenes is effected in higher yield with Raney nickel. Methyl ethers are not reduced by either reagent. The trimethylsilyl ethers of allylic alcohols are reduced to alkenes by nickel boride in diglyme.2... 

Trimethylsilyl)ethyl 2,3,6-tri-0-benzyl-4-0- Acetal Toluene Benzoyl chloride ... 

The seven-membered phostone 252 was synthesized by the reaction of methyl 2,3-di-0-benzyl-4,6-0-benzyl-idene-a((3)-D-glucopyranoside 251 with triethyl phosphate and trimethylsilyl trifluoromethanesulfonate. Protecting the acetal group of 251 interacted with triethyl phosphite and opened to give 252, which can be further selectively hydrolyzed or deprotected to give 253 or 254 <2003TL8797>. 

Acetals and ethers can also be used to produce benzylic car-bocations by reacting with a Lewis acid. Treatment of acetals derived from chiral 2-substituted benzaldehyde chromium tricarbonyl complexes with trimethylsilyl triflate followed by reaction with a silyl enol ether give diastereomerically pure alkylation products (Scheme 98). Benzylic alcohols can be... 

Trimethylsilyl chloride also gives the N -product alone in simple models, but this is probably the consequence of thermodynamic control in any event N -trialkylsilyl derivatives are much too labile to be useful as stepping stones to N"-alkylhistidines. The only thoroughly studied example of exclusive mono-N -derivatization is the reaction of acetic anhydride with acylhistidine esters, when thermodynamic control appears to operate. Thus, N -(benzyl-oxycarbonyl)histidine methyl ester gives only the M-acetyl derivative, providing a third kind of intermediate which is useful for N"-alkylation with reactive halides (see Section 2.6.2.3).1 1... 

Aziridines react with nucleophiles other than carbon nucleophiles. In the presence of TBAF, trimethylsilyl azide react with V-tosylaziridines to give the azido A-tosylamine. A-Benzylic aziridines are opened by trimethylsilyl azide in the presence of a chromium catalyst. Acetic anhydride reacts with N-tosylaziridines, in the presence of PBU3, to give the A-tosylamino acetate. A-Tosylaziridines react with InCls to give the chloro A-tosylamine. ... 

Enantiomerically pure 3-oxo-8-oxabicyclo[3.2.1]octyl-2-yl derivatives were obtained by [4 -h 3] cycloaddition of furan with chiral 1,2-dioxyallyl cation engendered in situ by acid-catalyzed heterolysis of enantiomerically pure, mixed acetals derived from 1,1-dimethoxy-acetone and enantiomerically pure, secondary benzyl alcohols [203]. For instance, mixed acetal 439 is converted into the silyl enol ether 440. In the presence of a catalytic amount of trimethylsilyl triflate, 440 generates a cationic intermediate that adds to furan at - 95°C, giving... 

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