Tris silyl ester

Trialkylhalosilanes can be used to obtain mono, di and tri-silyl esters (9.284-9.286). Reactions of this type are more complex than indicated if the alkyl halides are not qnickly removed. 

Preparation of tris(trimethylsilyl) phosphite — Preparation of a silyl ester of a trivalent phosphorus acid for Michaelis-Arbuzov reaction... 

Triisopropylsilyl trifluoromethanesulfonate Methanesulfonic acid, trifluoro-, tris(1-methylethyl)silyl ester (11) (80522-42-5)... 

Like the silyl ethers, the stability of the silyl esters parallels the steric bulk of the substituents on the silicon atom. Tris(2,6-diphenylbenzyl)siiy1 esters confer extraordinary steric protection upon the carboxyl group.234 For example, the tris(2,6-diphenylbenzyl)silyl ester of 4-phenylbutanoic acid 104.1 [Scheme 6.104] does not react with butyllithium (2.5 equiv) after 5 h at -78 °C or methylmag-nesium bromide (2,5 equiv) at room temperature. Nor did it react with lithium aluminium hydride after 30 min at 0 °C l M HC1 in THF at 40 °C, or aqueous sodium hydroxide at 50 °C after 5 h. Ester 104.1 was reduced with diisobutyl-aluminium hydride in 99% yield to give the 4-phenyl-l-butanol (99%) and HF pyridine in THF (1 2) at 50 aC cleaved it back to the acid after 5 h. Unfortunately, the penalty for such unusual stability is high the tris(2 6-diphenyl-... 

Silyl esters are generally prepared from carboxylic acids and the corresponding silyl chlorides or silyl triflates in the presence of base, e.g. pyridine, TEA, imidazole, in CH2CI2, CHCI3, DMF, or A-Methyl-C)-(trimethylsilyl)acetamide or A,0-bis(tri-... 

Hernandez, D., Larson, G. L. Chemistry of a-silyl carbonyl compounds. 9. Synthesis of tri- and tetrasubstituted olefins from a-silyl esters. J. Org. Chem. 1984, 49, 4285-4287. 

Both diethyl trimethylsilyl phosphite and tris(trimethylsilyl) phosphite participate in conjugate addition reactions with a,p-unsaturated nitriles.With acrylonitrile, addition occurs readily at 120°C at the P position, with transfer of the silyl ester linkage to the a position of the nitrile, to give 2-silylated 2-cyanoethylphosphonates in 46-72% yields. Protodesilylation with a proton donor leads to the simple 2-cyanoethylphosphonates (Scheme 6.28). ... 

With tris(trimethylsilyl)phosphite, regiospecific and irreversible adduct formation with 2( H)-pyrimidinones gives 3,4-dihydro-4-phosphonic acid silyl esters (317) which furnish the phosphonic acid (318) on treatment with methanol (Scheme 53). The regiochemistry is attributed to the bulkiness of the phosphite reagent. The carbon-phosphorus bond resisted cleavage by TFA <87ACS(B)448>. 

The use of mass spectrometry as a detector in g.l.c. has the advantage that isomeric materials with the same retention times may still be distinguished, e.g. a phosphate and phosphonate. Mono-, di-, and tri-butyl phosphates may be separated by g.l.c. after conversion of the acidic components into their silyl esters. A dual flame photometric detector has been described for the simultaneous determination of phosphorus-, sulphur-, and chlorine-containing compounds. The method is based on the measurement of the... 

New routes to phosphoenolpyruvic acid (PEP) which have been explored involve the dealkylation of both phosphoric and carboxylic acid esters by trimethylsilyl halides, and are summarized in Scheme 2. The immediate precursor to the PEP is the tris(trimethylsilyl) ester (18) initial attempts to obtain this from ethyl bromopyruvate failed because the ester (16) could not be further silylated through de-ethylation. However, a synthesis of (18) from... 

An extremely interesting development is the intramolecular silyl group migration from a silyl ester of thiophene-3-carboxylic acid to position 2 of the ring (Equation (54)) <9lSL33>. The yields are moderate. 3-Thienyllithium has been converted to 3-(tri- -butylsilyl)thiophene by reaction with n-BUjSiCl <94TL3673>. 

Tris(silyl)phosphites undergo Arbusov-type reactions (9.287). In a mixed phosphite ester, the alkoxy carbon is preferentially attacked (9.288). The silyl ester products are hydrolysed to phos-phonic acids (9.289). 

Nonradical Reactions. Tris(trimethylsilyl)silane reacts with carbenium ions to form a silicenium ion. In this case, tris(tri-methylsilyl)silane is only slightly more reactive than trimethylsi-lane. The reaction of the silane with methyl diazoacetate in the presence of copper catalyst gives the a-silyl ester (eq 18). ... 

Ci ,H 5NO i 191988-38-2) see Gliquidone [ll -(la,3a,4p)l-3-methoxy-4-[[tris(l-mcthylethyl)silyl]-oxyjcyclohexanecarboxylic acid methyl ester (CijH fjO Si 128684-90-2) see Tacrolimus 6-methoxytropine... 

Trimethylsilyl esters of tris(thio)phosphonic acids 2070 are readily oxidized by DMSO in toluene at -30 °C to give the dimeric tetra(thia)diaphosphorinanes 2071 and HMDSO 7 [208] (cf. also the oxidation of silylated thiophenol via 2055 to diphenyl disulfide). The polymeric Se02 is depolymerized and activated by reaction with trimethylsilyl polyphosphate 195 to give the corresponding modified polymer... 

In an analogous reaction the catechol titanate 2136 is converted by TMSOTf 20, via 2137, to give the bis-(trimethylsilyl)ester 2138, which eliminates HMDSO 7 to regenerate 2136 [65] (Scheme 13.18). The intermediate compound 2137 apparently serves as catalyst for the reaction of l-0-trimethylsilyl-2,3,5-tri-0-benzyl-D-arabino-furanose with O-silylated alcohols to afford mainly the l-/ -arabinofuranosides. 

Several methods for the preparation of the parent compound in this system, tris(trimethylsilyl)phosphite, have been reported.114 118 The application of this and related reagents in reaction with alkyl halides has been reported and used for the preparation of a variety of phosphonic acid analogues of phospholipids.114119-124 Interestingly, alkyl chlorides appear to be more reactive with the silyl reagents than do alkyl iodides, a reversal of the normally observed trend with alkyl esters of the phosphorus acids. (The particular use of silyl phosphorus reagents for the synthesis of biologically significant compounds has... 

The ruthenium carbene catalysts 1 developed by Grubbs are distinguished by an exceptional tolerance towards polar functional groups [3]. Although generalizations are difficult and further experimental data are necessary in order to obtain a fully comprehensive picture, some trends may be deduced from the literature reports. Thus, many examples indicate that ethers, silyl ethers, acetals, esters, amides, carbamates, sulfonamides, silanes and various heterocyclic entities do not disturb. Moreover, ketones and even aldehyde functions are compatible, in contrast to reactions catalyzed by the molybdenum alkylidene complex 24 which is known to react with these groups under certain conditions [26]. Even unprotected alcohols and free carboxylic acids seem to be tolerated by 1. It should also be emphasized that the sensitivity of 1 toward the substitution pattern of alkenes outlined above usually leaves pre-existing di-, tri- and tetrasubstituted double bonds in the substrates unaffected. A nice example that illustrates many of these features is the clean dimerization of FK-506 45 to compound 46 reported by Schreiber et al. (Scheme 12) [27]. 

The Stille adduct of 2-bromothiophene and l-ethoxy-2-tributyl-n-stannylethene or 1-ethoxy-l-tri-n-butylstannylethene is a masked thienyl aldehyde or a masked ketone, respectively [77-80]. Vinylstannane 93, derived exclusively as the -isomer from hydrostannation of bis(trimethyl-silyl)propargyl amine (92), was coupled with 2-bromothiophene to form ( )-cinnamyl amine 94 upon acidic hydrolysis [81, 82], In another case, stereoisomerically pure phenyl ( )-2-tributylstannyl-2-alkenoate 95, arising from Pd-mediated hydrostannation of phenyl ( )-2-alkynoate, was joined with 2-iodothiophene to deliver the stereodefmed trisubstituted a,p-unsaturated ester 96 [83, 84],... 

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