Ketene methyl trimethylsilyl acetals

Jlfetai reduction of malonates. Dimethyl dimethyltnalonate (I) is reduced by sodium dispersed in xylene containing trimethylchlorosilane (TMCS) to dimethyl-ketene methyl trimethylsilyl acetal (2) ... 

Few ketene acetals with electron-accepting substituents are known. Ainsworth et al. (43,44) have described a number of methyl trimethylsilyl acetals (25,... 

Okamoto, Y, Azuhata, T., and Sakurai, H.. Dialkyl 3-alkoxy-3-(tiimethylsiloxy)-2-propenephospho-nate. A one step preparation of (dialkoxyphosphinyl)methyl-substituted ketene alkyl trimethylsilyl acetal, Chem. Lett., 1265, 1981. 

A new and efficient combination for silylation is trimethylsilyl chloride-lithium sulphide. Even hindered hydroxy-groups are silylated at room temperature in neutral conditions, although the mechanism of the process is not yet clear. 4-Dimethylaminopyridine (DMAP) has been shown to be an efficient catalyst for the silylation of alcohols by t-butyldimethylsilyl chloride and to be more selective than the imidazole traditionally used. Two new methods for removal of the t-butyldimethylsilyl group are treatment with boron trifluoride etherate and reaction with aqueous HF in acetonitrile. The O-silyl derivatives of normal carboxylic esters, i.e. keten methyl trialkylsilyl acetals (59), have been investigated in silyl transfer to alcohols (Scheme 31) they have the advantage of... 

Related Reagents. Ethyl Diethoxyacetate Glyoxylic Acid Diethyl Dithioacetal Ketene Bis(trimethylsilyl) Acetal Ketene Diethyl Acetal l-Methoxy-2-trimethylsilyl-l-(trimethylsilyl-oxyjethylene Methyl Glyoxylate 8-Phenyhnenthyl Glyoxylate Tetramethoxyethylene Tris(trimethylsilyloxy)ethylene. 

The mechanisms for nucleophilic GTP and electrophilic GTP are not the same. Electrophilic GTP proceeds by an associative or concerted mechanism that does not involve anionic propagating centers. Initiation involves a concerted addition of methyl trimethylsilyl dimethyl ketene acetal to monomer to form species XXV. The overall effect is to transfer... 

MICHAEL ADDITIONS Alumina. Aluminum chloride. Cesium fluoride-Silicon(lV) cthoxidc. 1,4-Diazabicyclo[2.2.2]octanc. l,8-Diazabicyclo[5.4.0]-7-undecene. Ketene r-butyldimethylsilyl methyl acetal. Lithium acetylides. (S)-( + )-2-Mcthoxymethylpyrrolidine. Methyl lithiodithioacetate. Methyl (phcnylsulfinyl)acetate. Methyl 2-trimcthylsilylacrylate. Nickel carbonyl. Organocopper reagents. 8-Phenylmcnthol. Phenyl 2-(trimethylsilyl)ethynyl sulfone. Tetra-n-butylammonium fluoride. Tiianium(IV) chloride. 3-Triisopropylsilylpropynyllithiuni. Zirconium(IV) n-propoxiilc... 

In contrast to the carbene and carbenoid chemistry of simple diazoacetic esters, that of a-silyl-a-diazoacetic esters has not yet been developed systematically [1]. Irradiation of ethyl diazo(trimethylsilyl)acetate in an alcohol affords products derived from 0-H insertion of the carbene intermediate, Wolff rearrangement, and carbene- silene rearrangement [2]. In contrast, photolysis of ethyl diazo(pentamethyldisilanyl)acetate in an inert solvent yields exclusively a ketene derived from a carbene->silene->ketene rearrangement [3], Photochemically generated ethoxycarbonyltrimethyl-silylcarbene cyclopropanates alkenes and undergoes insertion into aliphatic C-H bonds [4]. Copper-catalyzed and photochemically induced cyclopropenation of an alkyne with methyl diazo(trimethylsilyl)acetate has also been reported [5]. 

Mixed ketene 0,5-acetal derivatives (157) can be readily prepared from the reaction of [methoxy(phe-nylthio)(trimethylsilyl)methyl]lithium, generated from the mixed acetal (158), with aldehydes and ketones (Scheme 70). 

Dimethyl monothiomaleate (56) and monothiofumarate (57) are formed in a complicated reaction from 2,5-dimethoxythiophene via an intermediate of the orthoester type. 0-Trimethylsilyl ketene-0,0-acetals are readily formed from carboxylic esters and can be transformed to thioxoesters, without being isolated, by reaction with hydrogen sulflde, according to equation (34). Methyl thioxoarachido-nate (58) was prepared by this route. ... 

In the presence of catalytic amounts of 1, methyl trimethylsilyl ketene acetals are oxidized with urea hydrogen peroxide to afford a-hydroxy and a-siloxy esters [3, 21b]. 

Functionalized initiators. Their use leads to terminal functionalized polymers. Thus, with phosphorus-containing ketene silyl acetals, trimethylsilyl methyl sulfide, trimethylsilyl cyanide, dimethylketene-bis(trimethylsilyl)acetal, or dimethylketene-2-(trimethylsiloxy) ethyltrimethyl silyl acetal, terminal phosphoric acid groups, thiomethyl groups, and cyanide, hydroxy, or carboxyl groups are readily introduced [234]. Furthermore, the styrene end group can also be achieved [247]. 

Related Reagents. f-Butyl a-Lithiobis(trimethylsilyl)acetate f-Butyl Trimethylsilylacetate Ethyl Bromozincacetate Ethyl Lithioacetate Ethyl Trimethylsilylacetate Ketene Bis(trimethyl-silyl) Acetal Ketene f-Butyldimethylsilyl Methyl Acetal l-Methoxy-2-trimethylsilyl-l-(trimethylsilyloxy)ethylene Methyl (Methyldiphenylsilyl)acetate Methyl 2-Trimethylsilyl-acrylate Triethyl Phosphonoacetate Trimethylsilylacetic Acid. 

Related Reagents. Methoxy(phenylthio)(trimethylsilyl)-methane (7) is prepared by metalation-silylation of phenyl-thiomethyl methyl ether.[Methoxy(phenylthio)(trimethylsilyl)-methyl]lithium (8), prepared from (7) by metalation with s-butyllithium in the presence of TMEDA, undergoes clean and efficient Peterson alkenation with aldehydes to give ( )-ketene-0,5-acetals stereoselectively, which can then be hydrolyzed to thioesters (eq 10). ... 

It is thought that the acid lowers the basicity of the solution increasing catalyst lifetime. The addition of acid alone resulted in total hydrolysis of the sUyl-enol ether. Methyl trimethylsilyl ketene acetals undergo oxidation using the anhydrous MTO/UHP... 

Considerable efforts have been devoted to the stereoselective introduction of a /(-methyl function in intermediates for the synthesis of 1 jS-methylcarbapenems. While the trimethylsilyl trifluoromethanesulfonate catalyzed reaction of a 4-acetoxyazetidinone derivative with ketene acetals shows no selectivity, ketene thioacetals lead to stereoselective formation of the a-methyl isomer108. The zirconium enolate, however, shows high /(-methyl selectivity. 

Tocopheryl)propionic acid (50) is one of the rare examples that the o-QM 3 is involved in a direct synthesis rather than as a nonintentionally used intermediate or byproduct. ZnCl2-catalyzed, inverse hetero-Diels-Alder reaction between ortho-qui-none methide 3 and an excess of <2-methyl-C,<9-bis-(trimethylsilyl)ketene acetal provided the acid in fair yields (Fig. 6.37).67 The o-QM 3 was prepared in situ by thermal degradation of 5a-bromo-a-tocopherol (46). The primary cyclization product, an ortho-ester derivative, was not isolated, but immediately hydrolyzed to methyl 3-(5-tocopheryl)-2-trimethylsilyl-propionate, subsequently desilylated, and finally hydrolyzed into 50. 

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