T-Butyldimethylsilyl ketene acetal

Conversion of allyl alcohol esters into their corresponding trimethylsilyl or t-butyldimethylsilyl ketene acetals, followed by mild thermolysis, results in... 

Benzylamino-2-(trimethylsilylmethyl)-but-l-ene cyclizes in the presence of acid to afford the azepine (138) <86TL5067>, and 7V-benzyl-6-(phenylsulfinyl)-hexanamide reacts with O-methyl-O-t-butyldimethylsilyl ketene acetal to afford the lactam (139) <90CPB1473>. Direct irradiation of ortho-(A -methylaminoethyl)stilbene in acetonitrile affords Af-methyl-2-phenyl-2,3,4,5-tetrahydro-benz[primary product but which undergoes demethylation upon further irradiation <92TL4249>. The demethylated product may also be obtained by irradiation of o-(3-amino-n-propyl)stilbene in the presence of w-dicyanobenzene as electron transfer agent. 

SILYLATION Bis(trimethylsilyl)urea. t-Butyldimethylchlorosilane. t-Butyldimethylsilyl trifluoromethanesulfonate. Chlorotrimethylsilane. Dimethyl(2,4,6-tri-f-butylphenoxy)chlorosilane. Ethyl trimethylsilylacctate. Ketene t-butyldimethylsilyl methyl acetal. N-Methyl-N-(/-... 

Related Reagents. For comparison and more details, see also those entries that deal with other silyl ketene acetals, in particular 1-f-butylthio-l-f-butyldimethylsilyloxypropene, ketene t-butyldimethylsilyl methyl acetal, and analogs. 

Related Reagents. t-Butyl a-Lithiobis(lrimethylsilyl)acetate t-Butyl Trimethylsilylacetate Dilithioacetate Ethyl Bromozin-cacetate Ethyl Lithioacetate Ethyl Lithio(trimethylsilyl)acetate Ketene Bis(trimethylsilyl) Acetal Ketene t-Butyldimethylsilyl Methyl Acetal l-Methoxy-2-trimethylsilyl-l-(trimethylsilyloxy)-ethylene Methyl (Methyldiphenylsilyl)acetate Trimethylsilyl-acetic Acid. 

Iodomethyltrimethylsilane, 315 Iodotrimethylsilane, 329 Ketene alkyl trialkylsilyl acetals or ke-tals, 19, 237, 306, 307, 351 Ketene f-butyl t-butyldimethylsilyl acetal, 237... 

This sultam can also be used to obtain enantiomerically pure (2R,2S)-anti-aldols 19). Thus reaction of 2 with t-butyldimethylsilyl triflate (TBDMSOTf) and N(C2H5)3 provides the (Z)-O-silyl-N,0-ketene acetal 7, which reacts with aldehydes in the... 

In the rearrangement of allyl fluoroacetates, trialkylsilyl triflates have been introduced as a new reagent for the Z-selective generation of silyl ketene acetals485. Thus, when (T)-crotyl fluoroacetates are treated at ambient temperatures with a trialkylsilyl triflate in the presence of a tertiary amine, rearranged products with a svn relationship are preferentially obtained. The ketene acetal intermediates cannot be isolated and the geometry has been deduced from the stereochemistry of the products. The selectivity of this process improves in the order triisopropyl > ferf-butyldimethylsilyl > rerf-hexyldimethylsilyl > trimethylsilyl a triethylsilyl (see Table 11). 

Ketene silyl acetals. The enolsilylation of esters is highly dependent on the bases used. Contrasting stereoselectivities in the silylation of methyl a-f-butyldi-methylsiloxyacetate are found with respect to the reaction conditions The ( )-isomer is obtained in the trimethylsilylation promoted by lithium tetramethylpiperidide, and the (Z)-isomer from the reaction with t-butyldimethylsilyl chloride in the presence of LHMDS and HMPA. 

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. t-Butyl a-Lithioisohutyrate Dilithio-acetate Ethyl Lithioacetate Ketene Bis(trunethylsilyl) Acetal Ketene f-Butyldimethylsilyl Methyl Acetal l-Methoxy-l-(tri-methylsilyloxy)propene l-Methoxy-2-trunethylsilyl-l-(tri-methylsilyloxy)ethylene Tris(trimethylsilyloxy)ethylene. 

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