Enolsilyl ethers

The use of the enolsilyl ether of 1-menthone [16, 19, 21-23] and of some free triflic acid favors the formation of the thermodynamically controlled products as with free 2,2 -dihydroxydiphenyl [22] and only subsequently added HMDS 2 [22]. On reacting silylated alcohols and carbonyl compounds with pure trimethylsilyl triflate 20 under strictly anhydrous conditions no conversion to acetals is observed [24]. Apparently, only addition of minor amounts of humidity to hydrolyze TMSOTf 20 to the much stronger free triflic acid and hexamethyldisiloxane 7 or addition of traces of free triflic acid [18-21, 24, 26] or HCIO4 [25] leads to formation of acetals. 

Reactions of Nitrones and Aliphatic N-Oxides with Trimethylsilyl Cyanide, Aiiyitrimethyisiiane, Enolsilyl Ethers, and other Nucleophiles... 

Good results have been achieved in the isomerization of meso-ene-dialkyl ethers and their O-silylated derivatives [12]. The allyl silyl ether 32 reacts in the presence of a Rh-BINAP catalyst to give the chiral enolsilyl ether 33 (Scheme 10). On treatment with fluoride, cyclic ketones 34 result in excellent yield and enantioselecti-... 

SUyl enol ethers. The application of the MejSiNEtj-Mel combination in refluxing benzene for enolsilylation of ketones is demonstrated (6 examples, 85-93%). 

Enolsilylation. a-Bromo ketones and esters are transformed into trichlorosilyl enol ethers by HSiCls and EtsN (catalytic Ph3PO), which condense with ArCHO. The overall process is superior to the Wittig reaction. 

Silyl enol ethers. Kinetic enolsilylation of ketones with McjSiCl is observed by using this base and EtjN, HMPA in ether at -78°. 

Enolsilylation Magnesium hexamethyldisilazide, which is prepared electro-chemically with a Mg anode, deprotonates ketones. An ensuing silylation delivers the silyl enol ethers. 

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