Silyl enol ethers are generally prepared by reacting an enolizable carbonyl compound with a silyl electrophile and a base, or just reacting an enolate with a silyl electrophile. Since silyl electrophiles are hard and silicon-oxygen bonds are very strong, the oxygen (of the carbonyl compound or enolate) acts as the nucleophile to form a Si-O single bond.
The most commonly used silyl electrophile is trimethylsilyl chloride. To increase the rate of reaction, trimethylsilyl triflate may also be used in the place of trimethylsilyl chloride as a more electrophilic substrate.
When using an unsymmetrical enolizable carbonyl compound as a substrate, the choice of reaction conditions can help control whether the kinetic or thermodynamic silyl enol ether is preferentially formed. For instance, when using lithium diisopropylamide (LDA), a strong and sterically hindered base, at low temperature (e.g., -78°C), the kinetic silyl enol ether (with a less substituted double bond) preferentially forms due to sterics. When using triethylamine, a weak base, the thermodynamic silyl enol ether (with a more substituted double bond) is preferred.
Alternatively, a rather exotic way of generating silyl enol ethers is via the Brook rearrangement of appropriate substrates.