- Silyl enol ether
Silyl enol ethers in
organic chemistry are a class oforganic compound s sharing a commonfunctional group composed of anenolate bonded through itsoxygen terminus to anorganosilicon group.Silyl enol ethers are important intermediates in
organic synthesis .Organic synthesis
* Trimethylsilyl enol ethers can be prepared from ketones in presence of a strong base and
trimethylsilyl chloride .
* Silyl enol ether can form by capturing anyenolate formed in anucleophilic conjugate addition . [Organic Syntheses , Coll. Vol. 9, p.564 (1998); Vol. 73, p.123 (1996) [http://www.orgsynth.org/orgsyn/prep.asp?prep=cv9p0564 Article] ] [Organic Syntheses , Coll. Vol. 8, p.277 (1993); Vol. 66, p. 43 (1988) [http://www.orgsynth.org/orgsyn/prep.asp?prep=cv8p0277 Article] .]
* A rather exotic way to generate silyl enol ethers is via theBrook rearrangement of appropriate substrates. [ R. Tong, F. E. McDonald,Angewandte Chemie , Int. Ed. 2008, 47, 1-4.]Organic reactions
Silyl enol ethers react as
nucleophile s in:
*Mukaiyama aldol addition
*Michael reaction s
*Alkylation s
*Haloketone formation withhalogen s [Organic Syntheses , Coll. Vol. 8, p.286 (1993); Vol. 69, p.129 (1990) [http://www.orgsynth.org/orgsyn/prep.asp?prep=cv8p0286 Article] ]
*Acyloin formation byorganic oxidation withmCPBA [Organic Syntheses , Coll. Vol. 7, p.282 (1990); Vol. 64, p.118 (1986) [http://www.orgsynth.org/orgsyn/prep.asp?prep=cv7p0282 Article] .]aegusa oxidation
In the Saegusa oxidation certain silyl enol ethers are oxidized to
enone s withpalladium(II) acetate . In the original publication ["Synthesis of alpha, beta-unsaturated carbonyl compounds by palladium(II)-catalyzed dehydrosilylation of silyl enol ethers" Yoshihiko Ito, Toshikazu Hirao, and Takeo SaegusaJ. Org. Chem. ; 1978; 43(5) pp 1011 - 1013; DOI|10.1021/jo00399a052] the amount of palladium is less than stochiometric and 1,4-benzoquinone is used assacrificial catalyst . The intermediate is an oxo-allylpalladium complex.:
In one application a dienenone is synthesized in two steps from a cyclohexanone ["Formation of Benzo-Fused Carbocycles by Formal Radical Cyclization onto an Aromatic Ring" Derrick L. J. Clive and Rajesh Sunasee
Org. Lett. ; 2007; 9(14) pp 2677 - 2680; (Letter) DOI|10.1021/ol070849l] [reagents in step 1 aretrimethylsilyl triflate and2,6-lutidine ] ::
Ketene silyl acetals
Ketene silyl acetals are related compounds formally derived from
ketene s andacetal s with general structure R-C=C(OSiR3)(OR').References
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