SILYL ENOL ETHER

'Silyl enol ethers' in organic chemistry are a class of organic compounds sharing a common functional group comprised of an enolate bonded through its oxygen terminus to an organosilicon group.
Silyl enol ethers are important intermediates in organic synthesis.

Contents

Organic synthesis

Organic reactions

Saegusa oxidation

References

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 any enolate formed in a nucleophilic conjugate addition.^[1][2]

Organic reactions

Silyl enol ethers react as nucleophiles in:

★ Aldol reactions

★ Michael reactions

★ Alkylations

★ Haloketone formation with halogens^[3]

★ Acyloin formation by organic oxidation with mCPBA^[4]

Saegusa oxidation

In the 'Saegusa oxidation' certain silyl enol ethers are oxidized to enones with palladium(II) acetate. In the original publication ^[5] the amount of palladium is less than stochiometric and 1,4-benzoquinone is used as sacrificial catalyst. The intermediate is an oxo-allylpalladium complex.
:
In one application an dienenone is synthesized in two steps from a cyclohexanone ^{[6] [7]}:
:

References

1. Organic Syntheses, Coll. Vol. 9, p.564 (1998); Vol. 73, p.123 (1996) Article
2. Organic Syntheses, Coll. Vol. 8, p.277 (1993); Vol. 66, p. 43 (1988) Article.
3. Organic Syntheses, Coll. Vol. 8, p.286 (1993); Vol. 69, p.129 (1990) Article
4. Organic Syntheses, Coll. Vol. 7, p.282 (1990); Vol. 64, p.118 (1986) Article.

5. ''Synthesis of alpha,beta-unsaturated carbonyl compounds by palladium(II)-catalyzed dehydrosilylation of silyl enol ethers'' Yoshihiko Ito, Toshikazu Hirao, and Takeo Saegusa J. Org. Chem.; '1978'; 43(5) pp 1011 - 1013;
6. ''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)
7. reagents in step 1 are trimethylsilyl triflate and 2,6-lutidine