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26.6.5.1.2.2 Variation 2: Oxidation with Osmium(VIII) Oxide/4-Methylmorpholine N-Oxide

DOI: 10.1055/sos-SD-026-00761

Suffert, J., Science of Synthesis, (2005) 26, 942.

An especially mild oxidative procedure for the formation of α-hydroxy ketones from silyl enol ethers uses a catalytic amount of osmium(VIII) oxide, together with 4-methylmorpholine N-oxide monohydrate. The oxidation is carried out in aqueous acetone at −10 to 25°C and is allowed to proceed until all the enol ether has reacted. Subsequent workup affords α-hydroxy ketones in modest to excellent yields. Hydroxylation normally proceeds best at methine or methylene positions, but methyl groups can be oxidized in some circumstances; a notable example of this type of reaction is observed in the hydroxylation of the silyl enol ether ‌232‌, which gives 21-hydroxypregn-4-ene-3,20-dione (‌233‌) in 73% yield (‌Scheme 104‌).[‌195‌]

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References

[195] MeMeeeeee, M. M.; Meeeeee, M.; Meeeeee, M. M., Meeeeeeeeee Meee., (8888) 88, 888.

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  • 8.Meeeee-Meee, (8888) 8/8e, 8888.
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  • 8.Meeeee-Meee, (8888) M 88e, 8888.
  • 8.Meeeee-Meee, (8888) M 88e, 8888.

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