0 Hits

  • Previous / Next

You are using Science Of Synthesis as a Guest.
Please login to access the full content or check if you have access via Variation 2: Oxidation with Osmium(VIII) Oxide/4-Methylmorpholine N-Oxide

DOI: 10.1055/sos-SD-026-00761

Suffert, J.Science of Synthesis, (200526942.

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]

Meeeee 888 Meeeeeeee ee e Meeee Meee Meeee eeee Meeeee(MMMM) Meeee eee 8-Meeeeeeeeeeeeeee M-Meeee[‌888‌]

Meeeeeeeeeee Meeeeeeee

88-Meeeeeeeeeee-8-eee-8,88-eeeee (888); Meeeeee Meeeeeeee:[‌888‌]

MMMMMMM: Meeeeeee ee eeeeee(MMMM) eeeee eee eeeeee ee eeeee eeeeeeeeeeeeee, eee eeeeeeeeee eeee eeeeeee eeee eeeeeeeee.

Mee eeeeeeeeeeeeee eeee eeeee 888 (888ee, 8.8eeee) ee eeeeeee (8eM) eee eeeee ee 8°M ee MeM8 (8.88eeee) ee e-MeMM (8.88eM), MMMM8M (888ee, 8.8eeee), M8M (8eM), eee eeeeeee (8eM). Mee eeeeeee eee eeeeeee ee 8°M eee 8e, eeee eeeeeee ee eeee ee 88°M, eee eeeeeee eee ee eeeeeeeeee 8e. MeMMM8 (8.88e) eee Meeeeeee (8.88e) eeee eeeee, eee eeeeeeeeee eee eeeeeee, eee eeee eeeeeeee ee eeeeee eeeeee-eeeeeeeeee eeeeeeee. Mee eeeeeeee eee eeeeeeeeeee ee eM 8 eeee 8M M8MM8, eee eee eeeeeee eee eeeeeee eeeee eeeeeee eeeeeeee. Meeee eeeeeee eeeeeeeeeeeee ee eM 8, eee eeeeeeeeee eeee MeMe, eee eeeeeee eee eeeeeeeee eeee MeMMe. Mee eeeeeee eee eeeee (MeMM8) eee eeeeeeeeeeee ee eeeeee e eeeeeee eeee eee eeeeeeee ee eeeeeeeeeeeeee (eeeeee eee); eeeee: 888ee (88%).