The formation of a peracetal and trioxane from an enol ether with copper(II) triflate and oxygen: Unexpected oxygenation of aldol intermediates
✍ Scribed by Simone C. Vonwiller; Jacqueline A. Warner; Simon T. Mann; Richard K. Haynes
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- French
- Weight
- 311 KB
- Volume
- 38
- Category
- Article
- ISSN
- 0040-4039
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✦ Synopsis
The enol ether 7 undergoes rapid conversion into a 2:3 mixture of cis aldol9 and trans aldol 11 in the presence of copper(X) triflate (0.1 equiv) and water (1 equiv) in MeCN with no intermediate formation of the corresponding ketoaidehyde 12. In the presence of oxygen, slow oxygenation of the aldols takes place to give the peracetal 13 and trioxane 14 (93:7, 47% combined yield), and the methoxyaldehyde 8 in 12% yield. It is proposed that retroaldolisation to an en01 or Cu(II) enolate which is oxidised to an en01 radical is the key step. Oxygenation of trans aldolll with Cu(II)& in the pesence of MeOH gave the peracetal(37%), trioxane (2%). and the methoxyakiehydea 8 (4%) and 10 (4%). The cis aldol9 reacted, by comparison, very slowly under the same wndilions.