TY - JOUR
T1 - The formation of a peracetal and trioxane from an enol ether with copper(II) triflate and oxygen
T2 - Unexpected oxygenation of aldol intermediates
AU - Vonwiller, Simone C.
AU - Warner, Jacqueline A.
AU - Mann, Simon T.
AU - Haynes, Richard K.
N1 - Funding Information:
Acknowledgements: We thank the Australian Research Council for financial support. The award of Australian Postgraduate Research Awards (S. T. M. and J. A. W.) and a Queen Elizabeth II Fellowship 1992-1996 (S. C. V.) ate gratefully acknowledged.
PY - 1997/3/31
Y1 - 1997/3/31
N2 - The enol ether 7 undergoes rapid conversion into a 2:3 mixture of cis aldol 9 and trans aldol 11 in the presence of copper(II) triflate (0.1 equiv) and water (1 equiv) in MeCN with no intermediate formation of the corresponding ketoaldehyde 12. In the presence of oxygen, slow oxygenation of the aldols takes place to give the peracetal 13 and bioxane 14 (93:7, 47% combined yield), and the methoxyaldehyde 8 in 12% yield. It is proposed that retroaldolisation to an enol or Cu(II) enolate which is oxidised to an enol radical is the key step. Oxygenation of trans aldol 11 with Cu(II)/O2 in the presence of MeOH gave the peracetal (37%), trioxane (2%), and the methoxyaldehydes 8 (4%) and 10 (4%). The cis aldol 9 reacted, by comparison, very slowly under the same conditions.
AB - The enol ether 7 undergoes rapid conversion into a 2:3 mixture of cis aldol 9 and trans aldol 11 in the presence of copper(II) triflate (0.1 equiv) and water (1 equiv) in MeCN with no intermediate formation of the corresponding ketoaldehyde 12. In the presence of oxygen, slow oxygenation of the aldols takes place to give the peracetal 13 and bioxane 14 (93:7, 47% combined yield), and the methoxyaldehyde 8 in 12% yield. It is proposed that retroaldolisation to an enol or Cu(II) enolate which is oxidised to an enol radical is the key step. Oxygenation of trans aldol 11 with Cu(II)/O2 in the presence of MeOH gave the peracetal (37%), trioxane (2%), and the methoxyaldehydes 8 (4%) and 10 (4%). The cis aldol 9 reacted, by comparison, very slowly under the same conditions.
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U2 - 10.1016/S0040-4039(97)00349-3
DO - 10.1016/S0040-4039(97)00349-3
M3 - Article
AN - SCOPUS:0031592557
SN - 0040-4039
VL - 38
SP - 2363
EP - 2366
JO - Tetrahedron Letters
JF - Tetrahedron Letters
IS - 13
ER -