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2005
Furan derivatives
R 0060
Conjugate Addition of Organocopper Reagents to γ-Alkoxybutenolides and Apto the Synthesis of Non-racemic Alkyl Cyclopentenones. — The anti-se10- 105 plication
lective 1,4-addition of simple alkyl copper reagents to γ-alkoxybutenolides (I) in the
presence of BF3·Et2O is presented. Under the acidic conditions, the acetal centre is
epimerized affording the minor diastereomer (IV). Enolate alkylation of the adducts
leads to di- and trisubstituted lactones which are converted into cyclopentenones like
(VIII) and (X) via tandem lactone cleavage and Horner-Wadsworth-Emmons reaction.
The latter reaction is sensitive to the steric environment around the lactone and only in
favorable cases successful and thus no general practical route to alkylpentenones. —
(ROBERTSON*, J.; MENARD, M.; FORD, R.; BELL, S.; Org. Biomol. Chem. 2
(2004) 20, 2988-2997; Chem. Res. Lab., Dep. Chem., Univ. Oxford, Oxford OX1 3TA,
UK; Eng.) — Bartels
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