2005

Furan derivativesR 0060 Conjugate Addition of Organocopper Reagents to γ-Alkoxybutenolides and Ap-

plication to the Synthesis of Non-racemic Alkyl Cyclopentenones. — The anti-se-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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