3-Alkoxy-2,5-dihydrofurans by gold-catalyzed allenyl cyclizations and their transformation into 1,4-dicarbonyl compounds, cyclopentenones, and butenolides

Article abstract of DOI:10.1055/s-0030-1258265

The addition of lithiated alkoxyallenes to carbonyl compounds furnishes allenyl alcohols, which undergo a highly efficient and chemoselective 5-endo-trig cyclization to 3-alkoxy-2,5-dihydrofurans catalyzed by gold(I) chloride. The dihydrofurans produced can be either oxidized to -alkoxy butenolides by a manganese(III) acetate catalyzed radical oxidation with tert-butyl hydroperoxide, or transformed into ,-unsaturated -keto aldehydes by an oxidative ring cleavage using DDQ in the presence of water. Treatment of the -keto aldehydes with sodium methoxide in methanol promotes a diastereoselective intramolecular aldol addition furnishing alkoxy-substituted cyclopentenone derivatives in good yield. Georg Thieme Verlag Stuttgart · New York.