D. D. Rijke, H. Boelens
Sep 4, 1973
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ChemInform
Abstract
2-Alkyl-4-ethoxycarbonyl-5-methyl-3-oxo-2H-furans (I, R′ = Et) can be prepared at − 20° from ethyl acetoacetate and α-bromo carboxylic acid chlorides. The furans do not enolize to hydroxyfurans, but behave essentially as unsaturated ketones towards various nucleophiles. With potassium hydroxide, ring opening and closure leads ultimately to 3-acetyl-5-alkyl-4-hydroxy-2-oxo-5H-furans (II); with sodium methoxide the overall process is one of decarboxylation while oxidative decarboxylation with hydrogen peroxide in an alkaline medium yields 2-alkyl-4-hydroxy-5-methyl-3-oxo-2H-furans (IV). As illustrated in Scheme 1 all three processes are thought to be initiated by the addition of a nucleophile (HO−, CH3O−, HOO−) on the activated double bond in the furans.