Benzofuran Derivatives. II. Synthesis of 2,3-Dihydrobenzofurans from Ethyl 2-Acylphenoxyacetates

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Abstract Ethyl 3-alkyl-3-hydroxy-5-nitro-2,3-dihydro-2-benzofurancarboxylates were obtained from the reaction of ethyl 2-acyl-4-nitrophenoxyacetates with potassium hydroxide in dry dioxane. The relative ratios of the cis and trans isomers with respect to C-2 and C-3 stereochemistry varied according to the structure of the acyl group. When the acyl group was acetyl, propionyl, or isobutyryl group, the cis isomers (2-alkoxycarbonyl groups and 3-hydroxyl groups are cis) were exclusively obtained in high yields. On the other hand, a nearly equimolecular amount of the cis and trans isomers was obtained from the reaction of 2-formyl derivatives under the same conditions.