The Stobbe condensation. Part V. The cyclisation of 3-methoxy-carbonyl-cis-4-(2-furyl)but-3-enoic acid and αβ-difurfurylidenesuccinic anhydride to the corresponding benzofuran derivatives
Abstract
3-Methoxycarbonyl-cis-4-(2-furyl)but-3-enoic acid is cyclised by acetic anhydride and sodium acetate to methyl 4-acetoxybenzofuran-6-carboxylate which is transformed into 4-methoxybenzofuran. Alcoholysis of cis-4-(2-furyl)but-3-en-1,3-dicarboxylic anhydride yields α-methoxycarbonylmethyl-trans-β-(2-furyl)acrylic acid, different from the half ester obtained by the Stobbe condensation. However, αβ-difurfurylidenesuccinic anhydride yields on pyrolysis 4-(2-furyl)benzofuran-5,6-dicarboxylic anhydride.