Benzofuran derivatives. Part 3 On the reactivities of the intermediates in benzofuran synthesis

• DOI: 10.1002/jhet.5570240414
• Publication Date: 2009-04-06T17:52:58Z
• Authors: Takaaki Horaguchi; Shinichi Matsuda; Kiyoshi Tanemura; Tsuneo Suzuki
• Keywords: 01 natural sciences; 0104 chemical sciences

Abstract3‐Methyl‐5‐nitrobenzofuran (2) and 3‐methyl‐5‐nitrobenzofuran‐2‐carboxylic acid (3) were obtained by heating 2‐acetyl‐4‐nitrophenoxyacetic acid (1) with various bases in acetic anhydride. It appeared that 3‐hydroxy‐3‐methyl‐5‐nitro‐2,3‐dihydrobenzofuran‐2‐carboxylic acid (4) was the intermediate in the benzofuran synthesis. The properties of 4 were examined under various conditions. Using strong bases such as triethyl‐amine in place of sodium acetate, 3‐methyl‐5‐nitrobenzofuran‐2‐carboxylic acid (3) was obtained exclusively. However, in the presence of acetic acid in the reaction mixture 3‐methyl‐5‐nitrobenzofuran (2) was obtained in good yield. The reaction pathways for the formation of 2 and 3 are discussed.