- Benzofuran Derivatives. Part 4. Synthesis of Benzofurans and 2,3,4,5-Tetrahydro-1-benzoxepin-3,5-diones
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By treatment of ethyl 4- or 5-substituted 2-acetylphenoxyacetates 1 with potassium hydroxide in dry dioxane, benzofurans 2-7 and 2,3,4,5-tetrahydro-1-benzoxepin-3,5-diones 8 were obtained.The relative yields of benzofurans 2-7 and 2,3,4,5-tetrahydro-1-benzoxepin-3,5-diones 8 varied with the types of 4- or 5-substituents.The electron-donating 4-methoxyl group favored the formation of benzoxepins.On the other hand, electron-withdrawing substituents such as the 4-nitro group favored the formation of benzofurans.When esters 1 were treated with sodium amide,2,3-dihydrobenzofurans 2 were obtained exclusively regardless of 4- or 5-substituents.
- Suzuki, Tsuneo,Tanemura, Kiyoshi,Horaguchi, Takaaki,Shimimizu, Takahachi,Sakakibara, Tohru
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p. 423 - 429
(2007/10/02)
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- BENZOFURAN DERIVATIVES. I. ON THE EFFECTS OF SUBSTITUENTS IN BENZOFURAN SYNTHESES.
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The Roessing's reaction of 4-substituted 2-acylphenoxyacetic acids give a mixture of benzofurans and 2-benzofurancarboxylic acids. The relative yields of benzofurans and 2-benzofurancarboxylic acids depend on the substituents on the benzene ring of the 2-acylphenoxyacetic acids. Electron-withdrawing substituents such as nitro groups favor the formation of 2-benzofurancarboxylic acids. On the other hand, the formation of benzofurans is favored by the steric hindrance of 2-acyl groups in the reaction of 2-acyl-4-nitrophenoxyacetic acids with anhydrous sodium acetate and acetic anhydride.
- Suzuki,Horaguchi,Shimizu,Abe
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p. 2762 - 2767
(2007/10/02)
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