Eco-friendly synthesis of fused pyrano[2,3-b]pyransviaammonium acetate-mediated formal oxa-[3 + 3]cycloaddition of 4H-chromene-3-carbaldehydes and cyclic 1,3-dicarbonyl compounds
Various substituted polycyclic pyrano[2,3-b]pyrans were synthesizedviathe condensation of 4H-chromene-3-carbaldehydes and their areno-condensed analogues with hetero- and carbocyclic 1,3-dicarbonyl compounds in acetic acid. Ammonium acetate was used as a green catalyst for the reaction. The process...
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| Главные авторы: | , |
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| Formato: | Статья |
| Idioma: | English |
| Publicado: |
Royal Society of Chemistry
2020
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| Acceso en liña: | https://dspace.ncfu.ru/handle/20.500.12258/14526 |
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| Краткое описание: | Various substituted polycyclic pyrano[2,3-b]pyrans were synthesizedviathe condensation of 4H-chromene-3-carbaldehydes and their areno-condensed analogues with hetero- and carbocyclic 1,3-dicarbonyl compounds in acetic acid. Ammonium acetate was used as a green catalyst for the reaction. The process also involves the subsequent Knoevenagel condensation and 6π-electrocyclization of the 1-oxatriene intermediates formed. Fused pyridines were isolated as the products of the conjugated addition of ammonia to 1-oxatriene intermediates while using carbocyclic 1,3-dicarbonyl compounds and increasing the reaction time, indicating the reversibility of the electrocyclization stage. The calculated values of the Gibbs free energies and reaction rate constants for the 1-oxatriene - 2H-pyran equilibrium also testified to the irreversibility of pyrano[2,3-b]pyran formation in the case of using of heterocyclic 1,3-dicarbonyl compounds |
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