- Access to chromone-3-carboxylic acid via silver mediated coupling of 4-hydroxy coumarin and enol ester
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A silver-mediated aerobic approach to access 2-methyl-chromone-3-carboxylic acid from the reaction of 4-hydroxy coumarin and enol ester in the presence of base has been presented. Mechanistic investigation suggests that the base induced Michael-type addition reaction of 4-hydroxy coumarin to the enol ester resulting the sequential ring opening and closing with the liberation of acetone are the key-steps for the overall transformation. Theoretical calculation of energy of the intermediates by DFT supports the proposed reaction mechanism.
- Mishra, Priyadarshini,Sepay, Nayim,Panda, Niranjan
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- Benzopyrans: Part XX - 4-Oxo-4H-benzopyran-3-carbonitrile/Carboxylic Acid: Change of Their Reaction Courses by a Methyl Substituent at 2-Position
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2-Methyl-4-oxo-4H-benzopyran-3-carbonitriles (1b) and the corresponding carboxylic acids (2b), unlike their 2-unsubstituted analogues (1a) and (2a), give with phenyl hydrazine the hydrazones (6b) and the pyrazoles (13b), respectively.The hydrazones (6b) have been converted into the benzopyranopyrazoles (8b).
- Ghosh, Chandra Kanta,Pal, Chandana
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p. 1288 - 1290
(2007/10/02)
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- The Synthesis of 2-Methylchromone-3-carboxylic Acid
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A new synthesis of 2-methyl-4-oxo-4H-benzopyran-3-carboxylic acid (2-methylchromone-3-carboxylic acid from salicyloyl chloride and the enamine of ethyl acetoacetate, is described and compared with the classical synthesis.
- Charlton, J. L.,Lypka, G.,Sayeed, V.
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p. 593 - 594
(2007/10/02)
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- Substituted chromone-3-carbonitriles, carboxamides and carboxylic acids useful for preventing asthmatic symptoms
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Substituted chromone-3-carbonitriles, carboxamides and carboxylic acids having the structural formula: SPC1 Wherein R1 represents hydrogen, halogen, lower alkyl, hydroxy, lower alkoxy, or acyloxy; R2 represents hydrogen, lower alkyl, fluorinated lower alkyl, alkoxycarbonyl, carboxy, or lower alkyl carboxylic acid; Z represents cyano, carboxy, alkoxycarbonyl, or EQU1 wherein X represents amino, N-lower-alkylamino, hydroxylamino, N-lower-alkylhydroxylamino, ureido, piperidino, or anilino, with the proviso that when R2 represents hydrogen, Z represents cyano or EQU2 wherein X has the same meaning as given above; and wherein R2 and Z together may form a substituted pyrrole ring; and the corresponding non-toxic, pharmaceutically acceptable salts.
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