4- Hydroxy coumarin, addition

Haywood, D.J., Hunt, R.G., Potter, C.J., and Reid, S.T. (1977) Photochemical transformations. Part 10. Photocydo-addition reactions of 4-hydroxy-coumarin with cycloalkenes. Journal... 

The changes in the spectral parameters of hydroxycoumarins brought about by the addition of acids or bases are of value in structural elucidation (60JOC2183, 67JCS(C)2545>. For example, both 5- and 7-hydroxy coumarins show red shifts and increases in intensity upon the addition of base, whereas for the 6- and 8-substituted compounds the bathochromic shift is accompanied by a reduction in intensity (69JCS(C)526>. Several other additives have proved useful in structure elucidation, notably sodium acetate (66IJC120) and aluminum chloride (69MI22201). ... 

Most of the imprinted sorbents used in MISPE were prepared using MAA and ethylene glycol dimethacrylate (EDMA) as monomers. In these cases elution of more weakly bound analytes such as triazines [19,30,32], 7-hydroxy-coumarin (2) [26] or theophylline (12) [28] can be achieved using methanol or water as elution solvent. For more strongly bound analytes such as stronger nitrogen Bronsted bases, efficient elution has been achieved using eluents of the same base solvent but with the addition of small amounts of acids (e.g. acetic acid, trifluoroacetic acid (TEA)) or base (e.g. triethylamine (TEA)) [20-22,25,33]. 

The photodecarboxylation of chromone-2-carboxylic acid in aerated and deaerated ethanol solution was studied by TR EPR and the chemiluminescence technique. The two reaction products 4-hydroxy-coumarin and 2-(F-hydroxyethyl)chromone are generated through the addition of ground-state oxygen molecules to the excited flavone, and through recombination between ketyl radicals and 1-hydroxyethyl radicals followed by the release of CO2, respectively. An anomalous CIDEP behaviour of the ketyl radical was observed by the addition of hydrochloric acid in the photoreduction of chromone-2-car-boxylic acid. The effects observed are explained by the simultaneous reactions... 

Mei RQ, Xu XY, Li YC, Fu JY, Huang (JC, Wang LX. Highly effective and enantioselective Michael addition of 4-hydroxy-coumarin to a, p-unsaturated ketones promoted by simple chiral primary amine thiourea bifunctional catalysts. Tetrahedron Lett. 2011 52(14) 1566-1568. 

The succinct synthesis of warfarin starts with condensation of ort/zo-hydroxy-acetophenone (1-2) with ethyl carbonate to give the (3-ketoester (1-3) as the presumed intermediate shown in the enol form. Attack of the phenoxide on the ester grouping will lead to cyclization and the formation of the coumarin (1-4). Conjugate addition of the anion from that product to methyl styryl ketone (1-5) gives the corresponding Michael adduct and thus warfarin (1-6) [1]. 

The simple coumarin nucleus (Fig 7.3), which is derived by lactone formation of an ortho-hydroxy-czs cinnamic acid, is a common metabolite in higher plants and is often found in glycosidic form. Coumarins are common in Api-aceae, in certain genera of Fabaceae (e.g. Dipteryx odorata, Melilotus officinalis), Poaceae (e.g. Anthoxanthum odoratum) and Rubiaceae (e.g. Galium odoratum). However, proliferation of coumarins to the status of major chemical markers occurs in only a few cases, most notably, but not exclusively, in the Api-aceae (subfamily Apioideae) and in the Rutaceae (Gray and Waterman, 1978 Murray et al., 1982). In these cases, the coumarin nucleus has almost invariably been embellished by the addition of a prenyl unit leading to furocoumarin (Fig 7.3) and pyranocoumarin structures. 

Addition of a proton to carbonyl oxygen produces a hydroxy-benzopyrylium salt chromones undergo this protonation more easily than the coumarins, for example passage of hydrogen chloride through a mixture of chromone and coumarin in ether solution leads to the precipitation of only chromone hydrochloride (i.e. 4-hydroxy-1-benzopyryhum chloride). O-AUcylation requires the more powerful alkylating agents ... 

In a study of C. arietinum to identify flavonoids the ground up aerial parts were extracted and analysed. In addition to 14 and 69 already previously identified in the species the authors made the first record of coumarins in the genus, specifically scopoletin (7-hydroxy-6-methoxycoumarin) (228) and umbelliferone (7-hydroxycoumarin) (229) [95]. 

The initial concern in the early 1960s about the addition of coumarin 1 to tobacco products was whether or not it was converted during the smoking process to dicumarol (3,3 -methylene-bis[4-hydroxy-2//-l-benzopyran-2-one]) II (Figure VI-I). Dicumarol is a powerful anticoagulant that had been identified in sweet clover hay (6A21). 

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