Coumarin-3-carboxylic acids

Coumarin-3-carboxylic acid, 4-hydroxy-ethyl ester... 

Coumarin-3-carboxylic acid, 6-nitro-ethyl ester reduction, 3, 691 Coumarinic acid synthesis, 3, 685 Coumarinoisocoumarin synthesis, 3, 834 Coumarins acetoxylation, 3, 680 acylation, 3, 689 annelated... 

Bigi F, Chesini L, Maggi R, Sartori G (1999) Montmorillonite KSF as an inorganic, water stable, and reusable catalyst for the knoevenagel synthesis of coumarin-3-carboxylic acids. J Org Chem 64 1033-1035... 

Song A, Wang X, Lam KS (2003) A convenient synthesis of coumarin-3-carboxylic acids via Knoevenagel condensation of Meldrum s acid with ortho-hydroxyaryl aldehydes or ketones. Tetrahedron Lett 44 1755-1758... 

Grinding thiadiazolamines 101 with an equivalent of coumarin-3-carboxylic acid chloride 100 under solvent-free conditions in a mortar gave the corresponding amides 102 in 76-90% yields, or when heated in a microwave oven for 5-18min in 87-93% yields (Equation 29) <2006PS183>. 

Somewhat unexpectedly, the 1-dansylamino derivative 193 (Scheme 58) of the 3-glucosidase inhibitor 2,5-dideoxy-2,5-imino-D-mannitol turned out a nanomolar inhibitor (K 2.4 nM) of Agrobacterium sp. (3-glucosidase.382 The same was true when the fluorophor and the inhibitor were separated by a C6 spacer arm. Equally active were the corresponding coumarin-3-carboxylic acid derivative 66 (Scheme 18 ... 

The Pechmann and Knoevenagel reactions have been widely used to synthesise coumarins and developments in both have been reported. Activated phenols react rapidly with ethyl acetoacetate, propenoic acid and propynoic acid under microwave irradiation using cation-exchange resins as catalyst <99SL608>. Similarly, salicylaldehydes are converted into coumarin-3-carboxylic acids when the reaction with malonic acid is catalysed by the montmorillonite KSF <99JOC1033>. In both cases the use of a solid catalyst has environmentally friendly benefits. Methyl 3-(3-coumarinyl)propenoate 44, prepared from dimethyl glutaconate and salicylaldehyde, is a stable electron deficient diene which reacts with enamines to form benzo[c]coumarins. An inverse electron demand Diels-Alder reaction is followed by elimination of a secondary amine and aromatisation (Scheme 26) <99SL477>. 

Coumarin-3-carboxylic acid [531-81-7J M 190.2, m 188"(dec). Crystd from water. 

Manevich Y, Held KD, Biaglow JE (1997) Coumarin-3-carboxylic acid as a detector for hydroxyl radicals generated chemically and by gamma radiation. Radiat Res 148 580-591 Maples KR, Johnson NF (1992) Fiber-induced hydroxyl radical formation correlation with mesothelioma induction on rats and humans. Carcinogenesis 13 2035-2039 MarkG, Korth H-G, Schuchmann H-P, von Sonntag C (1996) The photochemistry of aqueous nitrate revisited. J Photochem Photobiol A Chem 101 89-103 Maskos Z, Rush JD, Koppenol WH (1990) The hydroxylation of the salicylate anion by a Fenton reaction and v-radiolysis a consideration of the respective mechanisms. Free Rad Biol Med 8 153-162... 

A new type of photo-dimerization reaction for coumarin derivatives has also been described (Equation 16) <2002TL5161>. Irradiation of coumarin-3-carboxylic acid 180 in ethanol provided three different types of products the 4,4 -dimer of chroman-2-one 181, 3-(l -hydroxyethyl)-coumarin 182, and coumarin 183. The authors postulated that for the formation of 181, a ketyl radical is first formed, and the equilibrium between the 2-position and 4-position radical favors the latter. Dimerization of the 4-position radicals, followed by tautomerization and decarboxylation, provides dimer 181. 

Salicylaldehydes and some o-hydroxyaryl ketones react with Meldrum s acid to give coumarin-3-carboxylic acids <03TL1755>. 3-Cyanocoumarins, and thus the 3-carboxylic acids, are available in high yield from a Knoevenagel reaction between salicylaldehydes and malononitrile in water <0382331>. 3-Chlorocoumarins result from the cathodic reduction of trichloroacetyl esters of o-hydroxyacetophenones <03T9161>. 

Li et al. [30] gave the solvent free synthesis of 2-aryl-5-(coumarin-3 -yl)-l,3,4-oxadiazoles (xxv) in high yields by reacting the coumarin-3-carboxylic acid (xxiii) with (un)substituted benzoic acid hydrazides (xxiv) in presence of PEG supported dichlorophosphate under microwave irradiation. 

We have been particularly enamored with the development of experiments involving carbon-carbon bond formation, especially as part of tandem reactions occurring in a single container (see the Diels-Alder reaction. Figure 1). One such reaction is the synthesis of simple esters of coumarin-3-carboxylic acids via a Knoevenagel condensation between malonic esters and various a-hydroxybenzaldehydes, followed by intramolecular nucleophilic acyl substitution. This conversion, catalyzed by piperidine, has been carried out under a variety of conditions, for example, at room temperature without solvent... 

Boehm [363] has described for the first time the synthesis of oxygen-bridged tetrahydropyridones by a three-component condensation among coumarin-3-carboxylic acid, ketones, and primary amines. A solid-phase version of this reaction has recently been reported [364]. 1,3-Propylenediamine was immobilized onto chloro-trityl polystyrene resin (loading of 0.65 mmol g ). The supported amine (470) was then treated with coumarin-3-carboxylic acid and 8 different ketones in NMP/THF... 

Coumarins are known to react with amines to give various products, for example 2,3-dihydrobenzofurans. 3-Bromocoumarin has been shown to give the benzofuran (194) on heating with piperidine but coumarin itself gave 2 -hydroxycinnamic acid amides. The behaviour of coumarin-3-carboxylic acid with amines depends on the ratio of reactants and the temperature. When 8-acetyl-7-hy(iroxy-4-methylcoumarin was subjected to a Mannich reaction, the benzodipyran (195) was formed in 80% yield.Several other tricyclic products have been prepared from coumarins for example, the... 

Coumarin-3 carboxylic Acid 2-Oxo-2H-I benzo-pyran-3-carbojeytic acid, mol wt 190.15. C... 

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