Solutes chromonics

Method A The 2-hydroxyacetophenone (3 mmol) and acyl chloride (3.6 mmol) in PhH (20 ml) are stirred at 80°C with aqueous K,CO, (I0%, 20 ml) and TBA-HS04 (0.5 g, 1.5 mmol) for 2-3 h until the ester is completely formed. The PhH phase is separated, washed with H.O (3 x 20 ml) and dried by azeotropic distillation. Ring closure is effected by the addition of TosOH (1.55 g, 9 mmol) in PhH (20 ml) and azeotropic distillation. The organic solution is washed with aqueous NaHCO, (10%, 50 ml) and evaporated to yield the chromone. 

Chromones with hydroxy or methoxy groups in the aromatic ring show high intensity bands at 240-260 and 290-360 nm. Both bands are red-shifted relative to chromone and in sodium methoxide solution these shifts are enhanced as a result of ionization of the phenolic groups (76JHC211). 

Upon treatment with a base, the activated methyl group in 2-hydroxyacetophenone is converted into a carbanion. Claisen condensation with an ester gives rise to a 1,3-diketone, the sodium salt of which may be isolated although this process is usually unnecessary. Cyclization to the chromone occurs readily in acid solution (Scheme 147). 

A series of new substituted oestradiols has been synthesized. The reaction of oestradiol with acetyl chloride gave the 2-acetyl derivative (133a). Condensation with ethyl formate (see Scheme 11), followed by brief exposure to acid, afforded the steroidal chromone (134). Whereas treatment of (134) with hydrazine hydrate provided the 3 -phenylpyrazole (135), reaction with hydroxylamine yielded a mixture of the 5 -phenylisoxazole (136) and of the isomeric 3 -phenyl-isoxazole (137). When the oxime (133b) was allowed to react with benzenesul-phonyl chloride in pyridine solution, the methylbenzoxazole (138) was obtained. 

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 ... 

Substituted chromones are formed by heating terminal acetylenes with o-iodophenols under carbon monoxide pressure in the presence of palladium[bis(diphenylphosphino-ferrocene)] dichloride e.g. o-iodophenol and phenylacetylene afford 2-phenylchromone (equation 61) ". Acetylenic aldiminium salts undergo cyclization to six-membered nitrogen heterocycles in polar aprotic solvents. Thus heating solutions of 5-(butylamino) pent-1-yne (607), an aldehyde RCHO (R = Me, Et, Ph or C02Et) and tetrabutylammonium iodide in acetonitrile yields the piperidine derivatives 608 and similar reactions of 4-(benzylamino)but-l-yne lead to tetrahydropyridines 609. ... 

Both coumarin and chromone are converted by diborane then alkaline hydrogen peroxide into S-hydroxychroman." Catalytic reduction of coumarin or chromone saturates the C-C double bond. ° For both systems, hydride reagents can of course react either at carbonyl carbon or at the conjugate position and mixtures therefore tend to be produced. Zinc amalgam in acidic solution converts benzopyrones into 4-... 

Nedocromil is a chromone analogue also used by inhalation as an aerosol, primarily in the prophylaxis of asthma and reversible obstructive airway disease. It inhibits release of allergic mediators, and it is effective in a broad range of patients. An ophthalmic solution is available for the treatment of seasonal and perennial allergic conjunctivitis. Other structurally related compounds are not currently available in the United States but are available in other markets. 

For several years our respective groups have investigated the formation of aromatic compounds from carbohydrates in aqueous solution at various pH-values under reflux or hydrothermolytic conditions. For instance, previous papers(1-6) in this series concerned the degradation of hexoses, pentoses, erythrose, dihydroxyacetone, and hexuronic acids to phenolic and enolic components. Of particular interest were the isolation and identification of catechols, an acetophenone, and chromones from pentoses and hexuronic acids at pH 4.5 (1,2). The formation of these compounds, as well as reductic acid(7),was found to be more pronounced than that of 2-furaldehyde(2) under acidic conditions. 

Epoxidation of enone can be carried out in the absence of a metal catalyst in ionic liquid. A basic aqueous solution of hydrogen peroxide behaves as an efficient oxidant both in [bmim][PF6], which is immiscible in water, and in hydrophilic [bmim] [BF4]. Quantitative yields of the corresponding epoxides were obtained after very short reaction times (Scheme 27). The use of H2O2 in ionic liquids is a viable alternative to using water as the solvent. There is a significant rate acceleration when these salts are used as the reaction medium. This strategy has been successfully applied to the epoxidation of chromones and flavonoids in all cases, the reaction was dramatically improved in [bmim] [BF4] compared with standard classical organic sol vents. 

Among vast varieties of lyotropic LCs, chromonic mesophases are the families of new research target starting only about two or three decades ago. The properties are different from those of ordinary lyotropic mesogens of surfactant type. The molecules constitute aromatic(s) in the center, and hydrophilic parts are scattered around the molecules rather than aliphatic structures. Therefore, they are rigid and planar disklike or planklike, rather than micelles of flexible molecular assemblies of ordinary surfactants. The molecules aggregate in solution to form... 

Hydroxylamine reacts with chromone to give different products according to the reaction conditions in dry methanol, hydroxylamine hydrochloride produces chromone oxime in ethanolic solution, ring opening and re-closure produces isoxazoles. Both types of product are formed via adducts in which a nucleophile has added to C-2. In the former case, the oxime is formed not by direct attack on the carbonyl group of the chromone but via a methanol C-2 adduct. 

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