A mixture of chroman-4-one (1.00 g, 6.749 mmol), 3,4-difluorobenzaldehyde (1.15 g, 8.099 mmol) and 10–15 drops of piperidine in cyclohexane was heated at80°C for 24 hrs. The reaction mixture was monitored for completion by thinlayer chromatography. Upon completion, the reaction mixture was cooled,diluted with water and neutralized using 10% HCl. The reaction mixture wasextracted with ethyl acetate (3 × 30 ml). The ethyl acetate layers werecombined, washed with brine (20 ml), water (2 × 10 ml) and dried overanhydrous magnesium sulfate. The solvent was reduced and the compound purifiedby column chromatography using silica gel (Merck 9385, 40–63 µmparticle size) with a mobile phase of 2% ethyl acetate in hexane to yield thetitle compound.
In the molecular structure, the dihedral angle between the fluorinated benzenemoiety and the benzene ring of the chromanone moiety is 37.30°. Thecyclohexane moiety on the fluorinated benzene ring is attached to the leaststerically hindered para-position of the phenyl ring and adopts a chairconfirmation.
The chroman-4-one (2,3-dihydro-4-oxo-4-1-benzopyran) ring system occupies an important position among oxygen heterocyclics and features in a wide variety of compounds of biological and medicinal interest (Finch & Tamm, 1970). Many biologically active natural products containing a chroman ring system have been synthesized 2-substituted chroman-4-one intermediates including alpha-tocopherol (vitamin E) (Geen , 1996). 3-arylidene-4-chromanones have also been isolated as natural products belonging to the class of compounds called homoisoflavonoids(Tietze & Gerlitzer, 1997).
In the molecular structure, the dihedral angle between the fluorinated benzene moiety and the benzene ring of the chromanone moiety is 37.30°. The cyclohexane moiety on the fluorinated benzene ring is attached to the least sterically hindered -position of the phenyl ring and adopts a chair confirmation.
A mixture of chroman-4-one (1.00 g, 6.749 mmol), 3,4-difluorobenzaldehyde (1.15 g, 8.099 mmol) and 10–15 drops of piperidine in cyclohexane was heated at 80°C for 24 hrs. The reaction mixture was monitored for completion by thin layer Upon completion, the reaction mixture was cooled, diluted with water and neutralized using 10% HCl. The reaction mixture was extracted with ethyl acetate (3 × 30 ml). The ethyl acetate layers were combined, washed with brine (20 ml), water (2 × 10 ml) and dried over anhydrous magnesium sulfate. The solvent was reduced and the compound purified by using silica gel (Merck 9385, 40–63 m particle size) with a mobile phase of 2% ethyl acetate in hexane to yield the title compound.
Methyl-(2)-2-bromo methyl-3-aryl prop-2-enoate (0.006 mole, 1.53 g) was treated with 4-methoxy phenol (0.006 mole, 0.9 ml) in the presence of potassium carbonate in acetone at reflux temperature for 3 hrs. The pure ester, 3-aryl-2-(4-methoxy)-phenoxymethylprop-2-enoate was obtained after purifying it using silica gel and (3% ethyl acetate - hexane). Hydrolysis of this ester was carried out with KOH in aqueous 1,4–dioxane at room temperature. The reaction mixture was acidified and the precipitated acid was purified by recrystalization. Finally the acid was treated with triflouroacetic anhydride and the reaction mixture was refluxed in dichloro- methane for 1 hr. It was further purified by (silica gel-3% ethyl acetate - hexane) and the crystals used for data collection were obtained by slow evaporation from methanol.
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The title compound, 3-(4-cyclohexyl-3-fluorobenzylidene)chroman-4-one, belongs to the homoisoflavonoid class of compounds, which are , unsaturated containing two aromatic rings. They are a group of naturally occurring molecules that are structurally related to but differ by containing one more carbon atoms (Kirkiacharian , 1984). This compound may undergo chemical conversion into the (E)- and ()-isomers (Kirkiacharian , 1984). The 3-benzylidene-4-chromanones have been shown to display a wide range of biological activities (du Toit , 2010). The most commonly used procedure for the synthesis of homoisoflavonoids involves the condensation of chroman-4-one with an aromatic aldehyde in the presence of an acidic or basic catalyst (Shaikh , 2011). We have recently been involved in the synthesis and characterization of fluorinated homoisoflavonoids in the search for lead pharmaceuticals (Gopaul , 2012).
Methanol, ethanol, and acetone extracts showed effective antimicrobial activity against the bacterial.
• : Brazilein, an important immunosuppressive component of CS showed inhibition of T cell proliferation and suppress mice humoral immune response.
Results suggest CS extract may be proposed as a dietary supplement for the prevention of oxidative damage or DNA damage by hydroxyl radicals.
• :Study of aqueous MeOH extracts isolated pure compounds sappanchalcone and brazilin which showed remarkable anticonvulsant activity.
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of yielded six constituents with neuraminidase inhibitory activity: Brazilein, brazilin, protosappanin A, 3-deoxysappanchalcone,
sappanchalcone and rhamnetin.
The synthesis of a range of novel 2,2-disubstituted chroman-4-ones has been accomplished by the pyrrolidine catalysed condensation of a 2-hydroxyacetophenone with aldehydes and ketones. The reaction permits access to both symmetrically and unsymmetrically substituted compounds. The reaction has been extended to the preparation of a novel furochromanone, an analogue of the natural product khellin.
The Schmidt reaction of 2,2-disubstituted chroman-4-ones in an acetic-sulphuric acid mixture affords 2,3,4.5-tetrahydro-1.4-
benzoxazepine-5(411)--ones, resulting from alkyl migration of the iminodiszonium intermediate. Chroman-4-ones possessing a carbocation stabilising function show anomalous behaviour, the initially formed 1,4-benzoxazepinone being particularly
susceptible to protolysis. 2-Methyl-2-phenylchromanone affords a 2-oxazoline as the major product, whilst 2-cyclopropyl-2-
methylchromanone gives a mixture of five components which have been separated and characterised. The major products result from hydration and acetolysis of the cyclopropyl carbenium ion.
Products resulting from aryl migration and anti-Markovnikov addition of acetic acid to the cyclopropane ring are also formed.
Carbanions derived from chromanones have been generated and used to prepare a range of 3-hydroxymethylenechroman-4-ones. Conjugate reduction of the corresponding chromone by sodium borohydride in pyridine provides a simple entry to 3-acetyl and 3-aroyl-2-methylchromanones. These dicarbonyl compounds are versatile intermediates and have been used to prepare a range of benzopyrano isoxazoles, pyrazoles. pyrroles and pyrimidines.
3-Hydroxymethylenespiro[chroman-2. 1 '-cyclopentan]-4-one is particularly unstable to acid-base conditions. Attempts to
prepare this compound resulted only in the formation of 3-(1 cyclopentenyl)chromone, arising from a bond-switch operation
initiated by fragmentation of the pyranone ring in a retro-Michael reaction. Conditions suitable for extension of this reaction to other 3-hydroxymethylenechromanones have been developed, affording access to a range of hitherto inaccessible 3-alkenylchromones.
The regio- and stereo-chemical outcome of the reaction has been elucidated.
Some preliminary investigations of the behaviour of 3-alkenyl chromones in Diels-Alder reactions are described.