- Benzopyrans : Part 40 - Alumina mediated transformations of 4-oxo-4H-1- benzopyran-3-carbaldehyde, -3-carboxylic acid and their 2-methylhomologues
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In contact with alumina, the title aldehyde 1 (R = H, Me, Cl) gives the chromones 5 and 9,12 whereas the acid 2 affords the chromones 7, 10 and acetophenone 23. Alumina converts the aldehyde 3 to the xanthone 14, and the corresponding acid 4 to the chromone 8 and diketone 24.
- Ghosh, Chandra Kanta,Bhattacharyya, Samita
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p. 166 - 172
(2007/10/03)
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- SOME REACTIONS OF 6-CHLORO-2-METHYL-4H-1-BENZOPYRAN-4-ONE. PART II
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6-Chloro-2-methyl-4H-1-benzopyran-4-one (I) gave the isoxazole derivative IIa on reaction with hydroxylamine hydrochloride. The action of hydrazine and phenylhydrazine on I resulted in pyrazole dervatives IIIa and IIIb, respectively. The reactivity of I with ethyloxalate and aromatic nitroso compounds have been investigated. Phthalide VIIIa derived from the chromone I was synthesised and rearranged easily into phthalone IX upon refluxing with alcoholic sodium methoxide. Cleavage of VIIIa with amines and hydrazine hydrate was studied. Thiation of phthalide VIIIa with either Lawesson's reagent or phosphorous pentasulphide yielded the corresponding thione VIIIe.
- Salem, Mounir A. I.,Hamed, Ashraf A.,El-Shekeil, Ali G.,Qui, A. S. Baba,Madkour, Hassan M. F.
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p. 605 - 618
(2007/10/03)
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- Photolysis of Enol Acetates and α-Bromo Derivatives of o-(Acyloxy)acetophenones
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UV irradiation of enol acetates 3a-g in benzene gives mainly o-(acetoxy)acetophenones 2 and 2-methylchromones 4. Under the same conditions, the dimethyl derivatives 3h and 3i remain unaffected.The α-bromo ketone 5a gives rise to mixtures of o-(acetoxy)acetophenone (2a), the diketone 6, and/or α-acetoxy-o-hydroxyacetophenone (7), depending on the irradiation conditions.The similarities and differences between the two series of experiments, as well as their possible mechanistic implications, are discussed.
- Garcia, Hermenegildo,Martinez-Utrilla, Roberto,Miranda, Miguel A.
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p. 589 - 598
(2007/10/02)
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- Oxidation of 4-Chromanones with Thalium(III) Nitrate
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Treatment of 4-chromanones 1a-g with thalium(III) nitrate in acidic methanol results mainly in dehydrogenation, whereas α-methoxylation and/or Taylor-McKillop rearrangement predominante in trimethyl orthoformate.The mechanistic features of these oxidations are briefly discussed.
- Ciattini, Pier Giuseppe,Morera, Enrico,Ortar, Giorgio
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p. 395 - 400
(2007/10/02)
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