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Journal ArticleDOI

Benzopyrans. Part 30. Synthesis of substituted xanthones from 3-acyl-2-methyl-1-benzopyran-4-ones

07 May 1993-Tetrahedron (Pergamon)-Vol. 49, Iss: 19, pp 4127-4134
Abstract: The xanthone 8 results from the base catalysed self-condensation of the chromone 1 The chromone 2 gives the xanthones 9 and 11 with sodium and DMF-POCl 3 respectively, phenol 14 with NaOMe, and the pyran 22 with 2-thiomethylchromone 6 The enamine 16 on Vilsmeier-Haak reaction affords the chloroxanthone 12 The pyran 15 , isolated as a byproduct from the reaction of ω-acetyl-2-hydroxyacetophenone with HC(OEt) 3 -Ac 2 O, affords the xanthone 13 by refluxing with NaOMe in MeOH
Topics: Chromone (67%), Pyran (56%), Benzopyran (55%), Xanthone (55%), Benzopyrans (52%)
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Abstract: The Chemistry and application of the title aldehyde and some simple derivatives thereof are reviewed.

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Abstract: Compound that inhibit DNA-dependent protein kinase, compositions comprising the compounds, methods of inhibiting the DNA-PK biological activity, methods of sensitizing cells the agents that cause DNA lesions, and methods of potentiating cancer treatment are disclosed.

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Reference EntryDOI
15 Apr 2004-Organic Reactions
Abstract: This chapter extends the discussion to reactions between the Vilsmeier-Haack reagent (subsequently referred to as the Vilsmeier reagent for brevity) and any other compounds in which a carbon-carbon bond is formed. The discussion thus excludes reactions in which the Vilsmeier reagent acts as a chlorinating agent (for example in the preparation of acid chlorides), or in which it forms carbon-oxygen or carbon-nitrogen bonds, unless these are accompanied by formation of a carbon-carbon bond. For a discussion of the nature of the reagent and of the mechanism of the reaction, the earlier chapter in vol. 49 should be consulted. There are also a number of reviews that deal at length with mechanisms of reactions involving the Vilsmeier reagent, notably those by Jutz and Marson, and hence this chapter will concentrate on applications, with brief mention of mechanisms when necessary. Wizinger has pointed out that alkenes could react with the Vilsmeier reagent, but his only examples were styrenes where the intermediate carbocation has considerable stability. Hydrolysis gives the cinnamaldehyde. In principle, any alkene which is not too sterically hindered can undergo this reaction, but the Vilsmeier reagent has low reactivity as an electrophile, and in practice activation is often necessary. The addition depends on the HOMO of the alkene, and anything increasing the HOMO energy will aid reaction, as for example further conjugation (dienes, trienes, etc.) or the presence of an electron-donating substituent. Hence aldehydes and ketones are active in their enol forms, and enol ethers and enamines are good substrates. Indeed, all additions covered by this chapter can be regarded as alkene additions, even those on active methyl groups attached to electron-deficient rings. As with any reaction involving carbocation intermediates, rearrangements are possible; the initial products are sometimes enamines, and this can give rise to polysubstitution. The substrates are grouped into eleven major subsections; references to reviews of particular relevance will be found in the appropriate subsection. Keywords: vilsmeier reaction; non-aromatics; alkenes; dienes; polyenes; heteroatoms; substituents; enamines; enamides; alkynes; aldehydes; ketones; imines; hydrazones; semicarbazones; oximes; carboxylic acids; anhydrides; acid chlorides; esters; lactones; amides; lactams; imides; nitriles; methyl groups; methylene groups; adjacent rings; comparison of methods; experimental conditions; experimental procedures; tabular survey

29 citations


References
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Journal ArticleDOI
01 Jan 1979-Tetrahedron
Abstract: The 13 C NMR chemical shifts of eleven hydroxy-, two hydroxymethoxy xanthones, and xanthone- C -glucoside, mangiferin, are presented and analyzed. Hydroxy substituent effects depending on substituent position as well as on shielded ring carbon position have been evaluated. Hydroxy substituent increments for xanthones are proposed. Effects of hydroxylation on carbonyl carbon shift and the methylation of hydroxy group and the corresponding shift increments which are of diagnostic value have been observed and discussed.

71 citations


Journal ArticleDOI
01 Jan 1987-Tetrahedron
Abstract: The benzopyranones 1 and 3 reacted with 2,3-dimethyl-1,3-butadiene in the presence of titanium (IV) chloride to give the corresponding (4 + 2) cycloadducts 8 and 11 , the former undergoing facile deformylation to give 9 and 10 . Compounds 1 , 3 , and 4 underwent efficient uncatalysed cycloaddition to 1- methoxy-3-(trimethylsilyloxy)-l,3-butadiene 12 to give the respective adducts 13,14 , and 18 as mixtures of C-l stereoisomers. Heating the 3-arylsulphinylchromone 5 with the diene 12 afforded 3-hydroxyxanthone 23 in 50% yield, the presumed cycloaddition - elimination sequence constituting a new route to xanthone systems. Desilylation of 13,14 , and 18 in acidic media provided 25,26 , and 27 respectively.

55 citations


Journal ArticleDOI
Abstract: In 2-Stellung unsubstituierte 3-Acyl-chromone wurden aus 2-Hydroxy-ω-acyl-acetophenonen durch Reaktion mit Orthoameisensaure-triathylester und Acetanhydrid oder aus 2-Hydroxy-ω-formyl-acetophenon und Acetanhydrid/Natriumacetat dargestellt. Strukturbeweise wurden mit Hilfe von UV-, IR- und NMR-Spektren gefuhrt.

36 citations


Journal ArticleDOI
Abstract: Die 3-Acyl-2-methylthio-chromone 5a, 5c und 5d reagieren mit Hydroxid- und Alkoxidionen sowie Aminen unter Verdrangung der Methylthio-Gruppe zu den in 2-Stellung substituierten 3-Acyl-chromonen 8 und 10a–10p bzw. den 3-Acyl-4-hydroxy-cumarinen 6a und 6b. Mit Hydrazin, Hydroxylamin, o-Phenylendiamin, Guanidin und Amidin-Derivaten entstehen die anellierten Chromone 11a–11c, 12, 13 und 14a–14e.. Synthesis and Reactions of 3-Acyl-2-(methylthio)chromones 3-Acyl-2-(methylthio)chromones 5a, 5c and 5d react with hydroxide or alkoxide ions or with amines to yield the substituted 3-acylchromones 8, 10a–10p, or the 3-acyl-4-hydroxycoumarins 6a and 6b. With hydrazine, hydroxylamine, o-phenylenediamine, guanidine or amidine derivatives the fused chromones 11a–11c, 12, 13 and 14–14e are obtained.

25 citations


Journal ArticleDOI
Abstract: Die 3-Acyl-2-methylthio-chromone 2a-2c und das 6-Acetyl-7-methylthio-furochromon 10 setzten sich mit den CH-aciden Verbindungen 5a-5f, 11 und Kalium-t-butylat zu den 2-substituierten 3-Acylchromonen 4a-4d und 9, den Xanthonen 1 und 6a-6d sowie den Furoxanthonen 13a-13c und 20 um. 4b und 4c reagierten mit Ammoniumacetat zu den Benzopyranopyridinonen (Azaxanthonen) 8a und 8b. Xanthones from Chromone Derivatives The 3-acyl-2-(methylthio)chromones 2a-2c and the 6-acetyl-7-(methylthio)furochromone 10 react with the CH-acidic compounds 5a-5f, 11 and potassium tert.-butylate to yield the 3-acylchromones 4a-4d and 9, the xanthones 1 und 6a-6d and the furoxanthones 13a-13c and 20. With ammonium acetate, 4b and 4c gave the benzopyranopyridinones (azaxanthones) 8a-8b.

16 citations


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