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-POCl3 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-Ac2O, affords the xanthone 13 by refluxing with NaOMe in MeOH. © 1993.

C K GHOSH

S SAHANA

A PATRA

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

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

Tetrahedron

(Chemical Equation Presented) The Chemistry and application of the title aldehyde and some simple derivatives thereof are reviewed.

Journal of Heterocyclic Chemistry

Chemistry and application of 4-oxo-4H-1-benzopyran-3-carboxaldehyde

The chromone 5, obtained by bromination of 3-acetyl-2-methylchromone (3), gives [1]benzoxepino[4,3-d]isoxazole (10) and [1]benzoxepino[3,4-c]pyrazole (11), respectively, with hydroxylamine and phenylhydrazine, pyrrolo [3,4-b][1]benzopyran (18) with thiourea, thiazole 19 with thioacetamide, and quinoxaline 21 with o-phenylenediamine.

Journal of Chemical Research

Benzopyrans. Part 451. Reactions of monobrominated 3-acetyl-2-methyl-1-benzopyran-4-one with some binucleophiles

Reaction of dienamine 2 (R = H and Me) with N-phenylmaleimide or chromone 3 gives xanthones 5 and 8, respectively, through initial [4 + 2] cycloaddition, whereas reaction with dimethyl acetylenedicarboxylate affords xanthone 13.

Journal of the Chemical Society - Perkin Transactions 1

Unusual condensation of 2-(2-dimethylaminovinyl)-1-benzopyran-4-one with dimethyl acetylenedicarboxylate: Formation of 2,3-bis(methoxycarbonyl)xanthen-9-one

The enamine (2), prepared from the title benzopyranone (1; R2 = H, Me, and Ph) and dimethylformamide dimethyl acetal, on treatment with ammonia and hydroxylamine gives the fused pyridine (5) and pyridine 2-oxide (10), respectively. Hydrazine, phenylhydrazine, and guanidine undergo initial 1,6-addition to the enamine (2) ultimately giving the pyrazoles (14) and (15), and the pyrimidine (17), respectively. The pyridinioacetamidate (11), prepared from the enamine (2; R2 = Me and Ph) and acetohydrazide, thermolyses to the fused pyridine (5). A refluxing ethanolic solution of the enamine (2; R2 = Me and Ph) with ethyl glycinate forms the ester (18) which on treatment with ethanolic sodium ethoxide produces the azepine (20).

Journal of the Chemical Society, Perkin Transactions 1

Benzopyrans. Part 23. Nitrogen heterocycles fused with or linked to 1-benzopyran from 3-acyl-2-methyl-1-benzopyran-4-one

That the key step in the title reaction is the Diels-Alder addition of 3-acetylchromenone (1) to its acyl-acyl rearranged isomer (9′a) is supported by the formation of 2-salicyloylxanthone (5) from the reaction of (9) with any of the chromenones (1)-(4).

Journal	Tetrahedron
Publisher	-
ISSN	0040-4020