Dienamine 1 with W-phenylmaleimide and chromenone 14 as well as 15 produces, through initial [4 + 2]cycloaddition, xanthenones 10 and 18, respectively. Initial Michael addition of 1 to chromenones 14 and 16, and dimethyl acetylenedicarboxylate (DMAD), triggers the formation of xanthenone 19, 4-azaxanthenone 26 and substituted fumarate 49, respectively. Initial [2 + 2]cycloadducts of dienamines 1-3 with electrophilic acetylenes always undergo further transformations. Thus, 1 with DMAD, dibenzoylacetylene and ethyl propiolate (EP) ultimately gives xanthenones 33, 34 and 37, respectively, the latter being admixed with flavone 43. Enamine 2, cyclisable to xanthenone 11, gives 33 and 35 with DMAD, and 37 and 44 with EP. Reaction of 3 with DMAD affords 36 exclusively. © The Royal Society of Chemistry 1999.

C K GHOSH

S BHATTACHARYYA

C GHOSH

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

Journal of the Chemical Society - Perkin Transactions 1

(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

2-Methyl-4-oxo-4H-1-benzopyran-4-one as a synthon in heterocyclic chemistry

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.

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 of the Chemical Society, Chemical Communications

Base catalysed deacylative dimerisation of 3-acetylchromenone: A facile Diels-Alder reaction

Condensation reactions of 4-oxo-4H-[1]benzopyran-3-carbonitriles (1; X = H, CH3, Cl, and Br) with 1, 2-diamines, acetylglycine, and themselves have been investigated. The compounds 1 on being refluxed with ethylenediamine in ethanol give initially 1, 4-addition products that undergo further transformation to 2-amino-3-formylchromones 2 (45-75%) and l, 3, 4, 5-tetrahydro-2-[(2-hydroxybenzoyl)methylene]imidazoles 3 (7-15%). On the contrary, o-phenylenediamine undergoes 1, 2-addition to the nitrile functions of compounds 1 to form intermediate amidines, which on further cyclization and subsequent air oxidation afford 6-amino-7-oxo-7H-[1]benzopyrano[2, 3-fc]-[1, 5]benzodiazepines 12 (22-36%). The nitriles 1 condense with acetylglycine to afford 2-methyl[1]benzo-pyrano[2, 3-6]pyridino[3, 2-d]oxazol-5(5H)-ones 15 (47-54%). When refluxed with ammonium acetate in acetic acid, compounds 1 undergo self-condensation, giving 2-(4-oxo-4H-[l]benzopyran-3-yl)[l]benzopyrano[3, 2-e]py-rimidin-5(5H)-ones 17 in 13-27% yield. 15 and 17 are also obtained by condensation of 2 with acetylglycine and 1, respectively. © 1980, American Chemical Society. All rights reserved.

Journal	Data powered by TypesetJournal of the Chemical Society - Perkin Transactions 1
Publisher	Data powered by TypesetRoyal Society of Chemistry
ISSN	0300-922X