New data on the reactivity of 2-unsubstituted 3-halochromones

Sosnovskikh, Vyacheslav Ya.

doi:10.1007/s10593-020-02653-0

Cited by 10 publications

(5 citation statements)

References 45 publications

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“…It has to be noted, that the corresponding ring-opening product was observed by 1 H NMR and GC-MS analysis of the crude reaction mixture, considering the tendency of 3iodochromone (1) to undergo, in the presence of Nnucleophiles, an aza-Michael addition/ring-opening/deiodination process as a side reaction (Scheme 2). 26 In the next step, detailed optimization study of our model reaction was performed. The effect of carbon monoxide pressure, the type of the ligand, and the influence of solvent, temperature, and base, on palladium-catalyzed carbonylative process were studied (Table 1).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Synthesis of Chroman-2,4-diones via Ring-Opening/Ring-Closing Reaction Involving Palladium-Catalyzed Intramolecular Aryloxycarbonylation

Chniti,

Pongrácz,

Kollár

et al. 2024

J. Org. Chem.

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Palladium-catalyzed aminocarbonylation of 3-iodochromone was studied in the presence of primary and secondary amines using atmospheric pressure of carbon monoxide as a carbonyl source. This procedure successfully provided a library of chromone-3-carboxamides and 3-substituted chroman-2,4-diones in 40 to 92% isolated yields. The reaction proceeded via highly chemoselective aminocarbonylation (up to 100%) in the presence of secondary amines by using monodentate or bidentate phosphine ligands. The tendency of 3-iodochromone substrate to undergo ANRORC rearrangement with N-nucleophiles was crucial to shift the reaction toward an unprecedented chemoselective carbonylative transformation, where a late-stage carbonyl insertion is favored concomitantly to the last ring-closure step. The proposed aza-Michael addition/ring-opening/intramolecular aryloxycarbonylation sequence showed compatibility, uniquely, to primary amines when XantPhos was used as a ligand. The solid-state structures of chromone-3-carboxamide (2a) and chroman-2,4-dione (3s) were undoubtedly established by single-crystal XRD analysis. A catalytic cycle was proposed to rationalize the formation of the two types of carbonylated compounds.

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Section: ■ Results and Discussionmentioning

confidence: 99%

“…It has to be noted, that the corresponding ring-opening product was observed by 1 H NMR and GC-MS analysis of the crude reaction mixture, considering the tendency of 3-iodochromone ( 1 ) to undergo, in the presence of N -nucleophiles, an aza-Michael addition/ring-opening/deiodination process as a side reaction ( Scheme 2 ). 26 …”

Section: Resultsmentioning

confidence: 99%

Synthesis of Chroman-2,4-diones via Ring-Opening/Ring-Closing Reaction Involving Palladium-Catalyzed Intramolecular Aryloxycarbonylation

Chniti,

Pongrácz,

Kollár

et al. 2024

J. Org. Chem.

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“…[4][5] The presence of halogen atoms in position 3 of the chromone allows its conversion to 2-or 3-substituted chromones, [6][7][8][9] as well as the synthesis of other oxygen-containing heterocycles such as coumarones, chromanones, and furans and nitrogen-containing heterocycles such as imidazoles, pyrroles, pyrimidines, and pyridines. [10] The synthesis of 3-halochromones is usually performed from enaminones [11][12][13][14][15][16][17] due to their easy availability and good shelf stability. [18] The protocols provide an in situ electrophilic halogen species employing N-chlorosuccinimide (NCS) or N-bromosuccinimide (NBS), [12] HX/DMSO, [13] KX/PhI(OAc) 2 , [14] electrochemical oxidation of NaX [15] or other halogen sources as Br 2 [11] or t-butyl hypochlorite, [11] as depicted in Scheme 1.…”

Section: Introductionmentioning

confidence: 99%

“…Among the set of functionalised derivatives, the 3‐halochromones stand out as an easily obtainable building block that can undergo a broad range of chemical transformations [4–5] . The presence of halogen atoms in position 3 of the chromone allows its conversion to 2‐ or 3‐substituted chromones, [6–9] as well as the synthesis of other oxygen‐containing heterocycles such as coumarones, chromanones, and furans and nitrogen‐containing heterocycles such as imidazoles, pyrroles, pyrimidines, and pyridines [10] …”

Section: Introductionmentioning

confidence: 99%

3‐Halochromones Through Oxidative α‐Halogenation of Enaminones and its Photophysical Investigation: Another Case of Photo‐induced Partially Aromatised Intramolecular Charge Transfer?

Neto,

Coelho,

Doerner

et al. 2024

Chemistry An Asian Journal

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A versatile synthesis strategy for fluorescent 3‐halo‐4H‐chromen‐4‐one derivatives is reported. The method involves the oxidative α‐halogenation of enaminones performed by an efficient and sustainable oxidation system. The use of Oxone® in combination with KCl, KBr, or KI enables the preparation of 3‐chloro‐, 3‐bromo‐, or 3‐iodo‐4H‐chromen‐4‐one in good to excellent yields, with great functional group tolerance where the protocol is amenable to gram‐scale synthesis. The analysis of the photophysical properties of the presented 4H‐chromen‐4‐one showed absorption in the UV region and fluorescence emission in the violet‐to‐cyan region with a relatively large Stokes shift. In solution, all compounds present a dual fluorescence emission, regardless of the solvent, assigned to a partially aromatised intramolecular charge transfer mechanism, considering the presence of a pseudo‐aromatic ring in the chromone scaffold and the absence of the influence of substituent electronic features in optical behaviour.

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“…Aminochromones 11 reacted with 3-bromochromones 12, in refluxing acetic acid in the presence of Cs2CO3 as inorganic catalyst, producing furo[3,2-c]chromen-4-ones 13, in moderate yields (Scheme 6) 33. …”

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confidence: 99%