Pyrans and Fused Pyrans: (ii) Reactivity

Ellis, G. P.

doi:10.1016/b978-008096519-2.00045-x

Cited by 26 publications

(4 citation statements)

References 334 publications

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“…For patriscabrin A, which was isolated in 2018, one can draw a resonance form that is zwitterionic and contains an aromatic substructure, a pyrylium ion (Figure ). , The extended π-system in patriscabrin A also can be viewed as a vinylogous pyrone (Figure ). For lettucenin A, which was first isolated in 1985, one can draw a resonance form that is zwitterionic and contains an aromatic tropylium ion substructure (Figure ).…”

Section: Results and Discussionmentioning

confidence: 99%

Substituent Effects on the Basicity of Patriscabrin A and Lettucenin A: Evolution Favors the Aromatic?

Prasad

Tantillo

2021

ACS Omega

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Section: Results and Discussionmentioning

confidence: 99%

Substituent Effects on the Basicity of Patriscabrin A and Lettucenin A: Evolution Favors the Aromatic?

Prasad

Tantillo

2021

ACS Omega

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“…The presence of the hydroxyl group at position 3 in the pyrone ring was revealed to be crucial in order to easily obtain aromatic carboxylic derivatives. 26 The reaction of 2-pyrones with amines as nucleophiles is usually reported to lead to open-chain derivatives or to pyridones 27,28 (Figure 1a), but if a hydroxyl group is present at position 3 of the ring, this molecule becomes a masked 1,4dicarbonyl derivative and therefore a good candidate for a P−K synthesis of pyrroles. As far as we know, only one example of this reactivity was reported for a 3-hydroxy-2-pyrone derivative toward ammonia, aniline, and 1,2-diaminobenzene in acetic acid to obtain the corresponding pyrrole derivative (Figure 1b).…”

Section: ■ Introductionmentioning

confidence: 99%

Sustainable Synthesis of N-Alkyl-Pyrrolecarboxylic and Pyrrolepyrazinones Derivatives from Biosourced 3-Hydroxy-2-pyrones and Amines

Leonardi

Truscello

Righetti

et al. 2022

ACS Sustainable Chem. Eng.

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Pyrroles are important compounds present in biological systems, used for drug synthesis and in material chemistry. A typical strategy for the pyrrolic ring formation is centered on the Paal−Knorr reaction, where 1,4-dicarbonyl compounds react with amines giving Nsubstituted pyrrole derivatives. Often, the main problem of this approach is the availability of the appropriate carbonyl compounds. Here, we report a sustainable synthesis of N-substituted pyrrole carboxylic acid derivatives by the reaction of primary amines and 3hydroxy-2-pyrones. These last compounds can easily be prepared using renewable sources and show the property to be masked 1,4-dicarbonyl compounds that are able to react efficiently with amines to form substituted pyrrolic rings. The reactions can be performed under sustainable conditions without solvents at 50−75 °C or in basic water− methanol solutions at room temperature, obtaining symmetric and asymmetric pyrroles from good to high yields. Moreover, dihydropyrrolepyrazinone derivatives can easily be prepared in high yields by the reaction of 3-hydroxy-2-pyrones and ethylenediamine.

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“…Thus, while simple 2HPs are difficult to synthesize as pure and isolated compounds, many of their benzo derivatives (i.e., 2 H -chromenes) constitute stable molecules, with a broad spectrum of biological activities and a widespread representation in the higher plants (Figure 1). Because the chemistry and reactivity of 2 H -chromenes have been already previously revised [1,10,11,12,13,14,15], they will not be included in this review. Instead, we will focus on the recent advances on accessing 2HPs, either as simple and stable monocyclic structures or as part of fused polycyclic structures, excluding the 2 H -chromene system.…”

Section: Introductionmentioning

confidence: 99%