Syntheses of chromenes and chromanes <i>via </i><i>o</i>‐quinone methide intermediates

Ferreira, Sabrina Baptista; Silva, Fernando de Carvalho da; Pinto, Ângelo C.; Gonzaga, Daniel T. G.; Ferreira, Vı́tor F.

doi:10.1002/jhet.232

Cited by 125 publications

(42 citation statements)

References 201 publications

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“…These results are consistent with those previously described in the literature, [39][40][41][42][43] which indicate that the para-isomer always forms in greater proportion due to the greater reactivity of the leading isomer of o-quinone methide. In reactions using diphenyl urea, the ratio is reversed (1:2) for R = Ph, indicating that the steric effects around the o-quinone methide intermediate are driving the selectivity of the reactions.…”

Section: Resultssupporting

confidence: 93%

Synthesis of New Xanthenes Based on Lawsone and Coumarin via a Tandem Three‑Component Reaction

Cardoso¹,

Forezi²,

Cavalcante³

et al. 2017

J. Braz. Chem. Soc.

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The synthesis of several new xanthenes based on the 1,3-dicarbonyl scaffolds lawsone and coumarin was developed using tandem three-component reactions involving the reagents ortho-hydroxybenzaldehyde, as bifunctional reagent, and an appropriate thiol. These reactions generated two series of para-and ortho-naphthoxanthenes that are structurally related to α-and β-pyranaphthoquinones and one series of coumarin-xanthene derivatives.Keywords: 2-hydroxy-1,4-naphthoquinone, coumarin, multi-component reactions, organocatalysis, ortho-quinone methide IntroductionXanthenes are a class of heterocyclic compounds that are extensively found in natural products and have many biological applications and several applications in materials science. [1][2][3] Xanthenes are prepared by several synthetic methods and structurally possess carbocyclic or heterocyclic substituents fused to a central pyran ring. In general, the most commonly used methods for their preparation involve a cycloaddition reaction of a 1,3-dicarbonyl compound with aldehydes to form an adduct, a reactive α,β-unsaturated intermediate, which reacts with an appropriate nucleophile in the second step. [4][5][6] Lawsone (1) and 4-hydroxycoumarin (6) are two 1,3-dicarbonyl compounds that have been extensively used by synthetic organic chemists because of their peculiar chemical structures and their relationships with biologically important natural products. 7 Indeed, these natural products have a large variety of biological activity that has been studied in recent decades and stimulated the synthesis of a large number of synthetic analogues. [8][9][10][11] Naphthoquinones play vital roles in several biological processes and are considered to be of great importance in medicinal chemistry. Naphthoquinones are often associated with various biological activities, including anticancer, antibacterial, antimalarial, trypanocidal, tuberculostatic and fungicidal activities. 12 Some natural coumarins are found as secondary metabolites from plants, bacteria and fungi. 13 This family of compounds presents a wide variety of biological activities, including anti-inflammatory, antibacterial, antifungal, antiviral and anticancer. 14,15 In Figure 1, we highlight the following important natural and synthetic naphthoquinones that match this profile: lawsone (1), β-lapachone (2), α-lapachone (3), urdamycinone B (4), estreptonigrin (5), 4-hydroxycoumarin (6), calanolide A (7) and osthole (8). [16][17][18][19] Because of the importance of these naphthoquinones and coumarins, the search for new, simple and efficient methods of preparation of structurally related compounds remains of great interest.Tandem multi-component reactions (MCR) are convergent syntheses that begin with three or more reactants and, preferably, end with only one formed product that contains all of the starting atoms. 20 Usually, these types of reactions have a high atom economy and a high possibility of diversifying the structures of the final products. MCRs are important in industrial applications 21 and the devel...

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Section: Resultssupporting

confidence: 93%

Synthesis of New Xanthenes Based on Lawsone and Coumarin via a Tandem Three‑Component Reaction

Cardoso¹,

Forezi²,

Cavalcante³

et al. 2017

J. Braz. Chem. Soc.

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“…67 A proposed mechanism for the quinone methide formation in a protic media is shown in Scheme 4. After the nucleophilic attack of lawsone to the protonated aldehyde 12, followed by water elimination, the quinone methides 16 and 17 may be formed by protonation/deprotonation in an acid-base equilibrium.…”

Section: Figure 2 1 H-1 H Correlation Spectroscopy Of 7a In Cdclmentioning

confidence: 99%

Insight into and Computational Studies of the Selective Synthesis of 6H-Dibenzo[b,h]xanthenes

et al. 2016

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Starting from 2-hydroxy-1,4-naphthoquinone (lawsone), we synthesized eight new 6H-dibenzo[b,h]xanthene derivatives selectively under solvent-free conditions. Spectroscopic investigations confirmed that only the isomer 6H-dibenzo[b,h]xanthene was obtained in all eight cases. Computational studies provide a rationalization for the selective appearance of these isomers having as an intermediate an addition product.

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“…6 We sought to develop a collection of enantioselective catalytic boronate addition reactions to ortho -quinone methides and related intermediates. 7 Inspiration for this target class of reactions is derived from the numerous bioactive natural products and drugs, only a few depicted in Scheme 1, all of which can be made via this type of enantioselective addition (Eq. 1).…”

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confidence: 99%

Enantioselective Addition of Boronates to o-Quinone Methides Catalyzed by Chiral Biphenols

2012

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Syntheses of chromenes and chromanes via o‐quinone methide intermediates

Cited by 125 publications

References 201 publications

Synthesis of New Xanthenes Based on Lawsone and Coumarin via a Tandem Three‑Component Reaction

Synthesis of New Xanthenes Based on Lawsone and Coumarin via a Tandem Three‑Component Reaction

Insight into and Computational Studies of the Selective Synthesis of 6H-Dibenzo[b,h]xanthenes

Enantioselective Addition of Boronates to o-Quinone Methides Catalyzed by Chiral Biphenols

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