The Reaction of Meldrum's Acid with Aldehydes and Phloroglucinol: A Synthesis of Dihydrocoumarins<sup>1</sup>

Nair, Vipin A.

doi:10.1080/00397918708075747

Cited by 31 publications

(12 citation statements)

References 8 publications

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“…Finally, it has also been reported that phenol derivatives can be used as nucleophiles in the tandem Knoevenagel condensation/Michael addition. In this way, the methylene derivatives resulting from the reactions between aldehydes and Meldrum’s acid have been intercepted with phloroglucinol, offering a convenient route to certain dihydrocoumarins (Scheme ) 181…”

Section: Mcrs Based On the Knoevenagel Reactionmentioning

confidence: 99%

Utilisation of 1,3‐Dicarbonyl Derivatives in Multicomponent Reactions

2004

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Although isocyanide‐based multicomponent reactions (MCRs), introduced in 1921 by Passerini, largely predominate nowadays in the construction of widely diverse heterocycles, one of the first substrate classes involved in a MCR was that of 1,3‐dicarbonyl derivatives, with Hantzsch’s dihydropyridine synthesis appearing as early as 1882. The aim of this microreview is to present an overview of the great synthetic potential of MCRs involving the specific reactivity of easily accessible 1,3‐dicarbonyl derivatives and to stress their more recent utilisation for the development of new and useful methodologies valuable for the selective construction of highly functionalised small organic molecules of high synthetic and biological value. After a short general introduction, we present chronologically the different methodologies developed on the bases of the reactivity of 1,3‐dicarbonyl systems towards many other substrates involved in a variety of synthetic pathways, including Knoevenagel condensations, Michael and Mannich reactions, cyclodehydrations, electrocyclisations, cycloadditions and metal‐promoted transformations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

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Section: Mcrs Based On the Knoevenagel Reactionmentioning

confidence: 99%

Utilisation of 1,3‐Dicarbonyl Derivatives in Multicomponent Reactions

2004

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“…The crude product was subjected to column chromatography (silica, Et 2 O-CH 2 Cl 2 , 1:1) to provide 15 (1.7 g, 80%) as a white solid; mp 206-207°C (lit. 25…”

Section: 7-dihydroxy-4-phenyl-chroman-2-one (15)mentioning

confidence: 99%

An Efficient Synthesis of Neoflavonoid Antioxidants Based on Montmorillonite K-10 Catalysis

Lee¹,

Tseng²,

Lee³

2001

Synthesis

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A new approach to synthesis of neoflavonoids, based on a high yielding Montmorillonite K-10 catalyzed lactone ring forming cyclization process, is described. The utility of this methodology is exemplified by its employment in the preparation of the substituted 4-phenylneoflavonoids 1-8. The free radical scavenging properties of these substances were evaluated. The neoflavonoids 1 and 5, which mimic esculetin-type antioxidants, were observed to quench hydrazyl free radicals.As part of a recent search 1 to prepare new biologically active substances, we were attracted to the coumarin family whose members are widely distributed in biologically important natural products and pharmaceutical agents. 2 Coumarins exist in free or glycoside-conjugated forms in a wide variety of plants. 3 Indirect analgesic effects (abolition of oedema and inflammation) of coumarin in rabbit have been observed. 4 Coumarin and 7-hydroxycoumarin also inhibit the biosynthesis of prostaglandins and leucotrienes to about the same degree as acetylsalicylic acid. 5 Moreover, this substance has anti-oedematous, lymphokinetic and haemorheological properties. 6 Naturally occurring neoflavonoid glycosides are known to serve as inhibitors of energy transfer in spinach chloroplasts. 7 Inspite of these effects, Zobel and Brown 8 have concluded that the biologcal roles of coumarins are not well understood.In our previous studies, we have demonstrated that esculetin (6,7-dihydroxycoumarin) possesses potent antioxidant and antitumor promotion properties. 9 The data indicate that this compound induces apoptosis in human leukemia cells by increasing cytosolic translocation of cytochrome c and activating the cysteine protease 32 kDa proenzyme (CPP32). 4-Phenylcoumarins are also of synthetic interest owing to the fact that this ring system is present in a number of naturally occurring compounds, such as serratin, 10a dalbergin, 10b-10d calophyllolide, 10e calomelanols B and C 11 and vismiaguianones D and E. 3dAs a consequence of the biological and structural interest in these substances, we initiated a study aimed at developing a general and high yielding method to prepare coumarins. The commercial availability of cinnamic acids and phloroglucinol prompted us to probe a route to the neoflavonoids, which is based on an esterification-cyclization sequence. It is known that regioselective esterification of the a,b-unsaturated carboxylic acids with polyphenols often is problematic due to competition between cyclization by Friedel-Crafts acylation and Fries rearrangement of the initially formed ester intermediate. 12 Although the synthesis of some coumarins has been successfully approached by using this strategy, 13 harsh condition and high substrate concentrations are commonly required. In addition, Shamsuddin has reported a one-pot procedure for the synthesis of 4-phenylcoumarins. 14 However, the scope of this process appears to be limited. For instance, by following Shamsuddin's procedure, we were unable to efficiently prepare 5,7-dihydroxy-4-phenylcoumarin f...

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“…5-Methylene Meldrum's acids, which are easily prepared by a variety of methods 1 (in particular by the Knoevenagel reaction of (1) with carbonyl compounds), undergo conjugate additions with various nucleophiles, such as hydride (eq 8), 9 organometallic reagents (eq 9), 10 and phenols (eq 10). 11 Polyacylated alkenes are susceptible to conjugate addition of enolates, leading to a variety of products (eq 11). 12 Analogously, homoconjugate addition of nucleophiles to spiro-cyclopropyl derivatives takes place resulting in cyclopropyl ring opening (eq 12 Cycloaddition.…”

Section: Ring Opening Reactions Initiated By Nucleophilesmentioning

confidence: 99%

2,2-Dimethyl-1,3-dioxane-4,6-dione

Yonemitsu

Hirao

2001

Encyclopedia of Reagents for Organic Synthesis

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The Reaction of Meldrum's Acid with Aldehydes and Phloroglucinol: A Synthesis of Dihydrocoumarins¹

Cited by 31 publications

References 8 publications

Utilisation of 1,3‐Dicarbonyl Derivatives in Multicomponent Reactions

Utilisation of 1,3‐Dicarbonyl Derivatives in Multicomponent Reactions

An Efficient Synthesis of Neoflavonoid Antioxidants Based on Montmorillonite K-10 Catalysis

2,2-Dimethyl-1,3-dioxane-4,6-dione

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The Reaction of Meldrum's Acid with Aldehydes and Phloroglucinol: A Synthesis of Dihydrocoumarins1

Cited by 31 publications

References 8 publications

Utilisation of 1,3‐Dicarbonyl Derivatives in Multicomponent Reactions

Utilisation of 1,3‐Dicarbonyl Derivatives in Multicomponent Reactions

An Efficient Synthesis of Neoflavonoid Antioxidants Based on Montmorillonite K-10 Catalysis

2,2-Dimethyl-1,3-dioxane-4,6-dione

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The Reaction of Meldrum's Acid with Aldehydes and Phloroglucinol: A Synthesis of Dihydrocoumarins¹