An Overview of the Synthesis of 3,4-Fused Pyrrolocoumarins of Biological Interest

3,4-Fused pyrrolocoumarins, synthetically prepared or naturally occurring, possess interesting biological properties. In this review, the synthetic strategies for the synthesis of the title compounds are presented along with their biological activities. Two routes are followed for that synthesis. In one, the pyrrole ring is formed from coumarin derivatives, such as aminocoumarins or other coumarins. In the other approach, the pyranone moiety is built from an existing pyrrole derivative or through the simultaneous formation of coumarin and pyrrole frameworks. The above syntheses are achieved via 1,3-dipolar cycloaddition reactions, Michael reaction, aza-Claisen rearrangement reactions, multi-component reactions (MCR), as well as metal-catalyzed reactions. Pyrrolocoumarins present cytotoxic, antifungal, antibacterial, α-glucosidase inhibition, antioxidant, lipoxygenase (LOX) inhibition, and fluorescent activities, as well as benzodiazepine receptor ability.

AlCl3-catalyzed chemoselective cascade reactions of 4-anilinocoumarins with 2-furylcarbinols: access to densely functionalized chromeno[4,3-b]pyrrol-4(1H)-one derivatives

An unprecedented protocol has been developed for the preparation of highly functionalized chromeno[4,3-b]pyrrol-4(1H)-ones, which are not only valuable architectures of many biologically active molecules but also key building blocks for rich photophysical properties. The transformation proceeded through chemoselective intermolecular α-carbon nucleophilic attacking/ring-opening/Michael addition/deprotonation aromatization processes from 4-aminocoumarins and 2-furylcarbinols.

Recent Advances in Organic Synthesis of 3-Amino- or 4-Aminocoumarins

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Coumarin is a privileged scaffold that contains the unique 2H-chromen-2-one motif, and its derivatives are widely distributed in nature, especially in plants. In recent years, due to their diverse pharmacological activities and remarkable photochemical properties, they have attracted significant attention from scientists, which has also prompted the research on the synthesis approaches and the availability of substrates for these compounds. This article is a brief description of the methods for the synthesis of various coumarin derivatives via two- or multi-component reactions involving 3-amino or 4-aminocoumarin reported during 2015-2021. This review may help expand the development of various analogues with coumarin as the basic unit.

Alkynoates as Versatile and Powerful Chemical Tools for the Rapid Assembly of Diverse Heterocycles under Transition-Metal Catalysis: Recent Developments and Challenges

Heterocycles, heteroaromatics and spirocyclic entities are ubiquitous components of a wide plethora of synthetic drugs, biologically active natural products, marketed pharmaceuticals and agrochemical targets. Recognizing their high proportion in drugs and rich pharmacological potential, these invaluable structural motifs have garnered significant interest, thus enabling the development of efficient catalytic methodologies providing access to architecturally complex and diverse molecules with high atom-economy and low cost. These chemical processes not only allow the formation of diverse heterocycles but also utilize a range of flexible and easily accessible building units in a single operation to discover diversity-oriented synthetic approaches. Alkynoates are significantly important, diverse and powerful building blocks in organic chemistry due to their unique and inherent properties such as the electronic bias on carbon-carbon triple bonds posed by electron-withdrawing groups or the metallic coordination site provided by carbonyl groups. The present review highlights the comprehensive picture of the utility of alkynoates (2007-2019) for the synthesis of various heterocycles (> 50 types) using transition-metal catalysts (Ru, Rh, Pd, Ir, Ag, Au, Pt, Cu, Mn, Fe) in various forms. The valuable function of versatile alkynoates (bearing multifunctional groups) as simple and useful starting materials is explored, thus cyclizing with an array of coupling partners to deliver a broad range of oxygen-, nitrogen-, sulfur-containing heterocycles alongside fused-, and spiro-heterocyclic compounds. In addition, these examples will also focus the scope and reaction limitations, as well as mechanistic investigations into the synthesis of these heterocycles. The biological significance will also be discussed, citing relevant examples of drug molecules highlighting each class of heterocycles. This review summarizes the recent developments in the synthetic methods for the synthesis of various heterocycles using alkynoates as readily available starting materials under transition-metal catalysis.

Diverse synthesis of pyrrolo/indolo[3,2-c]coumarins as isolamellarin-A scaffolds: a brief update

This review presents a different synthetic approach of pyrrolo/indolo[3,2-c]coumarins via classical reactions including metal-catalyzed and green reaction protocols.

A decennary update on applications of metal nanoparticles (MNPs) in the synthesis of nitrogen- and oxygen-containing heterocyclic scaffolds

Heterocycles have been found to be of much importance as several nitrogen- and oxygen-containing heterocycle compounds exist amongst the various USFDA-approved drugs. Because of the advancement of nanotechnology, nanocatalysis has found abundant applications in the synthesis of heterocyclic compounds. Numerous nanoparticles (NPs) have been utilized for several organic transformations, which led us to make dedicated efforts for the complete coverage of applications of metal nanoparticles (MNPs) in the synthesis of heterocyclic scaffolds reported from 2010 to 2019. Our emphasize during the coverage of catalyzed reactions of the various MNPs such as Ag, Au, Co, Cu, Fe, Ni, Pd, Pt, Rh, Ru, Si, Ti, and Zn has not only been on nanoparticles catalyzed synthetic transformations for the synthesis of heterocyclic scaffolds, but also provide an inherent framework for the reader to select a suitable catalytic system of interest for the synthesis of desired heterocyclic scaffold.

Post-Ugi Cascade Transformations for Accessing Diverse Chromenopyrrole Collections

Employing a build/couple/pair strategy, a serendipitous one-pot protocol for the diastereoselective construction of diverse collections of chromenopyrroles is described. This methodology features an unprecedented five-step cascade including azomethine ylide generation followed by in situ intramolecular [3 + 2]-cycloaddition. Furthermore, this protocol was extended to access enantiopure chromenopyrroles using amino acids as chiral auxiliary. Moreover, postpairing reactions were employed to increase the diversity and complexity of our pilot compound collections.

Copper ferrite nanoparticle modified starch as a highly recoverable catalyst for room temperature click chemistry: multicomponent synthesis of 1,2,3-triazoles in water

Highly water dispersible CuFe₂O₄@Starch catalyzed click reaction.

Synthesis of Novel 5,6-Disubstituted Pyrrolo [2,3-d]Pyrimidine-2,4-Diones Via One-Pot Three-Component Reactions

A simple and novel method for the synthesis of 5,6-disubstituted pyrrolo[2,3-d]pyrimidine-2,4-diones has been reported using arylglyoxal-based three-component reactions. Under microwave heating conditions, arylglyoxal, 6-amino uracil, or its derivatives reacts with various thiols in acetic acid medium to provide a series of pyrrolo[2,3-d]pyrimidine-2,4-diones (4) having a thioether and an aryl ring in 5 and 6 positions, respectively. On the other hand reaction of arylglyoxal, amino uracil and malononitrile in place of thiols, provided corresponding 5,6-disubstituted pyrrolo[2,3-d]pyrimidine-2,4-diones (5) with selectively converting one of the -CN to -CONH₂ group both in conventional (method A) and microwave heating conditions (method B). This methodology is a simple and efficient protocol for the synthesis of diverse 5,6-disubstituted pyrrolo[2,3-d]pyrimidine-2,4-diones from the readily available starting materials in good yields.

Facile and eco-friendly synthesis of chromeno[4,3-b]pyrrol-4(1H)-one derivatives applying magnetically recoverable nano crystalline CuFe2O4 involving a domino three-component reaction in aqueous media

Nanocrystalline CuFe₂O₄ catalyzed one pot three component synthesis of chromeno[4,3-b]pyrrol-4(1H)-one derivatives has been achieved in aqueous media.

Magnetically separable CuFe2O4/reduced graphene oxide nanocomposites: as a highly active catalyst for solvent free oxidative coupling of amines to imines

Solvent free aerobic oxidative coupling of amines to imines in presence of CuFe₂O₄/RGO nanocomposites.

Coumarin heterocyclic derivatives: chemical synthesis and biological activity

This review highlights the broad range of science that has arisen from the synthesis of coumarin-linked and fused heterocycle derivatives. Specific topics include their synthesis and biological activity.

Nickel ferrite nanoparticles: an efficient and reusable nanocatalyst for a neat, one-pot and four-component synthesis of pyrroles

We applied magnetic NiFe₂O₄ as a recoverable catalyst in the multicomponent reaction of substituted pyrroles. Magnetic NiFe₂O₄ could be recovered from the reaction easily with an external magnet and reused nine times without significant activity loss. The yields are high.

Heterogeneous Fe-MIL-101 catalysts for efficient one-pot four-component coupling synthesis of highly substituted pyrroles

Fe-MIL-101 as efficient heterogeneous catalysts for four-component coupling synthesis of highly substituted pyrroles.

Synthesis of heterocycles and fused heterocycles catalyzed by nanomaterials

The application of nanomaterials as heterogeneous catalyst for the synthesis of different heterocyclic systems is reviewed.

Pyrrole: a resourceful small molecule in key medicinal hetero-aromatics

Pyrrole is widely known as a biologically active scaffold which possesses a diverse nature of activities.

A facile and efficient synthesis of functionalized 4-oxo-2-(phenylimino)thiazolidin-5-ylideneacetate derivatives via a CuFe2O4 magnetic nanoparticles catalyzed regioselective pathway

Nano-CuFe₂O₄ spinel has been found to exhibit strong catalytic activity in the cascade reaction involving 1,4-addition and intramolecular electrophilic cyclization in a perfectly regiocontrolled manner and a series of functionalized 4-oxo-2-(phenylimino)thiazolidin-5-ylideneacetate derivatives were generated successfully.

Exploration of uracils: pot and step economic production of pyridine core containing templates by multicomponent aza-Diels–Alder reaction

Substituted pyrido[2,3-d]pyrimidines can be obtained with good yields via a multicomponent aza-Diels–Alder reaction from easily available starting materials. The diene behaviour of different uracil derivatives was also elaborately investigated to synthesize desired products.