Efficient multicomponent strategy to pentacyclic pyrazole-fused naphtho[1,8-fg]isoquinolines through cleavage of two carbon-carbon bonds

Regioselective Synthesis of Cycloalkane-fused Pyrazolo[4,3-e]pyridines through Tandem Reaction of 5-aminopyrazoles, Cyclic Ketones and Electron-rich Olefins

BACKGROUND

Pyrazolopyridines are interesting fused heterocyclic pharmacophores that combine pyrazole and pyridine; two privileged nuclei extensively studied and with a wide range of applications. They can be obtained by a broad variety of synthetic methods among which multicomponent reactions have gained importance, especially from 5-aminopyrazoles and dielectrophilic reagents. However, the search for new approaches more in tune with sustainable chemistry and the use of unconventional heating in three-component synthesis are open and highly relevant study fields.

METHODS

A novel, practical and efficient three-component synthesis of cycloalkane-fused pyrazolo[ 4,3-e]pyridines was developed through a tandem reaction of 5-aminopyrazoles, cyclic ketones and electron-rich olefins, using microwave induction in perfluorinated solvent and iodine as catalyst.

RESULTS

The microwave-induced three-component approach applied in this work promoted the construction of 10 new pyrazolopyridines with high speed and excellent control of regioselectivity, favoring the linear product with good yields; where the versatility of electron-rich olefins in iodine-catalyzed cascade heterocyclizations, granted the additional benefit of easy isolation and the possibility to reuse the fluorous phase.

CONCLUSION

Although pyrazolopyridines have been synthetically explored because of their structural and biological properties, most of the reported synthetic methods use common or even toxic organic solvents and conventional heating or multi-step processes. In contrast, this study applied a multicomponent methodology in a single step by microwave induction and with the versatility provided in this case by the use of perfluorinated solvent, which allowed easy isolation of the final product and recovery of the fluorous phase.

A close look into the biological and synthetic aspects of fused pyrazole derivatives

The fusion of pyrazole scaffold with other skeletons creates a class of attractive molecules, demonstrating significant biological and chemical potentiality in the development of medicinal chemistry. Over the past few decades, numerous biologically active molecules featuring fused pyrazole moieties have been excavated and synthesized, some of which represented by sildenafil have been marketed as drugs, and the biological importance together with chemical synthesis strategies of fused pyrazole compounds, including structural modification based on lead compounds, have been steadily progressing. In this review, we focused our attention on the biological importance of fused pyrazoles and highlighted recent progress in the synthesis of this framework over the past 10 years. What' s more, the limitations, challenges, and future prospects were proposed, wishing to provide references for the development of pyrazole fused frameworks in the field of medicinal chemistry. Contents.

Selective access to dipyrazolo-fused pyridines via formal [3 + 2 + 1] heteroannulation of methyl ketones with pyrazol-5-amines

A fascinating new form of the Hantzsch reaction with methyl ketones and pyrazol-5-amines for the selective synthesis of dipyrazolo-fused pyridines has been discovered.

Recent synthetic and medicinal perspectives of dihydropyrimidinones: A review

Dihydropyrimidines are the most important heterocyclic ring systems which play an important role in the synthesis of DNA and RNA. Synthetically they were synthesized using Multi-component reactions like Biginelli reaction and Hantzschdihydropyridine. In the past decades, such Biginelli type dihydropyrimidones have received a considerable amount of attention due to the interesting pharmacological properties associated with this heterocyclic scaffold. In this review, we highlight recent developments in this area, with a focus on the DHPMs, recently developed as anti-inflammatory, anti-HIV, anti-tubercular, antifungal anticancer, antibacterial, antifilarial, antihyperglycemic, antihypertensive, analgesic, anti-convulsant, antioxidant, anti-TRPA1, anti-SARS, and anti-cancer activity and α_1a binding affinity.

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This review is focused on synthetic prospective of dihydropyrimidinones.

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This review is also focused on medicinal prospective of dihydropyrimidinones.

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It includes structure-activity relationship study of different activities.

Three-component synthesis of new o-hydroxyphenyl-substituted pyrazolo[3,4-b]pyridines promoted by FeCl3

An efficient three-component synthesis of o-hydroxyphenyl-substituted pyrazolo[3,4-b]pyridines from substituted salicylic aldehydes, β-keto esters and 5-aminopyrazoles in the presence of FeCl3 is presented. Newly synthesized compounds were fully characterized by means of 1H NMR, 13C NMR, IR, HRMS and elemental analysis.

ZrCl4-Catalysed Synthesis of New 4-(2-hydroxyphenyl)Pyrazolo[3,4-b]Pyridine Derivatives

In the presence of a catalytic amount of zirconium(IV) chloride, an efficient synthesis of new 4-(2-hydroxyphenyl)pyrazolo[3,4-b]pyridines has been developed by the reaction 2-hydroxychalcones with 3-methyl-1-phenyl-1H-pyrazol-5-amine in refluxing ethanol. All these novel compounds have been characterised by 1H NMR, 13C NMR, HRMS, IR spectra and X-ray crystallographic analysis.

Palladium mediated regioselective intramolecular Heck reaction: synthesis of 1,3,4-trisubstituted pyrazolo[3,4-b]pyridines, 3H-pyrazolo[3,4-c]isoquinolines and 3H-pyrazolo[4,3-f][1,7]naphthyridines

A new approach for the synthesis of 1,3,4-trisubstituted pyrazolo[3,4-b]pyridines, 3H-pyrazolo[3,4-c]isoquinolines and 3H-pyrazolo[4,3-f][1,7]naphthyridines via an intramolecular Heck reaction is described.

Selective synthesis of polyfunctionalized pyrido[2,3-b]indoles by multicomponent domino reactions

A series of novel polyfunctionalized pyrido[2,3-b]indoles were synthesized by three- or four-component domino reactions under microwave irradiation. This protocol has the advantages of readily available starting materials, short reaction times, high yields, easy workup, and high chemo- and regioselectivities.

I2/O2-promoted domino reactions of isatins or 3-hydroxyindolin-2-one derivatives with enaminones

I2-promoted domino reactions of isatins or 3-hydroxyindolin-2-one derivatives with enaminones under O2 conditions have been established. The reactions of isatins with enaminones afforded functionalized tetracyclic pyrrolo[2,3,4-kl]acridine derivatives in moderate to good yields through domino cyclization and C-H oxidation. The reactions of 3-hydroxyindolin-2-one derivatives with enaminones proceeded well to give functionalized pyrrolo[2,3,4-kl]acridine derivatives via tandem ring-opening/recyclization/methyl migration sequences with two C-C bonds cleaved.