Progress of the synthesis of condensed pyrazole derivatives (from 2010 to mid-2013).

This work was supported by the current Spanish Ministerio de Economia y Competitividad (CTQ2011-24151) and by the University of Alicante.

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Magnetite and Metal-Impregnated Magnetite Catalysts in Organic Synthesis: A Very Old Concept with New Promising Perspectives

5-Amino-pyrazoles have proven to be a class of fascinating and privileged organic tools for the construction of diverse heterocyclic or fused heterocyclic scaffolds. This review presents comprehensively the applications of 5-amino-pyrazoles as versatile synthetic building blocks in the synthesis of remarkable organic molecules with an emphasis on versatile functionalities. Following a brief introduction of synthesis methods, planning strategies to construct organic compounds, particularly diverse heterocyclic scaffolds, such as poly-substituted heterocyclic compounds and fused heterocyclic compounds via 5-amino-pyrazoles, have been summarized. Fused heterocycles are classified as bicyclic, tricyclic, tetracyclic, and spiro-fused pyrazole derivatives. These outstanding compounds synthesized via wide variety of approaches include conventional reactions, one-pot multi-component reactions, cyclocondensation, cascade/tandem protocols, and coupling reactions. 5-Amino-pyrazoles represent a class of promising functional reagents, similar to the biologically active compounds, highlighted with diverse applications especially in the field of pharmaceutics and medicinal chemistry. Notably, this critical review covers the articles published from 1981 to 2018.

5-Amino-pyrazoles: potent reagents in organic and medicinal synthesis

Unsupported nanoparticles are often less stable, and usually coagulation is unavoidable during the catalytic reactions. To generate stable nanoparticles with good activity, stabilizing the surface is required. Protection has been performed by the addition of polymers or long-chain alkyl surfactants with polar functional groups that attached to the nanoparticle surface via covalent or electrostatic interactions. Alternatively, nanoparticles have been immobilized or grafted onto inorganic supports to improve their stabilization and recycling ability. In this article, the green catalytic processes and recent advances in organic transformations catalyzed by magnetically retrievable catalysts are reviewed. Prior to this, methods for the synthesis of catalysts immobilized on magnetic nanoparticles are addressed briefly.

Recent advances in catalysts immobilized on magnetic nanoparticles

Magnetically separable Fe3O4 nanoparticles were used as an environmental friendly catalyst for the synthesis of mono- and bis-tetrahydro-4H-chromene and mono- and bis-1,4-dihydropyridine derivatives via three-component reactions of aromatic aldehydes and malononitrile with cyclic β-dicarbonyls or cyclic β-enaminoketones respectively. These reactions were carried out in EtOH and at reflux. Fe3O4 nanoparticles can be magnetically separated from the reaction mixture by a magnet and recycled without significant loss of catalytic activity.

Evaluation of magnetically recyclable nano-Fe3O4 as a green catalyst for the synthesis of mono- and bis-tetrahydro-4H-chromene and mono and bis 1,4-dihydropyridine derivatives

A multicomponent reaction for the synthesis of fused azo-linked pyrazolo[4,3-e]pyridines from 3-amino-5-methylpyrazole, indan-1,3-dione and synthesized azo-linked aldehydes using nano-Fe3O4 as an effective and reusable catalyst is reported. The present methodology offers several advantages, such as a simple procedure with an easy work-up, short reaction times, high yields, and the absence of any volatile and hazardous organic solvents.

Regioselective Synthesis of Fused Azo-linked Pyrazolo[4,3-e]pyridines Using Nano-Fe3O4

The reaction is conducted under environmentally benign conditions and has an easy work-up procedure.

Tamila Shafaati

Papers

Regioselective Synthesis of Fused Azo-linked Pyrazolo[4,3-e]pyridines Using Nano-Fe3O4

Regioselective Synthesis of Fused Azo-Linked Pyrazolo[4,3-e]pyridines Using Nano-Fe3O4.