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Relevant academic research and scientific papers

Gold modified zeolite: An efficient heterogeneous catalyst for n-arylation of indazole

We herein report N-arylation of indazole with aryl halides using gold modified zeolites (Au-zeolites) as an efficient catalytic system. Au-zeolites with three different gold loading were prepared by ion-exchange method and characterized by UV-visible diffuse reflectance spectroscopy (UV-DRS), transmission electron microscopy and energy-dispersive X-ray spectroscopy (TEM-EDX) and X-ray photoelectron spectroscopy (XPS). The Brunauer-Emmett-Teller (BET) and Langmuir surface areas of the prepared Au(5)-zeolite catalyst were found to be 644 and 929 m2g-1 respectively. Goldmodified zeolites performed as an efficient catalytic system for N-arylation of indazole using diverse aryl halides afforded N1 arylated products in appreciable yield under mild reaction conditions. The catalyst was reusable for at least five times with only a marginal loss of activity. This simple, effective and environmentally benign heterogeneous protocol provides a safer alternative to hazardous, corrosive and more polluting conventional catalysts.

Highly Efficient One-Pot Three Component Synthesis of 2H-Indazoles by Consecutive Condensation, C–N and N–N Bond Formations Using Cu/Aminoclay/Reduced Graphene Oxide Nanohybrid

A simple and straightforward one-pot three-component synthesis of 2H-indazoles through copper-catalyzed consecutive condensation, C–N and N–N bond formations of easily accessible starting materials under ligand-free conditions is described. In this protocol, treatment of substituted 2-bromobenzaldehydes, structurally diverse amines, and [bmim]N3 in the presence of Cu/aminoclay/reduced graphene oxide nanohybrid (Cu/AC/r-GO nanohybrid) as an efficient heterogeneous catalyst affords the corresponding 2H-indazoles in good to excellent yields. The influence of effective parameters on the efficient progress of the reaction was studied. The Cu/AC/r-GO nanohybrid is a stable and inexpensive catalyst that could be simply prepared, recovered, and reused for several reaction runs with no significant decrease in its reactivity.

Metal acetylacetonates covalently anchored onto amine functionalized silica/starch composite for the one-pot thioetherification and synthesis of 2H-indazoles

This paper reports a series of novel metal acetylacetonates covalently anchored onto amine functionalized silica/starch composite, prepared by the Schiff condensation of metal acetylacetonates [Co(acac)2, Cu(acac)2, Pd(acac)2, Ru(acac)3, Mn(acac)3, Co(acac)3] with organically modified 3-aminopropyl silica/starch composite. Different metal acetylacetonates have been chosen with a view to select the most active heterogeneous catalyst. Among various catalysts, covalently anchored Cu(acac)2 onto amine functionalized silica/starch composite [ASS-Cu(acac)2] was found to be the most active and recyclable catalyst for the one-pot thioetherification and one-pot three component synthesis of 2H-indazoles via consecutive C-N and N-N bond formations. All the catalysts were characterized by FTIR, TGA and AAS analysis and the most active catalyst, [ASS-Cu(acac)2] was further characterized by SEM and TEM. The catalyst could be recovered by simple filtration and reused with almost consistent activity for four consecutive runs.

A general and efficient approach to 2H-indazoles and 1H-pyrazoles through copper-catalyzed intramolecular N-N bond formation under mild conditions

A new efficient copper-catalyzed intramolecular amination reaction has been developed to readily synthesise a wide variety of multi-substituted 2H-indazole and 1H-pyrazole derivatives from easily accessible starting materials under mild conditions. A highly selective ligand for estrogen receptor β was prepared in three steps by employing this method. The Royal Society of Chemistry 2011.

Consecutive condensation, C-N and N-N bond formations: A copper-catalyzed one-pot three-component synthesis of 2 H -indazole

2H-Indazoles are synthesized using copper-catalyzed, one-pot, three-component reactions of 2-bromobenzaldehydes, primary amines, and sodium azide. A copper catalyst plays the key role in the formation of C-N and N-N bonds. This method has a broad substrate scope with a high tolerance for a variety of functional groups.

Synthesis of p-nitrophenylazoles by phase transfer catalysis without solvent

Several N-p-nitrophenylazoles have been synthesized by direct arylation of the corresponding azole with p-fluoronitrobenzene (FNB) using phase-transfer catalysis (PTC) without solvent.