93326-45-5Relevant academic research and scientific papers
Gold modified zeolite: An efficient heterogeneous catalyst for n-arylation of indazole
Emayavaramban,Kadirvelu,Dharmaraj
, p. 9093 - 9103 (2016/08/30)
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.
Synthesis of 1-aryl-1H-indazoles via palladium-catalyzed intramolecular amination of aryl halides
Lebedev, Artyom Y.,Khartulyari, Anton S.,Voskoboynikov, Alexander Z.
, p. 596 - 602 (2007/10/03)
(Chemical Equation Presented) Palladium-catalyzed cyclization of arylhydrazones of 2-bromoaldehydes and 2-bromoacetophenones to give 1-aryl-1H-indazoles has been studied in detail. The cyclization of arylhydrazone of 2-bromobenzaldehydes can be performed with good to high yields using Pd(dba)2 and chelating phosphines, of which the most effective are rac-BINAP, DPEphos, and dppf, in the presence of Cs2CO3 or K3PO4 as a base. Electron-rich, bulky ligands commonly employed for intermolecular amination such as PtBu3 and o-PhC6H4PtBu2 were shown to be ineffective for cyclization and to lead instead to extensive oligomerization and tarring. The method developed is applicable for preparation of a wide scope of indazoles bearing electron-donating or electron-withdrawing substituents, among them, unprotected carboxyl, as well as various indazole heteroanalogues. The cyclization of arylhydrazones of less reactive halides such as 2-chlorobenzaldehyde, as well as 2-bromoacetophenone and bromotetralone, has been achieved. The purity of the starting hydrazone has been shown to be a critical parameter, as various impurities inhibit the cyclization.
