Microwave-assisted synthesis of 1-aryl-1H-indazoles via one-pot two-step Cu-catalyzed intramolecular N-arylation of arylhydrazones
摘要:
A highly efficient one-pot two-step microwave procedure was developed for the synthesis of 1-aryl-1H-indazoles. Microwave heating of 2-halobenzaldehydes or 2-haloacetophenones with phenylhydrazines at 160 degrees C for 10 min quantitatively yielded the arylhydrazones, which were further cyclized to give 1-aryl-1H-indazoles via CuI/diamine-catalyzed N-arylation under microwave heating (160 degrees C, 10min). Good to excellent yields were observed for 2-iodo, 2-bromo, and 2-chloro benzaldehydes or acetophenones. (c) 2005 Elsevier Ltd. All rights reserved.
A copper-catalyzed direct C–H chalcogenation of N-aryl-azaindoles with disulfides is described.
一种铜催化的直接C-H硫砜化反应,用于N-芳基-氮杂吲哚与二硫化物的反应。
Pyrazolo[3,4-<i>b</i>]pyridines: Syntheses, reactions, and nuclear magnetic resonance spectra
作者:Brian Maurice Lynch、Misbahul Ain Khan、Huk Chia Teo、Francisco Pedrotti
DOI:10.1139/v88-074
日期:1988.3.1
2-Chloro-3-formylpyridine (2-chloronicotinaldehyde) was obtained by reduction of 2-chloro-3-cyanopyridine by Raney nickel and formic acid (3 1); this intermediate is inaccessible by the above N-oxidation route (peroxyacid oxidation of 3-formylpyridine yields pyridine-N-oxide 3-carboxylic acid). In the synthesis of the parent 1 from 2-chloro-3-formylpyridine, the yield was prejudiced by the formation
An efficient route to substituted 1-aryl-1H-indazoles has been developed and optimized. The method involved the preparation of arylhydrazones from acetophenone or benzaldehyde substituted by fluorine at C2 and nitro at C5, followed by deprotonation and nucleophilic aromatic substitution (SNAr) ring closure in 45-90%. Modification of this procedure to a one-pot domino process was successful in the acetophenone
A general synthesis of 1‐aryl‐1‐H‐indazoles from o‐halogenated aryl aldehydes or ketones and aryl hydrazines was described. This protocol included an intermolecular condensation and a ligand‐free copper‐catalyzedintramolecular Ullmann‐type coupling reaction. This method was applied to a wide range of substrates to produce the indazole products in good yields.