Recent Synthetic Approaches to 1<i>H</i>- and 2<i>H</i>-Indazoles. A Review

Cankařová, Naděžda; Hlaváč, Jan; Krchňák, Viktor

doi:10.1080/00304948.2010.513898

Cited by 25 publications

(9 citation statements)

References 54 publications

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“…Indazoles are a useful class of N‐heteroaromatic compounds because they are crucial structural motifs of various biologically active compounds, particularly, bioisosteres for indoles and benzimidazoles . A large number of 2 H ‐indazole derivatives have been demonstrated for use as important biologically active compounds,– such as niraparib (PARP inhibitor) and liver X receptor agonist, in addition to fluorescent agents for cellular imaging in the field of chemical biology (Figure ) . Because of the high utility of N‐substituted indazoles, much attention has been devoted to establish novel and efficient strategies for their preparation.…”

Section: Figurementioning

confidence: 99%

Room‐Temperature, Metal‐Free, and One‐Pot Preparation of 2H‐Indazoles through a Mills Reaction and Cyclization Sequence

Kondo

Takizawa

Jiang

et al. 2019

Chemistry A European J

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The Mills reaction and cyclizationo fr eadily available 2-aminobenzyla lcohols and nitrosobenzenes using thionyl bromidep rovided 2H-indazoles in up to 88 %y ields. In the metal-free process, acetic acid played a crucial role for the both Mills reactiona nd cyclization. A brominated 2H-indazole could also be obtained through the one-pot sequence.Indazoles are au seful class of N-heteroaromatic compounds because they are crucial structural motifs of various biologically active compounds, [1] particularly,b ioisosteres for indoles and benzimidazoles. [1e] Al arge number of 2H-indazole derivatives have been demonstratedf or use as important biologically active compounds, [1c-h] such as niraparib (PARP inhibitor) [2] and liver Xr eceptor agonist, [3] in addition to fluorescent agents for cellular imaging in the field of chemical biology (Figure 1). [4] Because of the high utility of N-substituted indazoles, much attention has been devoted to establish novel and efficient strategies for their preparation. However,N -functionalization of indazoles often results in am ixture of 1H-a nd 2H-indazoles because the latter is thermodynamically disfavored in comparison with the former (energy difference between them is 2.3 kcal mol À1 ). [1e, 5, 6] Therefore, regioselective construction of the 2H-indazole skeleton remains ac hallenging task in organic synthesis. [4a, 7] Recently,t here have been af ew remarkable reports on the one-pot syntheses of 2H-indazoles. The synthesis involves a copper-catalyzedt hree-component reaction (Scheme 1a), [7a,b] Chem. Eur.

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Section: Figurementioning

confidence: 99%

Room‐Temperature, Metal‐Free, and One‐Pot Preparation of 2H‐Indazoles through a Mills Reaction and Cyclization Sequence

Kondo

Takizawa

Jiang

et al. 2019

Chemistry A European J

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“…Indazole is an organic heterocyclic compound called isoindazole or benzo[c]pyrazole, 1,2benzodiazole [1]. The discovery of indazolering was invented by Emil Fisher calling them fused benzene and pyrazole ring [2][3].…”

Section: Introductionmentioning

confidence: 99%

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Gaikwad

Kamble³

2022

J. Med. Chem. Sci.

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This research study discusses the silico design, synthesis, and biological evaluation of novel effective phenyl, indole, 3,4-dimethyl substituted 4,5,6,7tetrahydro-1H-indazole derivatives. The novel multi-substituted indazole derivatives (5A-5J) was synthesized from the treatment of hydrazine hydrates in MeOH/H+ with multi substituted clohexanone derivatives (4a-4j). The final scaffold was characterized with the help of spectroscopic data such asIR, 1H NMR, 13C NMR, and mass spectra. The compound 5A, 5D, and 5F shows excellent antibacterial activity and the compounds 5B, 5C, 5H 5I and 5J exhibited moderate antibacterial activity against the S. aureus, Bacillus subtilis and E.Coli. Finally, the molecular docking studies showes that the compound 5D and 5F scaffolds display excellent bonding mode of interactions with the active site of DNA gyrase 1KZN enzyme.

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“…Finally, syntheses promoted by palladium- [18] and rhodium-based [19] catalysts have also furnished these targets. A full listing of methods to prepare 1 H -indazoles, with and without the N1 aryl group, have been cataloged in three published reviews [20,21,22]. …”

Section: Introductionmentioning

confidence: 99%

Syntheses of 1-Aryl-5-nitro-1H-indazoles and a General One-Pot Route to 1-Aryl-1H-indazoles

2018

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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 series (73–96%), while the benzaldehyde series (63–73%) required a step-wise addition of reagents. A general one-pot protocol for 1-aryl-1H-indazole formation without the limiting substitution patterns required for the SNAr cyclization has also been achieved in 62–78% yields. A selection of 1-aryl-1H-indazoles was prepared in high yield by a procedure that requires only a single laboratory operation.

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Recent Synthetic Approaches to 1H- and 2H-Indazoles. A Review

Cited by 25 publications

References 54 publications

Room‐Temperature, Metal‐Free, and One‐Pot Preparation of 2H‐Indazoles through a Mills Reaction and Cyclization Sequence

Room‐Temperature, Metal‐Free, and One‐Pot Preparation of 2H‐Indazoles through a Mills Reaction and Cyclization Sequence

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Syntheses of 1-Aryl-5-nitro-1H-indazoles and a General One-Pot Route to 1-Aryl-1H-indazoles

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