Divergent Synthesis of 1H‐Indazoles and 1H‐Pyrazoles from Hydrazones via Iodine‐Mediated Intramolecular Aryl and sp3 C–H Amination

Wei, Wei; Wang, Zhen; Yang, Xikang; Yu, Wenquan; Chang, Junbiao

doi:10.1002/adsc.201700824

Cited by 34 publications

(7 citation statements)

References 45 publications

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“…Substituted aminohydrazones were easily prepared based on trifluoromethanesulfonic anhydride-mediated activation of tertiary amides 5 , and the addition of nucleophilic hydrazides ( Scheme 1 ). Chang et al [ 16 ] treated diaryl and tert -butyl aryl ketone hydrazones 8 with iodine in the presence of potassium iodide and sodium acetate obtaining 1 H -indazoles 9 via direct aryl C-H amination, as shown in Scheme 2 . The synthesis of 1 H -indazoles 11 from arylhydrazones 10 through direct aryl C-H amination using [bis-(trifluoroacetoxy)iodo]benzene (PIFA) as an oxidant was described by Zhang et al ( Scheme 3 ) [ 17 ].…”

Section: Synthesis Route For Indazole Derivativesmentioning

confidence: 99%

Recent Advances in Indazole-Containing Derivatives: Synthesis and Biological Perspectives

2018

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Indazole-containing derivatives represent one of the most important heterocycles in drug molecules. Diversely substituted indazole derivatives bear a variety of functional groups and display versatile biological activities; hence, they have gained considerable attention in the field of medicinal chemistry. This review aims to summarize the recent advances in various methods for the synthesis of indazole derivatives. The current developments in the biological activities of indazole-based compounds are also presented.

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Section: Synthesis Route For Indazole Derivativesmentioning

confidence: 99%

Recent Advances in Indazole-Containing Derivatives: Synthesis and Biological Perspectives

2018

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“…In 2017, Chang and Yu proposed a strategy that, in the presence of potassium iodide, performs iodinepromoted oxidative cyclization of diaryl and tert-butyl aryl ketone hydrazone 173 to achieve direct aryl CÀ H amination and generate 1H-indazole 174 (Scheme 30). [53] Notably, this approach does not involve transition metals and is simple to operate. The indazole derivative can be obtained easily in an efficient, scalable way.…”

Section: Cyclization Of Hydrazones With Adjacent Unsaturated Bonds Under Metal-free Conditionsmentioning

confidence: 99%

Update on the Synthesis of N‐Heterocycles via Cyclization of Hydrazones (2017–2021)

Meng

et al. 2021

Adv Synth Catal

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Hydrazones, as universal structural units, are useful synthons for the formation of carbonnitrogen and nitrogenÀ heteroatom bonds. Thus, they provide new methods of constructing nitrogen-containing heterocycles. In recent years, especially between 2017 and 2021, many efforts have been made to exploit hydrazone-based reactions in efforts to develop more powerful and effective pathways towards the synthesis of various multifunctional heterocyclic compounds. However, despite the tremendous amount of work that has been published over the past five years, no review has been published that summarizes the significant progress in the preparation of nitrogen heterocycles via intramolecular cyclization of hydrazones with adjacent unsaturated bonds or intermolecular cyclization of hydrazones with unsaturated systems. Therefore, this review summarizes the hydrazone-based cyclization strategies used to synthesize nitrogen-containing heterocycles over the past five years. It discusses the corresponding reaction scopes, limitations, mechanisms, and problems. Cyclization of Hydrazones with Unsaturated Systems 3.3. Cyclization of Hydrazones with Unsaturated Systems Under Metal-Free Conditions 4. Conclusion

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“…In view of the abovementioned interest, an increasing number of approaches for the synthesis of 1H-indazoles has been recently reported, including 1,3-dipolar cycloaddition reaction of α-diazomethylphosphonates with o-(trimethylsilyl)phenyl triflate in the presence of CsF [13], Cu 2+ -mediated N−N bond formation from ketimines in the presence of oxygen [14], Pd 2+mediated oxidative benzannulation from pyrazoles and internal alkynes [15], Pd-catalyzed Aza-Nenitzescu reaction of hydrazones and p-benzoquinones [16], and Co 3+ /Cu 2+ -catalyzed C−N/N−N coupling of imidates with anthranils as both aminating reagents and organic oxidants [17]. Additional established routes to 1H-indazoles comprise transition metal-catalyzed [18][19][20] and metal-free [21,22] intramolecular amination by oxidative C−H bond functionalizations. These methods showed significant improvement with respect to the substrate scope and reaction conditions.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of N-phenyl- and N-thiazolyl-1H-indazoles by copper-catalyzed intramolecular N-arylation of ortho-chlorinated arylhydrazones

Barbosa¹,

Paveglio²,

Pereira³

et al. 2022

Beilstein J. Org. Chem.

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The broad application of 1H-indazoles has prompted the development of several approaches for the synthesis of such compounds, including metal-free, palladium-, or copper-promoted intramolecular N-arylation of in situ-generated or isolated o-haloarylhydrazones. Such methods mainly start from o-bromo derivatives due to the better yield observed when compared to those obtained from o-chloroarylhydrazones. However, the o-chloroarylaldehydes and o-chloroarylketones used to prepare the arylhydrazones are more commercially available and less expensive than brominated analogs. Seeking to cover a lack in the literature, this work reports a convenient protocol for the synthesis of N-phenyl- and N-thiazolyl-1H-indazoles by copper-catalyzed intramolecular N-arylation of o-chlorinated arylhydrazones. Therefore, a series of seven N-phenyl derivatives and a series of six novel N-thiazolyl derivatives was obtained in 10–70% and 12–35% yield, respectively, after stirring the o-chlorinated arylhydrazones, CuI, KOH, and 1,10-phenantroline for 12–48 hours in DMF at 120 °C. The products were isolated by column chromatography on silica gel. All products were fully characterized by HRMS as well as 1H and 13C NMR spectroscopy. Thus, this approach is valuable for promoting the synthesis of N-phenyl-1H-indazoles in a higher yield than that reported in the literature using copper catalysis and the same substrates. This study also prompted the first reported synthesis of pharmacologically interesting N-thiazolyl derivatives.

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Divergent Synthesis of 1H‐Indazoles and 1H‐Pyrazoles from Hydrazones via Iodine‐Mediated Intramolecular Aryl and sp³ C–H Amination

Cited by 34 publications

References 45 publications

Recent Advances in Indazole-Containing Derivatives: Synthesis and Biological Perspectives

Recent Advances in Indazole-Containing Derivatives: Synthesis and Biological Perspectives

Update on the Synthesis of N‐Heterocycles via Cyclization of Hydrazones (2017–2021)

Synthesis of N-phenyl- and N-thiazolyl-1H-indazoles by copper-catalyzed intramolecular N-arylation of ortho-chlorinated arylhydrazones

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