The use of enaminones and enamines as effective synthons for MSA-catalyzed regioselective synthesis of 1,3,4-tri- and 1,3,4,5-tetrasubstituted pyrazoles

A copper-promoted aerobic oxidative [3+2] cycloaddition reaction for the synthesis of various substituted pyrazoles from N,N-disubstituted hydrazines with alkynoates in the presence of bases is developed. This work involves a direct C(sp3)–H functionalization and the formation of new C–C/C–N bonds. In this strategy, inexpensive and easily available Cu2O serves as the promoter and air acts as the green oxidant. The reaction exhibits the advantages of high atom and step economy, high regioselectivity, and easy operation.

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“…. 51 Eluent, petroleum ether/ethyl acetate (v/v = 10/1); yellow solid in 41% yield (10.7 mg, 0.04 mmol); mp 107.0−108.0 °C; IR (KBr, cm…”

Section: -(13-diphenyl-1h-pyrazol-4-yl)ethan-1-one (4r)mentioning

confidence: 99%

Copper-Promoted Aerobic Oxidative [3+2] Cycloaddition Reactions of N,N-Disubstituted Hydrazines with Alkynoates: Access to Substituted Pyrazoles

et al. 2023

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“…[90] Thus far, chemists have developed numerous methods for the selective construction of N-heterocycle skeletons using organocatalysis. [91][92][93][94][95][96][97][98][99][100][101][102][103][104][105]…”

Section: Cyclization Of Hydrazones With Unsaturated Systems 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 2019, Qin developed a methanesulfonic acid catalyzed procedure using N,N-dimethyl enaminones as effective synthons for the regioselective synthesis of 1,3,4-trisubstituted pyrazoles (Scheme 29). 31 The reaction of the enaminone and hydrazone, installing an electron-withdrawing or electron-donating group, proceeded smoothly to deliver the corresponding product in moderate to good yield. The process also worked with heteroaryl and alkyl enaminones.…”

Section: Synthesis Of Five-membered Heterocyclesmentioning

confidence: 99%

Recent Advances in Organic Synthesis Based on N,N-Dimethyl Enaminones

Huang

2020

Synthesis

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Enaminones are gaining increasing interest because of their unique properties and their importance in organic synthesis as versatile building blocks. N,N-Dimethyl enaminones offer a better leaving group (a dimethylamine group) than other enaminones, and allow further elaboration via a range of facile chemical transformations. Over the past five years, there have been an increasing number of reports describing the synthetic applications of N,N-dimethyl enaminones. This review provides a comprehensive overview on the synthetic applications of N,N-dimethyl enaminones that have been reported since 2016.1 Introduction2 Direct C(sp2)–H α-Functionalization2.1 Synthesis of α-Sulfenylated N,N-Dimethyl Enaminones2.2 Synthesis of α-Thiocyanated N,N-Dimethyl Enaminones2.3 Synthesis of α-Acyloxylated N,N-Dimethyl Enaminones3 Functionalization Reactions via C=C Double Bond Cleavage3.1 Synthesis of Functionalized Methyl Ketones3.2 Synthesis of α-Ketoamides, α-Ketoesters and 1,2-Diketones3.3 Synthesis of N-Sulfonyl Amidines4 Construction of All-Carbon Aromatic Scaffolds4.1 Synthesis of Benzaldehydes4.2 Synthesis of the Naphthalenes5 Construction of Heterocyclic Scaffolds5.1 Synthesis of Five-Membered Heterocycles5.2 Synthesis of Six-Membered Heterocycles5.3 Synthesis of Quinolines 5.4 Synthesis of Functionalized Chromones5.5 Synthesis of Other Fused Polycyclic Heterocycles6 Conclusions and Perspectives

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The use of enaminones and enamines as effective synthons for MSA-catalyzed regioselective synthesis of 1,3,4-tri- and 1,3,4,5-tetrasubstituted pyrazoles

Abstract: In the present work, an efficient regioselective synthesis of 1,3,4-tri- and 1,3,4,5-tetrasubstituted pyrazoles via a methanesulfonic acid (MSA)-catalyzed reaction of hydrazones with enaminones or enamines is reported.

Cited by 15 publications

References 28 publications

Copper-Promoted Aerobic Oxidative [3+2] Cycloaddition Reactions of N,N-Disubstituted Hydrazines with Alkynoates: Access to Substituted Pyrazoles

Copper-Promoted Aerobic Oxidative [3+2] Cycloaddition Reactions of N,N-Disubstituted Hydrazines with Alkynoates: Access to Substituted Pyrazoles

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

Recent Advances in Organic Synthesis Based on N,N-Dimethyl Enaminones

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