[4 + 2] Annulation Reaction of <i>In Situ</i> Generated Azoalkenes with Azlactones: Access to 4,5-Dihydropyridazin-3(2<i>H</i>)-Ones

Yuan, Wei‐Cheng; Quan, Bao-Xue; Zhao, Jian‐Qiang; Wang, Zhen-Hua; Zhou, Ming‐Qiang

doi:10.1021/acs.joc.0c01592

Cited by 16 publications

(6 citation statements)

References 69 publications

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“…The [4+2] annulation reaction of 1,2-diaza-1,3-dienes 89 with azlactones 90 produces dihydropyridazinones 91 , in moderates to good yields [ 45 ]. Using Na 2 CO 3 as a base, the reaction was conducted at room temperature in toluene with an N 2 atmosphere.…”

Section: Synthesis Of Heterocycles From 12-diaza-13-dienesmentioning

confidence: 99%

Diaza-1,3-butadienes as Useful Intermediate in Heterocycles Synthesis

et al. 2022

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Many heterocyclic compounds can be synthetized using diaza-1,3-butadienes (DADs) as key structural precursors. Isolated and in situ diaza-1,3-butadienes, produced from their respective precursors (typically imines and hydrazones) under a variety of conditions, can both react with a wide range of substrates in many kinds of reactions. Most of these reactions discussed here include nucleophilic additions, Michael-type reactions, cycloadditions, Diels–Alder, inverse electron demand Diels–Alder, and aza-Diels–Alder reactions. This review focuses on the reports during the last 10 years employing 1,2-diaza-, 1,3-diaza-, 2,3-diaza-, and 1,4-diaza-1,3-butadienes as intermediates to synthesize heterocycles such as indole, pyrazole, 1,2,3-triazole, imidazoline, pyrimidinone, pyrazoline, -lactam, and imidazolidine, among others. Fused heterocycles, such as quinazoline, isoquinoline, and dihydroquinoxaline derivatives, are also included in the review.

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Section: Synthesis Of Heterocycles From 12-diaza-13-dienesmentioning

confidence: 99%

Diaza-1,3-butadienes as Useful Intermediate in Heterocycles Synthesis

et al. 2022

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“…[121] Two months later, Zhao and Yuan developed a [4 + 2] cyclization reaction for the synthesis of 4,5-dihydropyridazin-3(2H)-ones using hydrazones 426 and azlactones as starting materials (Scheme 60d). [122] At the end of the same year, Liu and Zheng established an economical, mild, and valuable [3 + 2] cycloaddition reaction and obtained a number of functionalized pyrazoline derivatives 433 with significant yields (Scheme 64e). [123] Scheme 61.…”

Section: Intermolecular Cyclizationmentioning

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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“…Dihydropyridazinones, especially the 4,5-dihydropyridazin-3(2 H )-one motifs, are important structural cores frequently found in numerous bioactive compounds, which possess a rich array of pharmacological and biological activities. − Consequently, many efforts have been dedicated to finding synthetic routes to 4,5-dihydropyridazin-3(2 H )-ones. − However, construction of the chiral 4,5-dihydropyridazin-3(2 H )-ones always needs suitable reagents or chiral resolution, − which limits their application and promotes the development of more direct and asymmetric synthetic strategies. In this regard, NHC-catalyzed [3 + 3] annulation between dinucleophilic hydrazones and enals has been developed. − Catalytic reactions of α-chloro hydrazones with acetic acids using an isothiourea catalyst are also attractive. , Nevertheless, further studies show that only acetic acids with α-aryl- or alkenyl-substituents are suitable, and substitution with an α-alkyl group is much less active.…”

Section: Introductionmentioning

confidence: 99%

Mechanism, Chemoselectivity, and Stereoselectivity of an NHC-Catalyzed Reaction of Aldehydes and Hydrazones: A DFT Study

Li,

Kang,

Xiao

et al. 2024

J. Phys. Chem. A

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To elucidate the mechanism and origins of chemoand enantioselectivities of the reaction between aliphatic aldehydes and hydrazones catalyzed by triazolium-derived NHC, density functional theory computations have been performed. According to our calculated results, the whole catalytic cycle for the formation of dihydropyridazinones proceeds via the initial nucleophilic addition of NHC to an aliphatic aldehyde, followed by the concerted intramolecular proton transfer and C−Cl bond cleavage. Subsequent deprotonation generates an enolate intermediate. The enolate intermediate then undergoes 1,4-addition to hydrazone to construct a new carbon−carbon bond. The following ring-closure would lead to a six-membered ring intermediate, which, upon the release of NHC, affords the final product dihydropyridazinone. The computation results reveal that intramolecular proton transfer is significantly promoted by the Brønsted acid DIPEA•H + . The carbon−carbon bond formation step could determine not only the chemoselectivity but also the stereoselectivity and lead to the Sisomer product. It was found that the stereoselectivity arises from a combination of weak interactions, including C−H•••O, C−H•••N, C−H•••π, and LP•••π. NHC could enhance the nucleophilicity of the aliphatic aldehyde and facilitate further reaction with hydrazone. This work could be beneficial for the development of new catalytic strategies in the future.

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[4 + 2] Annulation Reaction of In Situ Generated Azoalkenes with Azlactones: Access to 4,5-Dihydropyridazin-3(2H)-Ones

Cited by 16 publications

References 69 publications

Diaza-1,3-butadienes as Useful Intermediate in Heterocycles Synthesis

Diaza-1,3-butadienes as Useful Intermediate in Heterocycles Synthesis

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

Mechanism, Chemoselectivity, and Stereoselectivity of an NHC-Catalyzed Reaction of Aldehydes and Hydrazones: A DFT Study

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