Synthesis of 2-Aminopyrroles Via Metal-Free Annulation of Ynamides with 2<i>H</i>-Azirines

Jiao, Lianhong; Wang, Yanan; Ding, Lixia; Zhang, Chaofeng; Wang, Xiao-Na; Chang, Junbiao

doi:10.1021/acs.joc.2c02103

Cited by 7 publications

(4 citation statements)

References 83 publications

(26 reference statements)

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“…BF 3 •Et 2 O‐catalyzed annulation of ynamides with 2H ‐azirines have been successively achieved to overwhelm this limitation (Scheme 27). [47] The reaction utilizing Lewis acid is preferred than the one with Brønsted acids such as TfOH and Tf 2 NH. This strategy distinctively begins from the activation of 2H ‐azirines to give highly electrophilic intermediate, which undergoes a cleavage of C−N single bond attacked by ynamide or a nucleophilic addition of ynamide to C=N double bond, respectively.…”

Section: Reaction Of 2h‐azirinesmentioning

confidence: 99%

2H‐Azirines: Recent Progress in Synthesis and Applications

Xu,

Zeng,

Luo

et al. 2024

Eur J Org Chem

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2H‐arizines are important three‐membered heterocycles in organic chemistry. Recently, many advances in the synthesis and functionalization of 2H‐arizines have been reported. Neber rearrangement, isomerization of isoxazole, oxidation of enamine, C–H bond activation, decomposition of vinyl azide, functionalization of alkyne, and multi‐step synthesis have been developed for the efficient assembly of 2H‐azirines. As versatile and highly strained three‐membered unsaturated heterocycles, 2H‐azirines can be used as distinctive building blocks towards significant functional groups, and have attracted extensive attention for the fabrication of numerous heterocycles. Recent studies have focused on [3+n] ring‐expansion reactions, nucleophilic addition of C=N double bond or continuous nucleophilic addition followed by cyclization, ring‐opening of 2H‐azirines to acyclic compounds, and substitution of sp3‐C‐H of 2H‐azirines. One of the most critical challenges is seeking for a selective opening of the specific three bonds of the strained azirine circle, some of what can be achieved on the basis of metal catalyst, photocatalysis, or combination of metal catalyst and photocatalysis. In this review, recent advances involving the synthesis and reactivity of 2H‐arizines accompanied with challenges and breakthroughs are summarized. The review mainly covers the period from 2019 to 2023.

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Section: Reaction Of 2h‐azirinesmentioning

confidence: 99%

2H‐Azirines: Recent Progress in Synthesis and Applications

Xu,

Zeng,

Luo

et al. 2024

Eur J Org Chem

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“…The 2H-azirines are the simplest unsaturated nitrogen heterocycles, possessing great potential in organic synthesis [1][2][3][4][5][6][7][8][9][10]. Mainly, this is due to the presence of an electrophilic C=N bond in a highly strained azirine ring, which can readily undergo addition of various nucleophiles.…”

Section: Introductionmentioning

confidence: 99%

Triethylamine-Promoted Oxidative Cyclodimerization of 2H-Azirine-2-carboxylates to Pyrimidine-4,6-dicarboxylates: Experimental and DFT Study

Zakharov,

Sakharov,

Novikov

et al. 2023

Molecules

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An unprecedented oxidative cyclodimerization reaction of 2H-azirine-2-carboxylates to pyrimidine-4,6-dicarboxylates under heating with triethylamine in air is described. In this reaction, one azirine molecule undergoes formal cleavage across the C-C bond and another across the C=N bond. According to the experimental study and DFT calculations, the key steps of the reaction mechanism include nucleophilic addition of N,N-diethylhydroxylamine to an azirine to form an (aminooxy)aziridine, generation of an azomethine ylide, and its 1,3-dipolar cycloaddition to the second azirine molecule. The crucial condition for the synthesis of pyrimidines is generation of N,N-diethylhydroxylamine in the reaction mixture in a very low concentration, which is ensured by the slow oxidation of triethylamine with air oxygen. Addition of a radical initiator accelerated the reaction and resulted in higher yields of the pyrimidines. Under these conditions, the scope of the pyrimidine formation was elucidated, and a series of pyrimidines was synthesized.

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“…13 Our interest in the development of metal-free reactions of ynamides inspired us to develop the nonmetal-catalyzed Ficini reaction of ynamides. 14 Herein, we disclose our first success in a nonmetal-catalyzed regiospecific Ficini reaction of ynamides with enones under the catalysis of Tf 2 NH, 15 leading to the practical and atom-economical synthesis of cyclobutenamides in generally good to excellent yields (Scheme 1e).…”

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confidence: 99%