Synthesis of 1,3,4‐Oxadiazole‐Based Aromatic and Heterocyclic/Phenylpyrazole Derivatives

Wang, Liya; Chang, En-Chiuan; Yeh, Mou‐Yung; Chung, Yu Hsuan; Huang, Jow Lay; Wong, Fung Fuh

doi:10.1002/hc.21151

Cited by 3 publications

References 37 publications

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[3 + 2] Cycloadditions of Azomethine Imines

Grošelj

Svete

2020

Organic Reactions

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In spite of their late discovery in the middle of 20 th century, the importance of azomethine imines and their [3+2] cycloaddition reactions has grown constantly throughout the decades. Today, [3+2] cycloadditions of azomethine imines have become indispensable in the preparation of pyrazole derivatives with all degrees of saturation. The structural diversity of azomethine imines is wide and comprises acyclic, C , N ‐cyclic, N , N ‐cyclic, and C , N , N ‐cyclic 1,3‐dipoles. Although electron‐deficient dipolarophiles are preferred, electron‐rich dipolarophiles, such as enol ethers and enamines, are also commonly used in these reactions. Compared to cyclocondensation methods and [3+2] cycloadditions with diazoalkanes and nitrile imines, [3+2] cycloadditions with azomethine imines provide access to a greater diversity of pyrazole derivatives with all degrees of saturation. As with other 1,3‐dipolar cycloadditions, a concerted and nearly synchronous mechanism has been proposed for most [3+2] cycloadditions of azomethine imines, although a stepwise mechanism may be viable in some cases. Several examples of asymmetric [3+2] cycloadditions of azomethine imines that afford non‐racemic cycloadducts with high enantioselectivity have been reported. These asymmetric cycloadditions are performed with various types of transition metal catalysts and organocatalysts, and indicate their potential for the asymmetric synthesis of saturated pyrazole derivatives. Finally, many examples of copper‐catalyzed and thermal, strain‐promoted [3+2] cycloadditions of azomethine imines (in particular sydnones) clearly indicate wide applicability of these reactions in bioconjugation, fluorescent labelling, materials functionalization, and other applications outside the realm of pure organic synthesis.

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[3 + 2] Cycloadditions of Azomethine Imines

Grošelj

Svete

2020

Organic Reactions

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Recent developments in the chemistry of sydnones and sydnone imines

Cherepanov

Moiseev

2020

Advances in Heterocyclic Chemistry

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[3 + 2]-Cycloaddition reaction of sydnones with alkynes

Hladíková¹,

Váňa²,

Hanusek³

2018

Beilstein J. Org. Chem.

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This review covers all known examples of [3 + 2]-cycloaddition between sydnones and both terminal as well as internal alkynes/cycloalkynes taken from literature since its discovery by Huisgen in 1962 up to the current date. Except enumeration of synthetic applications it also covers mechanistic studies, catalysis, effects of substituents and reaction conditions influencing reaction rate and regioselectivity.

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Synthesis of 1,3,4‐Oxadiazole‐Based Aromatic and Heterocyclic/Phenylpyrazole Derivatives

Cited by 3 publications

References 37 publications

[3 + 2] Cycloadditions of Azomethine Imines

[3 + 2] Cycloadditions of Azomethine Imines

Recent developments in the chemistry of sydnones and sydnone imines

[3 + 2]-Cycloaddition reaction of sydnones with alkynes

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