Hydrazones as New 4-Electrons Three Atomic Centers in Cycloaddition Reactions: A Novel Approach for the Synthesis of Pyrazole Derivatives

Ibrahim, Yehia A.; Abdou, Sadek E.; Selim, S. F.

doi:10.3987/r-1982-05-0819

Cited by 13 publications

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“…Hydrazones can act as four π‐electron, three‐atomic center (1,3‐dipole) systems to react with olefins to form five‐membered rings 22–28. The resulting intermediate might be a good hydrogen atom donor because the resulting carbon‐centered radical is surrounded by both an electron‐donating group (nitrogen lone pair of electrons) and an electron‐withdrawing group (carbonyl).…”

Section: Resultsmentioning

confidence: 99%

Hydrazone initiators for vinyl polymerizations

Wolf¹,

Warakomski²,

Staples³

et al. 2001

J. Polym. Sci. A Polym. Chem.

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A series of hydrazones were prepared and tested for their ability to act as free‐radical initiators for vinyl monomers. The most active initiators were the tertiary butyl hydrazones of aromatic, aliphatic ketones. The most reactive vinyl monomers were acrylate‐type monomers, with methacrylate‐type monomers being somewhat less reactive. When the most reactive hydrazone initiators, such as compound 1, were added to ambient‐temperature solutions of acrylate monomers, such as aqueous sodium acrylate or aqueous acrylamide, polymerizations to hard gels occured within 1 min. In some cases of vinyl polymerizations, these hydrazone initiators can act as low‐temperature alternatives to redox initiators. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1391–1402, 2001

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Section: Resultsmentioning

confidence: 99%

Hydrazone initiators for vinyl polymerizations

Wolf¹,

Warakomski²,

Staples³

et al. 2001

J. Polym. Sci. A Polym. Chem.

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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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Reactions with Maleimides: Syntheses of New Furylpyrazole Derivatives

Ghabrial

Arief

Abdou

1985

Archiv der Pharmazie

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New furylpyrrolopyrazole derivatives were synthesised by reacting N-arylmaleimides with furfural phenylhydrazone. The products are to be tested for their biological activities and for chemical transformations. Umsetzungen mit Maleinhiden: Synthese e w e r neuer Furylpyrazol-DerivateDurch Umsetzungen von N-Arylmaleinimiden mit Furfuralphenylhydrazon werden neue Furylpyrrolopyrazol-Derivate synthetisiert. Die erhaltenen Verbindungen sind interessant sowohl im Hinblick auf die Testung ihrer biologischen Aktivitat als auch fur weitere chemische Abwandlungen.The reported bacteriostatic, bacteriocidal and fungicidal properties of furan and pyrazole derivatives'-s' prompted our interest for the synthesis of heterocyclic derivatives containing these ring systems. It has been reported also that compounds containing the -CO-NH-CO-and -CO-NR-COmoieties are very effective and peristent foliage fungicides, especially for control of apple and pear scab and seed dressings against many soil and seed-borne diseases6.'). In addition, diverse biological activities have been reportes for the pyrrolo-pyrazole derivatives'.''. The reaction of Narylmaleimides with furfural phenylhydrazone seemed a logic route for the synthesis of derivatives containing collectively the above functions. The synthesised compounds seem promising for biological activity studies and also for further chemical transformations.Thus, it has been found that furfural phenylhydrazone (1) reacted with the N-arylmaleimides 2a-j in boiling toluene or by fusion of the reactants to give the 5-furylpyrrolino[3,4-d]pyrazolidine-2,6-dione derivatiaves 3a-j in excellent yields. To our knowledge there is n o literature dealing with the use of hydrazones as 4-electron three atomic centers in dipolar cycloaddition reactions with the exception of our last publication"). It is noteworthy to report, here, that the reaction products were only one compound in each case in contrast to the previous findings for the phenyl-counter analogues").The structure assigned for 3a-j was based on analytical data and spectral studies. Thus, the I R spectra of 38-j revealed absorption bands at 1790-1720 and 1710-1690 cm-' attributed to the presence of the -CO-NR-CO-grouping besides the bands related to the presence of the N H group at about 3200 cm-'. 'H-NMR of 3b and 3e as typical examples of the series revealed a pattern which is completely interpreted in terms of structure 3 only.

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Hydrazones as New 4-Electrons Three Atomic Centers in Cycloaddition Reactions: A Novel Approach for the Synthesis of Pyrazole Derivatives

Cited by 13 publications

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Hydrazone initiators for vinyl polymerizations

Hydrazone initiators for vinyl polymerizations

[3 + 2] Cycloadditions of Azomethine Imines

Reactions with Maleimides: Syntheses of New Furylpyrazole Derivatives

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