Hydrazone

About: Hydrazone is a research topic. Over the lifetime, 4853 publications have been published within this topic receiving 65160 citations. The topic is also known as: hydrazone.

An efficient one-pot catalyzed synthesis of 2,5-disubstituted-1,3,4-oxadiazoles and evaluation of their antimicrobial activities

Abstract: One-pot synthesis of 1,3,4-oxadiazole derivatives was achieved by treatment of 2-((4-(phenoxathiin-2-yl)phthalazin-1-yl)oxy)acetohydrazide with aromatic aldehydes in the presence of cerium(IV) ammonium nitrate in dichloromethane. This facile method was confirmed by the cyclization–oxidation reaction of the corresponding hydrazone by cerium(IV) ammonium nitrate to afford the same 1,3,4-oxadiazoles. Also, the reaction of 2-((4-(phenoxathiin-2-yl)phthalazin-1-yl)oxy)acetohydrazide with aromatic carboxylic acids in the presence of cerium(IV) ammonium nitrate in polyethylene glycol afforded 1,3,4-oxadiazole derivatives. The structural formulae of all products were confirmed and characterized by elemental analyses and spectral data. Most of the synthesized products were evaluated for their antibacterial and antifungal activities and showed potent to weak activity.

Structurally diverse copper(II) complexes with pyridazine-integrated with pyrazine–Schiff base ligand featuring an easily lost proton in the hydrazone backbone

Abstract: To probe the coordination approach of pyridazine and pyrazine ligands, five new complexes of [CuII2L2Cl2] (1), [CuII(L-H)(NO3)(H2O)2](NO3)(H2O) (2), {[CuII(L-H)(H2O)](ClO4)2(H2O)}n (3), [CuII2L2(OH)](NO3)(H2O)2 (4), [CuII2L2(OH)](ClO4) (5) based on Schiff base ligand (E)-3-chloro-6-[2-(pyrazin-2-ylmethylene)hydrazinyl]pyridazine (HL) bearing pyridazinyl and pyrazinyl groups have been synthesized and characterized by IR spectra, elemental analyses, the bond valence sum (BVS) analyses, powder X-ray diffraction (PXRD) analyses, X-ray single crystal diffraction and density function theory calculations. The structures of 1, 2 and 3 suggest that the second nitrogen donors of the pyrazinyl unit can link with other metal ions to construct a higher dimensional architecture by the reaction of HL with Cu(ClO4)2 [CuCl2 for 1, Cu(NO3)2 for 2 and Cu(ClO4)2 for 3]. The structures of 4 and 5 indicate that additional donor units of the pyridazinyl chromophore can bind multiple metal ions to form a multi-metallic cluster, when the protons of the hydrazone backbones are abstracted in the presence of triethylamine to strengthen the coordination behavior of the second nitrogen atom. However, for 1, the protons of the hydrazone backbone are lost with or without triethylamine and the additional nitrogen atoms of the pyrazinyl and pyridazinyl groups are not found to connect to other metal ions, which can probably be assigned to the strong coupling effect of chlorine ions. Magnetic measurements display weak antiferromagnetic coupling between the copper(II) ions in 1 and 5, and ferromagnetic coupling in 3. In addition, the antioxidant activities of HL and 1–5 were also studied.

Stereoisomerization in heterocyclic hydrazones derived from 2-acylpyridines and their oxidative cyclization with mercury(II) acetate and lead tetra-acetate to fused 1,2,4-triazoles and 1,2,3-triazolium systems

Abstract: Hydrazones prepared by coupling 2-acylpyridines with arylhydrazines were isolated predominantly as E-isomers when the acyl substituent R was small (H or Me). When R was a phenyl group significant yields of Z-isomers, containing an intramolecular hydrogen bond, were also isolated. Oxidation reactions of these hydrazones were not influenced by the E- or Z-geometry of the substrate contrary to earlier reports. A common metallo intermediate with a Z-structure was encountered in the oxidations of the E- and Z-pyridine 2-carbaldehyde 2-pyridylhydrazone with mercuric acetate. In oxidations of a series of hydrazones with lead tetra-acetate the product controlling factor was the nature of the methine substituent R. For ketone derivatives (R ≠ H) oxidation to fused 1,2,3-triazolium systems occurred via a 5-exo-tet cyclization with E- and Z-hydrazone substrates. For aldehyde systems (R = H) the oxidation involved dehydrogenation to a nitrilimine and gave products by solvent addition or a 5-endo-dig cyclization to fused 1,2,4-triazolo systems.

Syn/anti isomerization of 2,4-dinitrophenylhydrazones in the determination of airborne unsymmetrical aldehydes and ketones using 2,4-dinitrophenylhydrazine derivation.

Abstract: Aldehydes and ketones readily react with 2,4-dinitrophenylhydrazine (2,4-DNPH) to form the corresponding hydrazones. This reaction has been frequently used for the quantification of airborne carbonyl compounds. Since unsymmetrical aldehydes and ketones are known to form isomeric 2,4-dinitrophenylhydrazones (syn/ anti-isomers), the influence of isomerization on the practicability and accuracy of the 2,4-DNPH-method using 2,4-dinitrophenylhydrazine-coated solid sorbent samplers has been studied with three ketones (methyl ethyl ketone (MEK), methyl isopropyl ketone (MIPK), and methyl isobutyl ketone (MIBK)). With all three ketones the reaction with 2,4-DNPH resulted in mixtures of the isomeric hydrazones which were separated by HPLC and GC and identified by mass spectroscopy and (1)H nuclear magnetic resonance spectroscopy. The isomers show similar chromatographic behaviour in HPLC as well as in GC, thus leading to problems in quantification and interpretation of chromatographic results.

One pot synthesis and biological activity evaluation of novel Schiff bases derived from 2-hydrazinyl-1,3,4-thiadiazole.

Abstract: Considering the structural features of a group of known potent inhibitors of human platelet aggregation containing hydrazone structural backbone, a series of novel hydrazone derivatives of 2-hydrazinyl-1,3,4-thiadiazole were synthesized using a one-pot process and tested for their inhibitory activity against platelet aggregation induced by arachidonic acid and ADP. Among the derivatives, compounds 3l, 3o and 3p exhibited the highest antiplatelet aggregation activity. The derivatives were also screened for their potential antimycobacterial activity and compounds 3g, 3k, 3p and 3q were among the most active compounds.