Azomethine Hydrogen Research Articles

A Systematic Review on Synthetic and Antimicrobial Bioactivity of the Multifaceted Hydrazide Derivatives

: To overcome the upsurge of antimicrobial resistance that has emerged in recent years, there is a need for the development of newer hits having satisfying anti-infective activity. Hydrazides incorporated with an azomethine hydrogen account for a cardinal class of molecules for the development of newer derivatives. Hydrazide derivatives have gained considerable interest of medicinal chemists owing to their diverse bioactivity. In the present review, we have attempted to compile the recent trends in the synthesis of hydrazides and their substituted derivatives. The structural features that lead to the desired antimicrobial activity are highlighted, which will lead the way for synthetic and medicinal chemists to focus on newer designs in this arena.

Experimental and theoretical studies of (Z)-N-(2-chlorobenzylidene) naphthalen-1-amine and (Z)-N-(3-nitrobenzylidene)naphthalen-1-amine, and their corrosion inhibition properties

Two Schiff base compounds, (Z)-N-(2-chlorobenzylidene) naphthalen-1-amine (CBN) and (Z)-N-(3-nitrobenzylidene)naphthalen-1-amine (NBN) were synthesized by the reaction between 1-naphthylamine and 2-chlorobenzaldehyde or 3-nitrobenzaldehyde respectively. The compounds were characterized using elemental analyses, NMR (1H and 13C), Fourier transform infra-red (FTIR) and mass spectroscopic techniques. From the 1HNMR, the azomethine hydrogen (CHN) gave a singlet at 8.95 ppm for CBN and 8.90 ppm for NBN. The molecular ion peaks from the mass spectra results are 266.07 and 277.09 g/mol for CBN and NBN respectively. The structures of the compounds were further verified using density functional theory (DFT) which showed the role of the electrons towards corrosion inhibition. The results of the electrochemical techniques using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) revealed that the two compounds are very good corrosion inhibitors with CBN showing better properties.

Colloid and nanodimensional catalysts in organic synthesis: VIII. Hydrogenation of C=N bond with hydrogen in the presence of colloid nickel

Hydrogenation of azomethines with hydrogen at atmospheric pressure using nickel nanoparticles as catalyst was carried out. Reaction may be used for the preparation of secondary amines under mild conditions on an available catalyst. Continuation of studies will lead to development of a convenient method for the reductive amination of carbonyl compounds.

Electronic spectral studies of some fluorescent probes: A comparison of two approaches

Schiff base derivatives were synthesized and characterized by NMR spectra, mass and CHN analysis. The fluorescence properties of these dyes are strongly solvent dependent and the wavelength of maximum fluorescence emission shifts to red. The Kamlet–Taft and Catalan’s solvent scales were found to be the most suitable for describing the solvatochromic shifts of the absorption and fluorescence emission. From the NMR chemical shifts and DFT studies, it was found that the azomethine hydrogen is anti to the amine aryl ring i.e., these dyes exist in anti conformation. DFT calculation was also carried out to determine the orientation of hydroxyl group in more stabilized minimum energy conformation.

Synthesis and characterization of water-soluble zinc(II) Schiff-base complexes derived from amino acids and 3-formyl-4-hydroxybenzyl-triphenylphosphonium chloride

Tridentate Schiff-base ligands derived from condensation of 3-formyl-4-hydroxybenzyl-triphenylphosphonium chloride with glycine, L-alanine, L-valine, L-leucine and L-phenylalanine in the presence of Zn(OAc)2 · 2H2O form five new water-soluble Zn(II) complexes, which were characterized by elemental analyses, IR, electronic absorption and 1H, 13C NMR spectroscopies. In the IR spectra of the complexes, the difference between the asymmetric and the symmetric carboxylate stretching frequencies is larger than ∼210 cm−1, which implies that the carboxylate groups are monodentate. UV-Vis electronic absorption studies show that Zn(II) functions as a trap for the Schiff-base intermediate. Schiff-base complexes formation were confirmed by the appearance of new signals in the 1H NMR for the azomethine hydrogen at ∼8 ppm and condensed L-amino acids at 3.4–3.8 ppm (C(3)–H). These complexes are formed through coordination of the ONO from the carboxyl, imino and phenoxy groups of the ligands to Zn(II).

Synthesis and spectroscopic studies of the optically active copper(II), cobalt(II) and nickel(II) complexes with Schiff bases N, N′-( 1R, 2R)(−)-1,2-cyclohexylenebis(3-methoxybenzylideneiminato), N, N′-( 1R, 2R)(−)-1,2-cyclohexylenebis(5-methoxybenzylideneiminato) and X-ray diffraction structure of the [Cu(II)(1 R,2 R)(−)chxnbis(5-methylbenzylideneiminato) 2

Schiff bases obtained from N, N′-(1 R,2 R)-cyclohexanediamine and 2-hydroxy-3-methoxybenzaldehyde, 2-hydroxy-5-methoxybenzaldehyde or 2-hydroxy-5-methylbenzaldehyde have been used as ligands for copper(II), cobalt(II) and nickel(II). The complexes were characterized with UV–Vis, circular dichroism (CD), IR and 1H and 13C NMR spectroscopy and X-ray crystal structure was solved for [Cu(II)(1 R, 2 R)(−)chxn(5-methylba) 2]. CD spectra in acetonitrile solution revealed exciton coupled π → π*, LMCT and d–d transitions in Ni(II), Co(II) and Cu(II) complexes. CD data are characteristic for tetrahedral distortion from the planarity of the chelate ring and λ conformation of the cyclohexane bridge. The 1H NMR paramagnetic spectra of Co(II) complexes revealed the most upfield shifted resonance at −60 ppm assigned to C H N and at −28 ppm to C(5′)H of the phenyl ring. NOE NMR of the Schiff bases and nickel complexes were measured with the saturation of proton at C H N . NOE experiment revealed interaction of the azomethine hydrogen with protons from cyclohexyl groups, phenyl ring hydrogen and with the hydroxyl group Schiff bases, while in the nickel complexes with the phenyl ring hydrogen atom and with the cyclohexyl CH 2. Results of spectral analyses suggest central ions in a distorted square planar geometry with N 2O 2 chromophore group. The X-ray crystallography study confirmed tetrahedral distortion from the planarity in [Cu(II)(1 R,2 R)(−)chxn(5-methylba) 2].

Crystalline photochromism of N-salicylidene-2,6-dialkylanilines: advantage of 2,6-dialkyl substituents of aniline for preparation of photochromic Schiff base crystals.

N-(3,5-Dihalosalicylidene)-2,6-dialkylaniline derivatives were prepared and their structure and photochromic properties were investigated. From the X-ray crystallography, it was revealed that steric repulsion between the azomethine hydrogen atom and the alkyl groups at the 2,6-positions of the aniline ring lead to non-planar molecular structure, which was effective for the crystals to exhibit photochromism. The relationship between photochromicity and crystal packing of N-(3,5-dichlorosalicylidene)-2,6-dialkylanilines series was also discussed. The 2,6-dialkylaniline method was suggested to be applicable to the preparation of photochromic Schiff bases with various substituents in the salicylidene rings.

Hyperfine parameters of pyridyl-containing iminoxy radicals generated from oximes by γ-irradiation and in zeolite lattice: EPR spectroscopy and density functional study

Incorporation of pyridyl oximes into the channels of thermally activated pentasil zeolite ZSM-5 gives rise to iminoxy radicals. EPR spectrum of the species derived by dehydrogenation of di-2-pyridilketone oxime is fully anisotropic and characteristic for the iminoxy σ-type neutral radical. The EPR spectra of the radicals derived from 2-pyridinealdoxime and 4-pyridinealdoxime exhibit additional splitting due to the azomethine hydrogen. The ĝ and  tensor parameters were determined on the basis of EPR spectra. In order to identify a geometric isomer ( E or Z) of the iminoxyls obtained in the pores of the zeolite and within γ-irradiated samples of solid oximes, hyperfine interaction parameters of the generated radicals were compared with the parameters calculated using density functional theory (DFT); these calculations allow to characterize the iminoxy radical isomers formed in zeolite and oxime matrices.

A Vibrational and Theoretical Interpretation of the Conformation of Mono- and Disubstituted N-Benzylideneanilines

Abstract Infrared data for N-benzylideneanilines mono- and disubstituted predict, in agreement with CNDO molecular orbital calculations, that the internal energy transfer is induced mainly by a donor group in para position of the benzylidene ring; this effect confers to this molecular portion a prevalent planar structure. However, the charge transfer is restricted by a steric interaction between one of the ortho hydrogen atoms of the aniline ring and the azomethine hydrogen; this situation constraints this molecular portion to adopt a major non planar conformation.

Conformations of Some Monosubstituted N-Benzylideneanilines

Abstract Theoretical computations , using quantum mechanical PCILO method, have been carried out on the conformations of four monosubstituted N-benzylideneanilines—N-benzylidene-4-nitroaniline (1a), N-benzylidene-4-dimethylaminoaniline, N-(4-nitrobenzylidene)aniline, and N-(4-dimethylaminobenzylidene)aniline. The aniline ring is found to be most twisted (60°) in 1a, while in all other cases , the twist angle is 30°. The results have been compared with earlier experimental findings and rationalized in terms of two factors contributing to nonplanarity , namely , the overlapping of bridge nitrogen lone pair with the π-system of the aniline ring and a steric interaction between the azomethine hydrogen and one of the ortho hydrogens in the aniline ring.

A novel unsymmetrical quadridentate ligand 1-(2′-aminophenyl)-6-methyl-2,5-diazanona-l,6-diene-8-one and its complexes with copper(II), nickel(II) and palladium(II)

Two routes for the preparation of the title compound ( 6) have been developed. Reaction of equimolar quantities of 2-aminobenzaldehyde, pentane- 2,4-dione and 1,2-diaminoethane yields the ligand 6 and 2-methyl-3-acetylquinoline as side product. The compound 6 was obtained in high yield in a one- step condensation of 2-aminobenzaldehyde with 1-amino-4-methyl-3-azahept-4-ene-6-one ( 5). Studies on the condensation of 5 with various 2-aminobenz- aldehyde derivatives revealed that the yield of unsymmetrical ligand is evidently influenced by the acidic properties of the hydrogen atom (of atoms) of the ring substituent in the ortho position to the carbonyl group. Copper(II), nickel(II) and palladium(II) complexes of 6 have been prepared and characterized. Spectroscopic data of nickel and palladium complexes are consistent with their planar structure. A superhyperfine splitting due to nitrogen is observed in the EPR spectrum of the copper complex in spite of the presence of azomethine hydrogen atom.

Mechanistic aspects of oxidation of N‐substituted 5H‐dibenz[c,e]azepines by aldehyde oxidase

Abstract5H‐Dibenz[c,e]azepine (2) and its N‐ethyl and N‐(2‐ethoxyethyl) analogues 3 and 4 were prepared and evaluated as substrates for aldehyde oxidase. Quaternization of 2 with ethyl iodide furnished 3, while 4 was prepared by lithium aluminum hydride reduction of N‐(2‐ethoxy)ethyldiphenimide followed by mercuric acetate oxidation of the resultant amine 6. The rates of oxidation of 2 and 3 were similar, suggesting a lack of selectivity by the enzyme for the respective imine and iminium functional groups in these compounds. The rate of oxidation of 3 decreased with increasing pH while the extent of “hydration” of this substrate increased over a similar pH range, signifying a preference by the enzyme for 3 over its carbinolamine equilibrium partner. Experiments with deuterium labelled analogues of 2 and 3 indicated that azomethine hydrogen loss from these substrates during enzymatic oxidation was not rate determining. Thus 5H‐dibenz[c,e]azepine‐5,5,7‐d3 (7), prepared by lithium aluminum deuteride reduction of diphenimide (5), and its N‐ethyl analogue 8, had respective enzymatic oxidation rates which did not differ from those of their non‐deuterated counterparts.

Catalytic hydrogenation of the C=N bond 4. Hydrogenation of azomethines containing a p-dimethylamine substituent

1. A study has been made of the hydrogenation of azomethines with p-dimethylamino groups in the amine and aldehyde rings, working in ethanol solutions containing 5% Pd/C. 2. The alteration in the hydrogenation kinetic parameters under substitution is the result of p-N(CH3)2 group interaction, with the C=N bond rather than with the catalyst. 3. Although introduction of a p-dimethylamino group into the amine ring of the azomethine has little effect on the hydrogenation kinetic parameters, introduction of this same group into the aldehyde ring markedly reduce both the activation energy and the reaction rate.

Catalytic hydrogenation of C=N bond Communication 2. Hydrogenation of azomethines of p-anisylidene series

1. A study was made of the catalytic hydrogenation of the azomethines of the p-anisylidene series in the presence of 5% Pd/C in absolute ethanol at 20‡. 2. It was shown that the azomethines exhibit reversible hydrolysis equilibrium, with their subsequent regeneration on the catalyst surface. 3. The insertion of electron-donor substituents into the amino ring of the azomethines of the p-anisylidene series has little effect on the hydrogenation rate of the C=N bond. The o-OCH3 group causes a certain increase in the rate. The insertion of the p-N(CH3)2 group leads to more than a twofold decrease in the hydrogenation rate.

Catalytic hydrogenation of C=N bond Communication 1. Study of hydrogenation of azomethines of benzylidene series

1. The hydrogenolysis of benzylideneaniline, and of its methyl and methoxy derivatives, in the presence of Pd/C proceeds selectively: the hydrogenolysis of the benzyl-N bond begins only after the absorption of the first mole of hydrogen. 2. Partial hydrolysis of the C=N double bond occurs under the hydrogenation conditions due to traces of water in the solvent. 3. The insertion of electron-donor substituants into the benzene ring, attached to the nitrogen, has little effect on the hydrogenation rate of the azomethine. The o-substituted azomethines hydrogenate somewhat faster than do the m- and p-substituted derivatives.

New compounds: Preparation and hydrogenation of azomethines derived from 2, 4-dihydroxyphenyl benzyl ketones

Reaction of 2, 4-dihydroxyphenyl benzyl ketones with primary amines and subsequent catalytic hydrogenation with platinum catalyst has afforded a series of polyphenolic amines derived from resorcinol.

REACTION OF AMIDE HOMOLOGS. IX. CATALYTIC HYDROGENATION OF AZOMETHINES IN THE PRESENCE OF AMIDE AND ITS MECHANISM.

Catalytic hydrogenation of some azomethines, such as N-benzylideneaniline, N-benzylidenebenzylamine, and N- (4-methoxybenzylidene) phenethylamine in the presence of amide was examined under high pressure of hydrogen. The reaction resulted in conversion, ArCH=NR+2R'CONH2+H2→ArCHNHCOR'+RNHCOR'+NH3, particularly in excellent yields with formamide. With regard to this reaction path, it was recognized that the initiating essential reaction between azomethine and formamide would be the reaction, ArCH=NR+HCONH2→ArCH=NH+RNHCHO (NH3 acts as a catalyst), which was demonstrated by using N-benzylidene-4-sulfonamidobenzylamine as azomethine. Based on this reaction, the whole pathway for the above hydrogenation reaction was proposed. Mechanism for hydrogenation reaction of nitriles, oximes, and ammoniaaldehyde mixtures in the presence of formamide was also suggested.

Catalytic Hydrogenation of Azomethines in the Presence of Ammonia or Amines.

Catalytic Hydrogenation of Azomethines in the Presence of Ammonia or Amines.

Preparation and Hydrogenation of Azomethines Derived from 5-Aminotetrazole

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPreparation and Hydrogenation of Azomethines Derived from 5-AminotetrazoleRonald A. Henry and William G. FinneganCite this: J. Am. Chem. Soc. 1954, 76, 3, 926–928Publication Date (Print):February 1, 1954Publication History Published online1 May 2002Published inissue 1 February 1954https://doi.org/10.1021/ja01632a095RIGHTS & PERMISSIONSArticle Views175Altmetric-Citations9LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (419 KB) Get e-Alerts Get e-Alerts