Synthesis,Characterization, Antibacterial,and Antifungal Activity of Novel 2‐(2‐hydroxy‐5‐((aryl)‐diazenyl)phenyl)‐3‐(4‐hydroxyphenyl)‐thiazolidin‐4‐one

A series of novel thiazolidinones, that is, 2‐(2‐hydroxy‐5‐((aryl)‐diazenyl)phenyl)‐3‐(4‐hydroxyphenyl)‐thiazolidin‐4‐one, have been synthesized by reaction of various Schiff bases 2‐(4‐hydroxyphenylimino)methyl)‐4‐(aryl)diazenyl)phenol with ethanolic thioglycolic acid. Schiff bases were obtained by the reactions of 4‐amino phenol with 2‐hydroxy‐5‐((aryl)diazenyl)benzaldehyde. The structures of the newly synthesized compounds were confirmed by IR, ¹H NMR, mass spectra, and C, H, N elemental analysis. The thiazolidinone derivatives were evaluated for their antibacterial and antifungal activity.     

Synthesis of Novel Heterocycles Derived from 4‐Arylmethylene‐2‐phenyl‐1,3‐oxazole‐5(4H)‐ones

The acid hydrazide derivatives 2 were converted into pyrazolone, triazinone, and schiff bases. However, the reaction of Schiff base 12 with malononitrile or thioglycolic acid gives the pyrazolotriazinone or thiazolidinone derivative, respectively. The structures of the newly synthesized compounds were established on the basis of IR, ¹H‐NMR, mass spectral data, and elemental analyses. The antimicrobial activities of the synthesized compounds were examined against two types of bacteria and two types of fungi. Some of the tested compounds showed promising activities.     

The Synthesis of 2‐(Chromon‐2/3‐yl)‐3‐(5‐thione‐4‐hydro‐1,3,4‐thiadiazol‐2‐yl)‐4‐oxo‐thiazolidine

2‐Formylchromones and 3‐formylchromones as the first materials singly reacted with 2‐amino‐5‐mercapto‐1,3,4‐thiadiazole to give the corresponding Schiff bases, which on cyclocondensation with mercapto‐acetic acid in 1,4‐dioxane yielded target compounds named 4‐oxo‐thiazolidines. The structures of all the synthetic compounds were confirmed by elemental analysis and IR, ¹H NMR, LC‐MS (ESI) spectral data.     

An Efficient Approach for the Synthesis of 1,2,3‐Triazole Moiety to Generate Uracil Molecular Architectures Through Cu‐Catalyzed Azide–Alkyne Cycloaddition

A simple and efficient pathway to tether conjugates of monosaccharides or aromatic moieties to uracil establishing a 1,2,3‐triazole linker via click chemistry was reported. The reaction of arylimines of 5‐amino uracil with propargyl bromide in a basic medium gave a di‐propargylated uracil. The latter compound was converted into molecular architectures containing bis‐1,2,3‐triazole rings through Cu‐catalyzed 1,3‐cycloaddition reaction with different azides. The same arylimine of 5‐amino uracil yielded different products under reflux with propargyl bromide in acetonitril with the majority to 6‐propargylated‐5‐amino uracil.     

1H NMR,IR and UV/VIS Spectroscopic Studies of Some Schiff Bases Derived from 2‐Aminobenzothiazole and 2‐Amino‐3‐Hydroxypyridine

By condensing 2‐aminobenzothiazole with 2‐hydroxy‐1‐naphthaldehyde, 2‐hydroxybenzaldehyde, 4‐methoxybenzaldehyde, 4‐hydroxybenzal‐dehyde, benzaldehyde and 4‐dimethylaminobenzaldehyde, and five Schiff bases Ia‐Ie are prepared. Also, two Schiff bases IIa and IIb are prepared by condensation of 2‐amino‐3‐hydroxypyridine with 2‐hydroxy‐1‐naphthaldehyde and 2‐hydroxybenzaldehyde. The ¹H NMR, IR and UV/Vis spectra of these seven Schiff bases are investigated. The signals of the ¹H NMR spectra as well as the important bands in the IR spectra are considered and discussed in relation to molecular structure. The UV/Vis absorption bands in ethanol are assigned to the corresponding electronic transitions and the electronic absorption spectra of Schiff bases Ib and IIb are studied in organic solvents of different polarities. The UV/Vis absorption spectra of 2‐amino‐3‐hydroxypyridine Schiff bases IIa and IIb are investigated in buffer solutions of different pH values containing 5% (v/v) methanol, and the results are utilized for the determination of pK_a and ΔG^* of the ionization of the phenolic OH‐groups. The fluorescence spectra of IIa and IIb are studied in organic solvents of different polarities. The obtained spectral results are confirmed by some molecular calculations using the atom super position and electron delocalization molecular orbital theory for the Schiff base IIb.     

3-氨基-1H-1,2,4三唑类席夫碱的合成和生物活性

以醋酸为催化剂,用3-氨基-1H-1, 2, 4-三唑与取代苯甲醛反应合成了8个3-氨基-1H-1, 2, 4-三唑类席夫碱,化合物结构经1H NMR,IR和元素分析证实,并对其进行了生物活性测试,初步生物活性结果表明此类化合物具有良好的杀菌活性。     

Synthesis and characterization of biologically active new Schiff bases containing 3‐functionalized 1,2,4‐triazoles and their zinc(II) complexes: crystal structure of 4‐bromo‐2‐[(E)‐(1H‐1,2,4‐triazol‐3‐ylimino)‐ methyl]phenol

Biologically active triazole Schiff bases ( L ¹  L ³ ) derived from the reaction of 3‐amino‐1,2,4‐triazole with chloro‐, bromo‐ and nitro‐ substituted salicylaldehydes and their Zn(II) complexes (1–3) have been synthesized and characterized by their physical, spectral and analytical data. Triazole Schiff bases potentially act as tridentate ligands and coordinate with the Zn(II) metal atom through salicylidene‐O, azomethine‐N and triazole‐N. The complexes have the general formula [M(L‐H)₂], where M = zinc(II) and L = ( L ¹ – L ³ ), and observe an octahedral geometry. The Schiff bases and their Zn(II) complexes have been screened for in‐vitro antibacterial, antifungal and brine shrimp bioassay. The biological activity data show the Zn(II) complexes to be more potent antibacterial and antifungal than the parent simple Schiff bases. Copyright © 2011 John Wiley & Sons, Ltd.     

Design,Synthesis and Antitumor Activity of Asymmetric Bis(s‐triazole Schiff‐base)s Bearing Functionalized Side‐Chain

1‐Amino‐2‐pyrid‐3‐yl‐5‐(2‐benzoylethylthio)‐s‐triazole ( 1 ) was condensed with 1‐amino‐3‐mercapto‐5‐ [(un)substituted phenyl]‐s‐triazoles and subsequently substituted with chloroacetic acid to afford bis‐s‐triazole sulfanylacetic acid mono‐Schiff bases ( 3a – 3e ), which were condensed with 9‐formylanthracene to produce asymmetric bis(s‐triazole Schiff base) sulfanylacetic acids ( 4a – 4e ). The structures of new synthesized compounds were characterized by elemental analysis and spectral data, and their in vitro antitumor activity against L1210, CHO and HL60 cell lines was evaluted via the respective IC₅₀ values by methylthiazole trazolium (MTT) assay.     

Utilization of 2(3H)‐Furanone Bearing a Pyrazolyl Side Chain for the Construction of a Variety of Thiazolidinone Derivatives

2(3H)‐Furanone 1 was utilized for the construction of thiazolidinone derivatives. Thus, upon treatment the cyano derivatives 5 with thioglycolic acid afforded the thiazolidinone derivatives 6 . Reaction of the Schiff base derivative 9 with thioglycolic acid gave the thiazolidinone derivative 10 . Decomposition of the azides 11 in dry benzene in the presence of thioglycolic acid gave the thiazolidindione derivative 12 . Antimicrobial activities of synthesized compounds were tested. Some of the tested compounds showed promising activities.     

Synthesis,characterization, antibacterial and antifungal activity of 2‐(aryl)‐3‐(3‐((8‐hydroxyquinolin‐5‐yl)diazenyl)phenyl)thiazolidin‐4‐ones

5‐((3‐Aminophenyl)diazenyl)quinolin‐8‐ol ( 1 ) was synthesized by diazotization reaction and coupled with 8‐hydroxyquinoline moiety. This amine on facile condensation with aromatic aldehydes in presence of glacial acetic acid and ethanol affords anils ( 2 ). These anils on cyclocondensation reaction with thioglycolic acid (i.e., mercaptoacetic acid) yield the titled compound ( 3 ). The structure of the newly synthesized anils ( 2 ) and thiazolidinones ( 3 ) has been confirmed by elemental analysis and spectral analysis. The titled compounds have been screened against different bacterial and fungal strains. J. Heterocyclic Chem., (2011).     

A combinatorial chemistry approach to new materials for non‐linear optics. II. 4‐(Dimethylamino)cinnamaldehyde and a molecular complex of ­4‐­methoxycinnamaldehyde with 2,4‐­dinitroaniline

The combinatorial chemistry approach has been used to synthesize an array of Schiff bases. The structures of five of these Schiff bases have been confirmed by X‐ray analysis [Nesterov, Timofeeva, Borbulevych, Antipin & Clark (2000). Acta Cryst. C 56 , 971–975]. In two cases, the reaction conditions were not sufficient to obtain the products in question. In one case, a molecular complex, C₁₀H₁₀O₂·­C₆H₅N₃O₄, of the starting products 4‐methoxy­cinnam­aldehyde and 2,4‐di­nitro­aniline was found. X‐ray analysis revealed hydrogen‐bond formation between the mol­ecules of these reagents in the crystal. In the other case, X‐ray analysis demonstrated that no chemical reaction occurred under the reaction conditions, and only one starting reagent, 4‐(di­methyl­amino)­cinnam­aldehyde, C₁₁H₁₃NO, was found in the precipitate.     

Stereochemical aspects of the hypophosphorous acid addition to terephthalic schiff bases. Synthesis of new 1,4‐phenylene‐bis‐aminomethane‐bis‐phosphonous acids

Terephthalic Schiff bases react with hypophosphorous acid to form 1,4‐phenylene‐bis‐N‐alkyl‐aminomethanephosphonous acids in moderate yields. NMR studies demonstrated that—for several examples—this reaction led to the exclusive formation of only one diastereomeric form. NMR investigation of a chiral salt identified the meso form. In contrast hereto, a corresponding addition of hypophosphorous acid to a chiral Schiff base proved to be not stereoselective; all three possible diastereoisomers were formed in a 4:1:1 ratio. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:283–287, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20422     

Structural investigation on phenyl‐ and pyridin‐2‐ylamino(methylene)naphthalen‐2(3H)‐one. Substituent effects on the NMR chemical shifts

Schiff bases bearing phenyl and pyridyl groups were synthesized by condensation of appropriate amines with 2‐hydroxynaphthaldehyde. These Schiff bases were obtained as colored crystalline solids. The proton NMR spectra of these compounds showed a doublet for the NH protons indicating a keto tautomer for these Schiff bases. The pyridyl‐substituted Schiff bases containing hydroxyl moiety were found to show the most downfield shift for the NH protons in DMSO solvent, and this was rationalized due to the formation of a six‐ and five‐membered ring using hydrogen bonds for these two compounds. Correspondingly, the olefinic proton of the Schiff bases is also found to be a doublet due to coupling to the amine proton. These Schiff bases exhibited thermochromic properties. Detailed NMR spectral analysis for both the phenyl‐ and pyridyl‐substituted Schiff bases is presented. Copyright © 2010 John Wiley & Sons, Ltd.     

Chirale Halbsandwich‐Pentamethylcyclopentadienyl‐Rhodium(III)‐ und Iridium(III)‐Komplexe mit Schiff‐Basen aus Salicylaldehyd und α‐Aminosäureestern [1]

Chiral Half‐sandwich Pentamethylcyclopentadienyl Rhodium(III) and Iridium(III) Complexes with Schiff Bases from Salicylaldehyde and α‐Amino Acid Esters [1] A series of diastereoisomeric half‐sandwich complexes with Schiff bases from salicylaldehyde and L‐α‐amino acid esters including chiral metal atoms, [(η⁵‐C₅H₅)(Cl)M(N,O‐Schiff base)], has been obtained from chloro bridged complexes [(η⁵‐C₅Me₅)(Cl)M(μ‐Cl)]₂ (M = Rh, Ir). Abstraction of chloride from these complexes with Ag[BF₄] or Ag[SO₃CF₃] affords the highly sensitive compounds [(η⁵‐C₅Me₅)M(N,O‐Schiff base]⁺X^? (M = Rh, Ir; X = BF₄, CF₃SO₃) to which PPh₃ can be added under formation of [(η⁵‐C₅Me₅)M(PPh₃)(N,O‐Schiff base)]⁺X^?. The diastereoisomeric ratio of the complexes ( 1 ‐ 7 and 11 ‐ 12 ) has been determined from NMR spectra.     

Electrochemical transformations and evaluation of antioxidant activity of some Schiff bases containing ferrocenyl and (thio‐)phenol,catechol fragments

Electrochemical transformations and antioxidant activity of some Schiff bases 1 – 5 containing ferrocenyl group and (thio‐)phenol, catechol fragments were investigated. Compounds under investigation are: 2‐(ferrocenylmethylene)amino)phenol ( 1 ), 2‐((ferrocenylmethylene)amino)‐4,6‐di‐tert‐butylphenol ( 2 ), 2‐((ferrocenylmethylene)amino)‐thiophenol ( 3 ), 3‐((ferrocenylmethylene)hydrazonomethyl)‐4,6‐di‐tert‐butylcatechol ( 4 ) and 2‐((3,5‐di‐tert‐butyl‐4‐hydroxybenzylidene)amino)thiophenol ( 5 ). In a case of compounds 1 – 3 it has shown that the sequence of electrochemical transformations leads to the products of intramolecular cyclization – 2‐ferrocenylbenzoxazole (benzothiazole). o‐Quinone formation occurs during the electrochemical oxidation of catechol‐ferrocene 4 at the first anode stage. Electrochemical oxidation of the redox‐active fragments in Schiff bases 1–4 can be achieved indirectly at a lower potential corresponding to the oxidation of ferrocenyl moiety, consequently these substances can reveal more pronounced antioxidant properties. The antioxidant activities of the compounds were evaluated using 2,2′‐diphenyl‐1‐picrylhydrazyl radical (DPPH) assay, the reaction of 2,2′‐azobis(2‐amidinopropane hydrochloride) (AAPH) induced glutathione depletion (GSH), the oxidative damage of the DNA, the process of lipid peroxidation of rat (Wistar) brain homogenates in vitro. The compounds 1–4 in the antioxidant assays show effectiveness comparable with standard antioxidants (vitamin E, Trolox) and in some parameters superior to them. In the reaction of AAPH with the glutathione compounds 2–5 have a more pronounced protective activity than Trolox. Compounds 1–5 inhibit AAPH induced oxidation damage of the DNA. The more effective inhibitors of the lipid peroxidation process in vitro are molecules containing the bulky tert‐butyl groups: 2 and 4 and Schiff base 3 .     

Thermodynamical characteristics of the reaction of pyridoxal-5′-phosphate with L-amino acids in aqueous buffer solution

The reaction of pyridoxal-5′-phosphate with L-isomers of alanine, lysine, arginine, aspartic acid, glutamic acid, and glycine in phosphate buffer solution was studied by absorption spectroscopy and the calorimetry of dissolution at physiological acidity of the medium (pH 7.35). The formation constants of Schiff bases during reactions and changes in Gibbs energy, enthalpy, and entropy were determined. It was shown that the formation constant of the Schiff base and its spectral properties depend on the nature of the bound amino acid. The progress of the reaction with a majority of amino acids is governed by the entropy factor due to the predominant role of the dehydration effect of the reaction center of amino acids during chemical reactions. The intramolecular electrostatic interaction of an ionized phosphate group with the positively charged amino group on the end of the chain of amino acid residue stabilizes the Schiff bases formed by lysine and arginine. The extinction coefficient of the base, equilibrium constant, and the exothermic effect of the reaction then increase. The excess negative charge on the end of the chain of amino acid residues of aspartic and glutamic acids destabilizes the molecule of the Schiff base. In this case, the equilibrium constant decreases and the endothermic effect of the reaction increases.     

The Synthesis and Characterization of s‐Triazine‐Cored Tripodal Structure and Its Salen/Salophen‐Bridged Fe/Cr(III) Capped Complexes

A novel Schiff base compound was synthesized, and its complexation properties with Fe(III) and Cr(III) were investigated. Tripodal ligand was synthesized by the reaction of s‐triazine and 4‐hydroxybenzaldehyde. Then a Schiff base involving 8‐hydroxyquinoline was synthesized by the reaction of 5‐aminomethyl‐8‐hydroxyquinoline ( QN ) and 2,4,6‐tris(p‐formylphenoxy)‐1,3,5‐triazine ( TRIPOD ) in methanol/chloroform media. The obtained Schiff base ( QN-TRIPOD ) was then reacted with four trinuclear Fe(III) and Cr(III) complexes including tetradentate Schiff bases N ,N ′‐bis(salicylidene)ethylenediamine (salenH₂)/bis(salicylidene)‐o‐phenylenediamine (SalophenH₂). The synthesized ligand and complexes were characterized by means of elemental analysis carrying out ¹H NMR, FTIR spectroscopy, thermal analyses, and magnetic susceptibility measurements. Finally, metal ratios of the prepared complexes were determined by using atomic adsorption spectrometry.     

Synthetic approach for novel bis(α‐aminophosphonic acid) derivatives of chromone containing 1,2,4,3‐triazaphosphole moieties

Terephthalic acid hydrazide ( 1 ) was reacted with phenylphosphonic dichloride to yield bis(1,3,4,2‐oxadiazaphosphole) derivative 3 , which was condensed with α‐aminophosphonic acid derivative 4 to afford bis[(1,2,4,3‐triazaphospholyl)(chromonyl)methylphosphonic acid] derivative 5 . The addition of diethyl phosphite to Schiff bases 9 and 10 derived from the condensation of bis(4‐amino‐1,2,4,3‐triazaphosphole) derivative 6 or bis(4‐phosphorylamino‐1,2,4,3‐triazaphosphole) derivative 7 with 3‐formyl‐6‐methylchromone ( 8 ) yielded bis[(1,2,4,3‐triazaphospholyl)(chromonyl)aminomethylphosphonate] derivative 11 and bis[(1,2,4,3‐triazaphospholyl)(chromonyl)phosphorylamino‐methylphosphonate] derivative 12 , respectively. The structures of all products were established by elemental analysis and spectral data. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:117–122, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20520     

Direct Synthesis of Multi‐functional Pyrimidine,Pyrazine, and Pyridine Scaffolds via Inter‐ and Intramolecular Annulations of 3‐Amino‐thieno[2,3‐b]pyridine‐2‐carboxylate

The synthesis of a new series of annulated thieno[2,3‐b]pyridines was performed. Ester compound 1 underwent heterocyclization upon reaction with phenylisothiocyanate and formamide to afford pyrimidines 2 and 3 , respectively. Thienopyrimidine 5 was resulted via reaction of amino derivative 1 with triethyl orthoformate to afford the non‐isolable intermediate 4 , which allowed hydrazinolysis with hydrazine hydrate to afford the target compound. Pyrimidine type 5 was condensed with p‐nitrobenzaldehyde to afford Schiff base 6 . Refluxing of ester 1 with ethyl cyanoacetate and diethyl malonate followed by base‐mediated heterocyclization afforded condensed pyridines 8 and 9 , respectively. The tetracyclic pyrazine derivative 14 was obtained from the reaction of amino compound 1 with 2,5‐dimethoxytetrahydrofuran followed by hydrazinolysis to give carbohydrazide 11 , which undergo diazotization followed by Curtius rearrangement. The antibacterial results illustrated no significant results for the investigated compounds except compound 5 , which has moderate activity against Gram‐positive bacteria.     

Synthesis of Various Schiff Bases Containing Isoxazole Ring and Their Applications with Thioglycollic Acid and Diverse Phosphorus Reagents

A series of Schiff bases bearing isoxazole and pyrazole rings were synthesized. Application of thioglycollic acid on two selective synthesized Schiff bases afforded the corresponding thiazolidin‐4‐one derivatives. On the other hand, following the multicomponents one‐pot Kabachnik– Fields reaction, the Schiff base generated in situ from 4‐chlorobenzaldehyde and 5‐methyl isoxazol‐3‐amine was trapped by phosphorus reagents to produce the corresponding amino phosphonates in moderate yields. However, the latter products could also be obtained in better yields (≥78%) by directly applying the dialkylphosphites to a selective synthesized Schiff base. Similarly, a series of α‐aminophosphonates could be obtained from 5‐chloro‐3‐methyl‐1H‐pyrazol‐4‐carbaldehyde, 5‐methylisoxazol‐3‐amine, and phosphorus reagents. Moreover, applying hexaalkyl triamido phosphites to the N‐(4‐chlorobenzylidene)‐5‐methylisoxazol‐3‐amine in ethanol afforded methylphosphonic diamide derivatives, whereas N‐((5‐chloro‐3‐methyl‐1H‐pyrazol‐4‐yl)methylene)‐5‐methylisoxazol‐3‐amine underwent dechlorination through reaction with hexaalkyl triamido phosphites to give the respective amine derivatives.