Synthesis and antioxidant evaluation of some new 2-benzoylamino-5-hetaryl-1,3,4-oxadiazoles

A series of new functionalized 2-benzoylamino-5-hetaryl-1,3,4-oxadiazoles were efficiently synthesized via the reaction of the versatile key intermediates, 2-benzoylamino-5-cyanomethyl-1,3,4-oxadiazole (1) and N-(5-(5-amino-3-phenylamino)-1H-pyrazol-4-yl)-1,3,4-oxadiazol-2-yl)-benzamide (13), with some appropriate electrophilic reagents. The structures of the newly synthesized compounds were established on the basis of elemental analyses, spectral data, and by alternative synthesis wherever possible. The mechanisms of the studied reactions are discussed. Also, we evaluate the antioxidant activity of some representative examples of the newly prepared compounds. Among the synthesized compounds, 2-benzoylamino-5-cyanomethyl-1,3,4-oxadiazole (1) and N-(5-(7-methyl-5-oxo-2-(phenylamino)-4,5-dihydropyrazolo[1,5-a]pyrimidin-3-yl)-1,3,4-oxadiazol-2-yl)benzamide (17) showed excellent antioxidant activity and exhibited high protection against DNA damage induced by the Bleomycin iron complex.     

Syntheses and structures of tris(<Emphasis Type="Italic">para</Emphasis>-tolyl)-, tris(3-fluorophenyl)-, and tris(4-fluorophenyl)antimony dioximates

Tris(para-tolyl)antimony bis(2-oxybenzaldoximate) (I), tris(para-tolyl)antimony bis(2-nitrobenzaldoximate) (II), tris(para-tolyl)antimony bis(2-bromobenzaldoximate) (III), tris(3-fluorophenyl)antimony bis(2-oxybenzaldoximate) (IV), tris(4-fluorophenyl)antimony bis(2-bromobenzaldoximate) (V), and tris(4-fluorophenyl)antimony bis(2-nitrobenzaldoximate) (VI) are synthesized by the reactions of tris(paratolyl)-, tris(3-fluorophenyl)-, and tris(4-fluorophenyl)antimony with 2-oxy-, 2-nitro-, and 2-bromobenzaldoxime in diethyl ether in the presence of tert-butyl hydroperoxide. The Sb atoms in complexes I–VI have a distorted trigonal bipyramidal coordination mode with the oximate ligands in the axial positions. CIF files CCDC nos. 1062231 (I), 1059962 (II), 1465384 (III), 1465109 (IV), 1471948 (V), and 1060387 (VI).     

Synthesis,biological evaluation,and molecular docking studies of novel 1,2,3-triazole derivatives as potent anti-inflammatory agents

In the present study, a novel series of 1,2,3-triazole derivatives have been synthesized using click chemistry approach. The structures were confirmed by spectroscopic methods. The products were screened for their in vivo anti-inflammatory activity. The tested compounds 6a, 6f, 6g, 6i, 6j, 6n, and 6p, demonstrated potent anti-inflammatory activity compared to the reference drug ibuprofen. Molecular docking studies of these 1,2,3-triazole derivatives into the active site of human cyclooxygenase-2 (COX-2) (PDB code 4PH9) demonstrated good affinity for the enzyme and suggested binding properties similar to ibuprofen.     

Tris(<Emphasis Type="Italic">para</Emphasis>-tolyl)- and tris(4-fluorophenyl)antimony diaroxides: syntheses and structures

Bis(4-bromophenoxy)tris(para-tolyl)antimony (I), bis(4-nitrophenoxy)tris(para-tolyl)antimony (II), bis(4-nitrophenoxy)tris(4-fluorophenyl)antimony (III), bis(2,3,4,5,6-pentafluorophenoxy)tris(4-fluorophenyl) antimony (IV), and bis(2,3,4,5,6-pentachlorophenoxy)tris(4-fluorophenyl)antimony (V) (CIF files CCDC 1470829 (I), 1474589 (II), 1062337 (III), 1470476 (IV), and 1472954 (V)) are synthesized in high yields by the reactions of tris(para-tolyl)- and tris(4-fluorophenyl)antimony with 4-bromo-, 4-nitro-, 2,3,4,5,6-pentafluoro-, and 2,3,4,5,6-pentachlorophenol, respectively, in diethyl ether in the presence of tert-butyl hydroperoxide. The Sb atoms in compounds I–V have a distorted trigonal bipyramidal coordination with the aroxy groups in the axial positions (angles OSbO 174.08(11)°–179.4(5)°). The average Sb–C bond lengths in compounds I–V are similar and independent of the nature of the para-substituent in the aryl rings. The Sb–O distances are close to the sum of covalent radii of Sb and O atoms. Hydrogen bonds H···F are involved in the formation of the crystal structures of compounds III–V.     

Novel highly selective anion chemosensors based on 2,5-bis(2-hydroxyphenyl)-1,3,4-oxadiazole

2-(2-Hydroxyphenyl)-5-phenyl-1,3,4-oxadiazole 1 and 2,5-bis(2-hydroxyphenyl)-1,3,4-oxadiazole 2 were used as anion fluorescent and colorimetric chemosensors with high selectivity for H₂PO₄⁻ and F⁻ over Cl⁻, while 2 can even distinguish H₂PO₄⁻ from F⁻.     

Copper(II) complexes of mono-condensed N,O-donor Schiff base ligands: Synthesis,crystal structures,and antibacterial activity

Two new copper(II) complexes, [Cu(L¹)₂] (I) and [Cu(L²)₂] (II), where L¹ = 2-bromo-4-chloro- 6-(isopropyliminomethyl)phenolate and L² = 2-bromo-4-chloro-6-[(2-hydroxyethylimino)methyl]phenolate, have been prepared and structurally characterized by X-ray crystallography (CIF files CCDC nos. 1445936 (I) and 1445935 (II)). In both complexes, the Cu atoms are coordinated by two phenolate oxygen and two imino nitrogen, giving square planar geometry. The complexes have been tested on various strains of bacteria to study their antibacterial effects.     

Conformational and configurational diversity of solvent inclusion complexes of some calix[4]pyrroles and their anion recognition properties

Sterically hindered meso-tetramethyl-meso-tetraarylcalix[4]pyrroles 1-4 where aryl is p-fluorophenyl 1, p-chlorophenyl 2, and p-methylphenyl 3, 4 (configurational isomers) are synthesized and purified by the recrystallization technique. They are characterized by IR, ¹H and ¹³C NMR, and mass spectroscopy. Configurational isomers ααββ (3) and αααα (4) of meso-tetramethyl-meso-tetramethylphenylcalix[ 4]pyrroles are assigned by the ¹H NMR studies and confirmed by the X-ray diffraction analysis. The single crystal X-ray diffraction analysis reveals that the ethanol adduct of 1, the acetone adduct of 2 and 3 adopt the 1,2-conformation while the acetone-water adduct of 1 and the acetone adduct of 4 adopt partial cone and cone conformations respectively. The conformational diversity is due to non-covalent interactions among the encapsulated guest, pyrrolic NH protons, and meso- substituents. Anion binding studies (F^–, Cl^–, CH₃COO^–, HSO ₄ ^? ) are carried out through ¹H NMR titrations; the binding constants are evaluated using the EQNMR program, displaying that they are more selective towards fluoride rather than other anions with the 1:1 stoichiometry. The configuration of compounds drastically influences the ion-recognition processes.     

First example of the <Emphasis Type="Italic">anti</Emphasis>-Markownikoff addition of tellurium tetrachloride to terminal acetylene,trimethyl ethynyl silane

(μ₂-Oxo)-bis[dichloro(Z-2-chloro-1-trimethylsilylethenyl)tellurium(IV)] (III) was prepared by electrophilic addition of TeCl₄ to trimethylethynylsilane in CHCl₃ at room temperature. The reaction is the first example of the anti-Markownikoff type addition of TeCl₄ to terminal acetylenes affording as an intermediate the 1:1 adduct [Z-1-(trimethylsilyl)-2-chlorovinyl]tellurium trichloride (II). The latter is converted into III by a sequence of successive reactions of hydrolysis and dehydration. The structure of compound III was proved by the of multinuclear (¹H, ¹³C, ²⁹Si, ¹²⁵Te) NMR spectroscopy and XRD analysis. Compound III is the first example of structurally characterized C-TeCl₂-O fragment.     

Synthesis,spectroscopic and crystal structure investigation of [Cu(bzsmp)2Cl2];{bzsmp = 2-benzylsulfanyl-5-(2-methoxyphenyl)-1,3,4-oxadiazole}: cyclization of N-[bis(benzylsulfanyl)methylene]-2-methoxybenzohydrazide to 2-benzylsulfanyl-5-(2-methoxyphenyl)-1,3,4 -oxadiazole during complexation

The ligand N²-[bis(benzylsulfanyl)methylene]-2-methoxybenzohydrazide (N²-bmbh) (1) on reaction with CuCl₂.2H₂O yielded the mononuclear complex [Cu(bzsmp)₂Cl₂] (2) (2-benzylsulfanyl-5-(2-methoxyphenyl)-1,3,4-oxadiazole, bzsmp). Complex 2 has been characterized by analytical, spectroscopic and X-ray data. X-ray study of 2 reveals that the cyclized ligand 2-benzylsulfanyl-5-(2-methoxyphenyl)-1,3,4-oxadiazole (bzsmp) acts as neutral bidentate ligand to form six membered chelate ring and the presence of C–H?π (face to edge) and C–H?S and two type of C–H?Cl weak interactions.     

The preparation of dicyano-1,3,4-thiadiazole and tricyanothiazole via 1,2,3-dithiazole chemistry

Treatment of 1,2-bis(4-chloro-5H-1,2,3-dithiazol-5-ylidene)hydrazine 4 with benzyltriethylammonium iodide (1 equiv) affords dicyano-1,3,4-thiadiazole 3 and 5-cyano-1,3,4-thiadiazole-2-carboxamide 5 in 79 and 21% yields, respectively. By using polymer bound triphenylphosphine instead of benzyltriethylammonium iodide the dicyano-1,3,4-thiadiazole 3 can be isolated in 70% yield without chromatography. The reaction of DAMN with Appel salt 8 gave 2-(4-chloro-5H-1,2,3-dithiazol-5-ylideneamino)-2-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)acetonitrile 7 (14%), 2,3-bis-(4-chloro-5H-1,2,3-dithiazol-5-ylideneamino)fumaronitrile 10 (14%), and 2,3-bis(4-chloro-5H-1,2,3-dithiazol-5-ylideneamino)maleonitrile 11 (24%) together with other products. The maleonitrile 11 isomerizes into the fumaronitrile 10 on irradiation at 365 nm. Reaction of aminoacetonitrile with Appel salt 8 gives the (dithiazolylidene)acetonitrile 7 in 33% yield. Treatment of (dithiazolylidene)acetonitrile 7 with polymer bound triphenylphosphine gives tricyanothiazole 6 in 76% yield. A rational general mechanism for the transformation of bisdithiazoles to percyanoheteroles is proposed.     

Biomimetic oxidation of catechol employing complexes formed in situ with heterocyclic ligands and different copper(II) salts

In the present work, catecholase activity is presented. The complexes were prepared by condensation of the organic ligand pyrazolyl L ₁ –L ₄ and copper(II) ion in situ. The pyrazolyl compounds L ₁ –L ₄ used in this study are: L ₁ is (3,5-dimethyl-pyrazol-1-ylmethyl)-(4-methyl-pyridin-2-yl)-pyrazol-1-ylmethyl-amine; L ₂ is 1-{4-[(3,5-dimethyl-pyrazol-1-ylmethyl)-pyrazol-1-ylmethyl-amino]-phenyl}-ethanone; L ₃ is 1-{4-[(3,5-dimethyl-pyrazol-1-ylmethyl)-[1,2,4]triazol-1-ylmethyl-amino]-phenyl}-ethanone, and L ₄ is 2-[(3,5-dimethyl-pyrazol-1-ylmethyl)-[1,2,4]triazol-1-ylmethyl-amino]-6-methyl-pyrimidin-4-ol, and copper ions salts Cu(II) are (Cu(CH₃COO)₂, CuCl₂, Cu(NO₃)₂ and CuSO₄). In order to determine factors influencing the catecholase activity of these complexes, the effect of ligand nature, ligand concentration, nature of solvent and nature of counter anion has been studied. The best activity of catechol oxidation is given by the combination formed by one equivalent of ligand L ₂ and one equivalent of Cu(CH₃COO)₂ in methanol solvent which is equal to 9.09 µmol L^?1 min^?1. The Michaelis–Menten model is applied for the best combination, to obtain the kinetic parameters, and we proposed the mechanism for oxidation reaction of catecholase.     

Influence of the nature of the substituent in 3-(2-pyridyl)-1,2,4-triazole for complexation with Pd<Superscript>2+</Superscript>

The structure of four new palladium complexes [Pd(HL ² )Cl ₂ and Pd(L ^1–3 ) ₂ ] with 3-(2-pyridyl)-5-R-1,2,4-triazoles (R=H, CH₃, Ph respectively HL ¹ , HL ² , HL ³ ) was proposed based on IR, NMR, UV spectroscopy and MALDI mass spectrometry data analysis. It is found that the complexation of HL ² and HL ³ with Pd²⁺ ions results in a decrease of their fluorescence intensity and it is vice versa in case of HL ¹ . Furthermore, the influence of the substituent (R) in the 3-(2-pirydyl)-5-R-1,2,4-triazoles on the fluorescent and protolytic properties of HL ^1–3 was investigated.     

Syntheses and crystal structures of copper(II) and nickel(II) complexes derived from 2-bromo-4-chloro-6-[(2-methylaminoethylimino)methyl]phenol

A new centrosymmetric mononuclear copper(II) complex [Cu(L)₂](ClO₄)₂ (I) and a new centrosymmetric mononuclear nickel(II) complex [Ni(L)₂(MeOH)₂](ClO₄)₂ (II), where L is the zwitterionic ligand 2-bromo-4-chloro-6-[(2-methylammonioethylimino)methyl]phenolate, have been prepared from the Schiff base 2-bromo-4-chloro-6-[(2-methylaminoethylimino)methyl]phenol with copper perchlorate and nickel perchlorate, respectively. The complexes were characterized by elemental analysis, infrared spectra, and single-cyrstal X-ray diffraction (CIF files CCDC nos. 1408054 (I) and 1407973 (II)). Complex I crystallizes in the monoclinic space group P2₁/c with unit cell dimensions a = 7.7736(4), b = 21.608(1), c = 8.5194(4) Å, β = 93.907(2)°, V = 1427.7(1) ų, Z = 2, R ₁ = 0.0546, and wR ₂ = 0.1531. Complex II crystallizes in the monoclinic space group P2₁/c with unit cell dimensions a = 21.324(3), b = 16.821(2), c = 9.425(1) Å, β = 90.114(2)°, V = 3380.5(7) ų, Z = 4, R ₁ = 0.0693, and wR ₂ = 0.1627. The Cu atom in I is in square planar coordination, and the Ni atom in II is in octahedral coordination.     

Microwave assisted selective synthesis of (<Emphasis Type="Italic">E</Emphasis>)-1-(4-Chloro-7-hydroxy-2-aryl-2<Emphasis Type="Italic">H</Emphasis>-chromen-6-yl)-3-arylprop-2-en-1-ones and their antimicrobial activity

A series of new (E)-1-(4-chloro-7-hydroxy-2-aryl-2H-chromen-6-yl)-3-arylprop-2-en-1-ones (2a–2f) have been synthesized by selective mono cyclization of 4,6-dicinnamoyl resorcinols (1a–1f) using Vilsmeier–Haack reagent under conventional heating and microwave irradiation. The structures of the synthesized compounds have been elucidated by elemental analysis, IR, ¹H NMR, ¹³C NMR and Mass spectral data. The synthesized compounds were tested in vitro for antimicrobial activity.     

Design,Synthesis, and Cytotoxicity of Semisynthetic Betulinic Acid-1,2,4-Oxadiazole Amide Derivatives

Biological activity of betulinic acid derivatives containing a 1,2,4-oxadiazole ring prompted us to synthesize betulinic acid-1,2,4-oxadiazole amide derivatives 14–25 starting with the amide coupling reaction of betulinic acid 1 and (3-aryl-1,2,4-oxadiazol-5-yl)methanamines 2–13. The products were tested for cytotoxicity on three human cancer cell lines in vitro. All tested compounds demonstrated high activity. The structures of the synthesized compounds were elucidated from IR, NMR and mass spectra.     

Synthesis,crystal structure and molecular docking studies of novel 2-(4-(4-substitutedphenylsulfonyl)piperazin-1-yl)quinolone-3-carbaldehyde derivatives

The present work reports the synthesis of novel 2-(4-(4-substitutedphenylsulfonyl) piperazin-1-yl) quinolone-3-carbaldehyde derivatives, namely, 2-(4-tosylpiperazin-1-yl)quinoline-3-carbaldehyde (4a), 2-(4-(4-nitrophenylsulfonyl)piperazin-1-yl)quinoline-3-carbaldehyde (4b) and 2-(4-(4-tert-butylphenylsulfonyl) piperazin-1-yl)quinoline-3-carbaldehyde (4c). These compounds have been characterized by FT-IR, ¹H-NMR, ¹³C-NMR and LCMS. Further, the structures of compounds 4b and 4c have been elucidated by single crystal X-ray diffraction studies. The asymmetric unit of 4b contains two molecules (A and B) and that of 4c contains one. The piperazine ring in both the molecules 4b and 4c has chair conformation and the aldehyde group is twisted with respect to the quinoline group, respectively, by 13.3 (3)°, 18.2 (3)° and 11.2 (3)° in Molecule A & B of 4b and 4c due to the bulky piperazinyl group present in the ortho position. The crystal structures of both features interactions of the type C-H…O, C-H…π_aryl and π_aryl… π_aryl, leading to a three-dimensional (3D) supramolecular architecture in 4b and a one-dimensional (1D) architecture in 4c. The various intermolecular interactions exhibited in 4b and 4c are well supported by Hirshfeld surface and fingerprint plots analysis. Further, the three compounds were evaluated for their in-silico antimicrobial activity. In-silico molecular docking studies were carried out in order to know the binding modes of the synthesized compounds with DNA Gyrase A and N-myristoyltranferase as target proteins for antibacterial and antifungal docking studies, respectively.     

Synthesis,crystal structures,and antibacterial activities of Schiff base nickel(II) and cadmium(II) complexes with tridentate Schiff bases

Reaction of tridentate Schiff bases with nickel and cadmium salts in methanol afforded two new mononuclear complexes, [Ni(L¹)₂] (I) and [Cd(L²)₂] (II), where L¹ and L² are the anions of 2-bromo-4-chloro-6-[(3-dimethylaminopropylimino)methyl]phenol (HL¹) and 2-bromo-4-chloro-6-[(3-morpholin-4-ylpropylimino)methyl]phenol (HL²), respectively. The complexes were characterized by singlecrystal X-ray diffraction (CIF files CCDC nos. 1428653 (I) and 1428654 for (II)), FT-IR, and elemental analysis. Complex I crystallizes in the monoclinic space group P2 ₁/c, with a = 8.8216(8), b = 14.0424(8), c = 11.8687(12) Å, β = 111.238(2)°, V = 1370.4(2) ų, Z = 2. Complex II crystallizes in the monoclinic space group P2 ₁/n, with a = 9.6774(4), b = 15.8970(6), c = 20.3144(7) Å, β = 90.408(2)°, V = 3125.1(2) ų, Z = 4. The metal atoms in the complexes are coordinated by two tridentate Schiff base ligands, forming octahedral coordination. The free Schiff bases and the complexes were assayed for antibacterial activities. Both complexes are more active against the bacteria than the free Schiff bases. Complex II has the MIC value of 0.39 μg mL^–1 against Bacillus subtilis.     

Synthesis,characterization and extraction properties of calix[4]crown with amine units and study of its complexes with Cu(II)

In this work, we have focused on the synthesis of p-tert-butyl calix[4]crown with amine units (H ₃ L) as a class of selective receptors for metal ions. The macrocyclic ligand (H ₃ L) with N₂O₇ donors was synthesized via condensation between 1,3-diaminocalix[4]arene and 2-[3-(2-formylphenoxy)-2-hydroxypropoxy] benzaldehyde, followed by reduction of the Schiff base product in situ with sodium borohydride, then it was characterized by FT-IR, ¹H NMR and X-ray crystallography. Two Cu(II) complexes were prepared from the reaction of H ₃ L with Cu(II) salts (CuX₂, X = ClO₄ ^? and Cl^?). FT-IR, UV–Vis, elemental analysis, molar conductivity and cyclic voltammetry techniques were used for study and characterization of these complexes. On the basis of liquid–liquid extraction experiments, ligand H ₃ L indicated good affinity toward Pb²⁺ and Cu²⁺.     

Synthesis,characterization and X-ray crystal structure of novel nickel Schiff base complexes and investigation of their catalytic activity in the electrocatalytic reduction of alkyl and aryl halides

Novel potentially bidentate NO Schiff base ligands, HL ¹ and HL ² derived from condensation reaction of 2′-methoxyphenyl-2-ethylamine with salicylaldehyde (HL ¹ ) and with 2-hydroxy-4-methoxybenzaldehyde (HL ² ), and their nickel complexes were synthesized and characterized by usual spectroscopic techniques such as FT-IR, UV–Vis, ¹H NMR, ¹³C NMR and elemental analysis. It was revealed that the bidentate Schiff base ligands coordinate with Ni(II) ions yielding mononuclear complexes with 1:2 (metal/ligand) stoichiometry. This result has been determined by using X-ray crystallographic technique of HL ² and the nickel complex derived from HL ¹ (Ni(II)-2L ¹ ). So, the structural studies showed that the two Ni(II) complexes adopt a square-planar geometry around the central metal ion. Cyclic voltammetry studies were investigated in 0.1 M TBAP in DMF solution and indicate that the nickel complexes show one reduction wave related to Ni(II)/Ni(I) redox couple. The electrocatalytical properties of these complexes were also studied in the same electrolyte medium. Their electrocatalytic performances have been tested toward the electroreduction reaction of bromocyclopentane and iodobenzene, showing a promoted activity in the case of the Ni(II)-2L ² complex.     

Metalloligand-induced Synthesis of Two Cu(I)–M (M=Ni,Co) Heterobimetallic Coordination Polymers: Structures,Thermal and Luminescence Properties

Two interesting heterobimetallic coordination polymers (CPs), {[Ni(4-pytpy)₂]₂[Cu₄(N(CN)₂)₇](NO₃)(DMF)(DMSO)(H₂O)₄}_n (1) and {[Co(4-pytpy)(N(CN)₂)]₂[Cu₂(N(CN)₂)₄]}_n (2), have been synthesized based on different metalloligands [M(4-pytpy)₂]²⁺ (M=Ni 1, Co 2) (4-pytpy = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine). CPs 1 and 2 have been well characterized by elemental analysis, IR spectroscopy, thermal analysis and single-crystal X-ray diffraction. Both CPs 1 and 2 crystallize in the triclinic crystal system with the P-1 space group but feature different structures. CP 1 exhibits a unique one dimensional double-chain structure, while CP 2 possesses an infinite 2D network structure. It is interesting to note that the metalloligand [Co(4-pytpy)₂]²⁺ in CP 2 was decomposed into [Co(4-pytpy)]²⁺. Thermal analysis indicates that the chain structure of CP 1 begins to collapse after about 360 °C, while CP 2 can be stable up to 300 °C. The solid-state luminescence properties of CPs 1 and 2 have also been investigated.