Catechol oxidation: activity studies using electron-rich nitrogen-based ligands

We have studied the oxidation of catechol to o-quinone with atmospheric dioxygen at ambient conditions by in situ generated copper (II) complexes of five electron-rich nitrogen ligands: (3,5-dimethyl-pyrazol-1-yl)-methanol L1; 3-benzylamino-propionitrile L2; 3-[benzyl-(3,5-dimethyl-pyrazol-1-ylmethyl)-amino]-propionitrile L3; {3-[(2-cyano-ethyl)-(1,5-dimethyl-1H-pyrazol-3-ylmethyl)-amino]-propyl}-(1,5-dimethyl-1H-pyrazol-3-ylmethyl)-amino]-propionitrile L4 and 3-[{2-[(2-cyano-ethyl)-(1,5-dimethyl-1H-pyrazol-3-ylmethyl)-amino]-ethyl}-(1,5-dimethyl-1H-pyrazol-3-ylmethyl)-amino]-propionitrile L5. We found that all complexes catalyze the oxidation reaction with different rates depending on three parameters: the nature of the ligand, the nature of ion salts, and the concentration of the complex. The combination of L3(CuSO₄) gave the highest rate of this activity about 8.71 μmol¹/L¹/min¹.     

Syntheses,crystal structures and luminescence of 2,6- bis - (5-phenyl-1H-pyrazol-3-yl)pyridine and its d10 metal complexes

A new bis-pyrazole derivative, 2,6-bis-(5-phenyl-1H-pyrazol-3-yl) pyridine (H₂BPPP), and two d¹⁰ metal complexes [Zn(H₂BPPP)Cl₂](DMF)₂ (1), [Cd(H₂BPPP)Cl₂](DMF)₂ (2) have been synthesized and characterized. There is a tautomeric equilibrium of the bis-pyrazole compound in solution and the H atom of pyrazolyl NH can transfer to the adjacent N atoms. X-ray structure analyses reveal the H atom is on the 2-position of pyrazolyl ring in donor solvents, while the H atom is on the 1-position of pyrazolyl ring in metal complexes. The luminescence of the ligand and complexes have been investigated.     

Novel one-dimensional polymeric Cu(II) complexes via Cu(II)-assisted hydrolysis of the 2,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)-6-methoxy-1,3,5-triazine pincer ligand: Synthesis,structure, and antimicrobial activities

Two unexpected one-dimensional coordination polymers, [Cu(PT)(H₂O)Cl]_n 1 and [Cu₂(BPT)(ClO₄)₃(H₂O)₄]_n·2nH₂O 2 , of symmetrical triazine-based ligands were synthesized by Cu(II)-mediated hydrolysis of the 2,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)-6-methoxy-1,3,5-triazine ( MBPT ) pincer ligand. The reaction of Cu(ClO₄)₂·6H₂O with MBPT proceeded via hydrolysis of the methoxy group to produce the dicompartmental 4,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)-1,3,5-triazin-2(1H)-one ligand ( HBPT ) that then undergoes in situ complexation with Cu(II) to afford 2 . In case of CuCl₂, the reaction proceeds further with C–N cleavage of one pyrazolyl unit leading to the formation of 6-(3,5-dimethyl-1H-pyrazol-1-yl)-1,3,5-triazine-2,4(1H,3H)-dione ligand ( HPT ) that also undergoes in situ complexation with Cu(II) affording 1 . The role of Cu(II) is to increase the Lewis acid reactivity of the water molecule where similar hydrolytic reactions for MBPT were observed in acidic medium in presence of an aqueous HCl (1:1 v/v) solution. The molecular and supramolecular structures of complexes 1 and 2 were investigated using X-ray diffraction of single crystal, Hirshfeld analysis, and density functional theory calculations. The Cl…H (11.7%) and O…H (24.7%) contacts are the most important in 1 , whereas the molecular packing of 2 is controlled mainly by the O…H (58.7%) hydrogen bonds. Complex 2 showed better activity against Escherichia coli, Bacillus subtilis, and Candida albicans compared with the standard antibiotics amoxicillin, tetracycline, and ampicillin. In general, complexes 1 and 2 showed good antimicrobial activity than these antibiotics and have the advantage to be used as both antibacterial and antifungal agents.     

Synthesis,spectral, crystallography and thermal investigations of novel Schiff base complexes of manganese (III) derived from heterocyclic β-diketone with aromatic and aliphatic diamine

The Schiff base tetradentate ligands N,N-bis-(3,5-dimethyl-1-p-tolyl-1H-pyrazol-4-ylmethylene)-ethane-1,2-diamine (H₂L¹), N,N-bis-(3,5-dimethyl-1-p-sulfonyl-1H-pyrazol-4-ylmethylene)-ethane-1,2-diamine (H₂L²), N,N-bis-(3,5-dimethyl-1-p-tolyl-1H-pyrazol-4-ylmethylene)-benzene-1,2-diamine (H₂L³) and N,N-bis-(3,5-dimethyl-1-p-sulfonyl-1H-pyrazol-4-ylmethylene)-benzene-1,2-diamine (H₂L⁴) were prepared from the reaction between 5-oxo-3-methyl-1-p-tolyl-1H-pyrazole-4-carbaldehyde or 4-(4-formyl-5-oxo-3-methyl-pyrazol-1-yl)-benzenesulfonic acid and o-phenylenediamine or ethylenediamine. And these are characterized by elemental analysis, FT-IR, ¹H NMR and GC–MS. The corresponding Schiff base complexes of Mn(III) were prepared by condensation of [Mn₃(μ₃-O)(OAc)₆(H₂O)₃]·3H₂O with ligands H₂L¹, H₂L², H₂L³ and H₂L⁴. All these complexes have been characterized by elemental analysis, magnetic susceptibility, X-ray crystallography, conductometry measurement, FT-IR, electronic spectra and mass (FAB) spectrometry. Thermal behaviour of the complexes has been studied by TGA, DTA and DSC. Electronic spectra and magnetic susceptibility measurements indicate octahedral stereochemistry of manganese (III) complexes, while non-electrolytic behaviour complexes indicate the absence of counter ion.     

Trans-bis(dicyanamido)nickel(II) complexes with polyaza macrocyclic ligands

Two new trans-bis(dicyanamido)nickel(II) macrocyclic complexes, [Ni(II)(L1){N(CN)₂}₂] · H₂O (1) and [Ni(II)-(L3){N(CN)₂}₂] (2), where L1 is 3,10-bis(2-hydroxyethyl)-1,3,5,8,10,12-hexaazacyclotetradecane and L3 is 3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^1.18,0^7.12]docosane, have been synthesized and structurally characterized by spectroscopic and X-ray crystallographic methods. In (1) and (2), each central nickel(II) ion possesses a distorted octahedral geometry with four equatorial nitrogen atoms from the macrocycle and two axial nitrogen atoms from dicyanamide anions, which are terminally bonded to the central nickel atom. The solid state electronic spectra of (1) and (2) using the diffuse reflectance method show a characteristic high-spin d⁸ nickel(II) ion in a distorted octahedral environment.     

Synthesis and anticancer activity of some new heterocyclic compounds based on 1-cyanoacetyl-3,5-dimethylpyrazole

Research on Chemical Intermediates - The starting 3-(3,5-dimethyl-1H-pyrazol-1-yl)-3-oxopropanenitrile (1) reacts with phenyl isothiocyanate and ethyl bromoacetate to give the corresponding...     

1,3,2-Δ5[sgrave]5-DIAZAPHOSPHOLENES: VERSATILE REACTANTS

Abstract

In an oxidative addition reaction O,O′-bis(trimethylsilyl)diacetyldioxime 2 and triethylphosphite give 1,3,2-Δ⁵[sgrave]⁵-diazaphospholene 3a which hydrolyzes to form (Z)-2,3-bis(hydroxylamino)-2-butene 4. Benzaldehyde and 4 condensate to furnish 1,3-dihydroxy-4,5-dimethyl-2-dimethyl-4-imidazoline 5. Tris(trimethylsilyl)phosphite and 2 react to give the first tris(trimethylsiloxy)phosphorane 3b.     

Synthesis,characterization, and antioxidant activity of heterocyclic Schiff bases

Schiff base derivatives have gained great importance due to revealing a great number of biological properties. Schiff bases were synthesized by treatment of 4-amino-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one ( 1 ) with various aldehydes in methanol at reflux. In addition, diamine was reacted with an aldehyde to yield the corresponding Schiff bases. The structures of synthesized Schiff bases were elucidated by spectroscopic methods such as microanalysis, ¹H-NMR, ¹³C-NMR, and FTIR. Antioxidant activities of synthesized Schiff bases were carried out using different antioxidant assays such as 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH^•) scavenging, 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging, and reducing power activity. (E)-4-((1H-indol-3-yl)methyleneamino)-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one ( 3 ), (E)-1,5-dimethyl-4-((2-methyl-1H-indol-3-yl)methyleneamino)-2-phenyl-1H-pyrazol-3(2H)-one ( 5 ), (E)-1,5-dimethyl-2-phenyl-4-(thiophen-2-ylmethyleneamino)-1H-pyrazol-3(2H)-one ( 7 ), (E)-1,5-dimethyl-2-phenyl-4-(quinolin-2-ylmethyleneamino)-1H-pyrazol-3(2H)-one ( 9 ), (1S,2S,N1,N2)-N1,N2-bis((1H-indol-3-yl)methylene)cyclohexane-1,2-diamine ( 11 ), and (1S,2S,N1,N2)-N1,N2-bis((2-methyl-1H-indol-3-yl)methylene)cyclohexane-1,2-diamine ( 12 ) were synthesized in high yields. Compound 5 displayed a good ABTS^•+ activity. Compound 3 revealed the outstanding activity in all assays. Compound 7 has the best-reducing power ability in comparison to other synthesized compounds. Although compounds 5, 11, 12 are new, compounds 3, 7, 9 are known. Due to revealing a good antioxidant activity, the synthesized compounds ( 3, 5, 7 ) have the potential to be used as synthetic antioxidant agents.     

Synthesis of Polysubstituted Pyridopyrimidines,Pyrimidines, and Pyrazoles Based on 1,1-Bis(1H-benzotriazol-1-yl)-and 1,1-Bis(3,5-dimethyl-1H-pyrazol-1-yl)-3,4,4-trichloro-2-nitrobuta-1,3-dienes

Russian Journal of Organic Chemistry - The reaction of 3,4,4-trichloro-1,1-bis(3,5-dimethyl-1H-pyrazol-1-yl)-2-nitrobuta-1,3-diene with 2-aminopyridine gave a polysubstituted...     

Synthesis,characterization and luminescence properties of Eu(III) and Tb(III) complexes with novel pyrazole derivatives and 1,10-phenanthroline

Two novel pyrazole-derived ligands, 3-chloro-6-(3,5-dimethyl-1H-pyrazol-1-yl)picolinic acid (CDPA) and 3-chloro-6-(3,5-dimethyl-1H-pyrazol-1-yl)-N-phenylpicolinamide (CDPP) were prepared by 3,6-dichloropicolinic acid (DCPA). Their complexes with terbium(III) and europium(III) were synthesized. The complexes were characterized by elemental analysis, infrared spectra, ¹H NMR and TG–DTG. Furthermore, the above complexes using 1,10-phenanthroline as a secondary ligand were also synthesized and characterized. The luminescence properties of these complexes in solid state were investigated. The results suggested that Tb(III) complexes exhibit more efficient luminescence than Eu(III) complexes and the fluorescence of the complexes with 1,10-phenanthroline as a secondary ligand was prominently stronger than that of complexes without this ligand., and the three ligand (DCPA), (CDPP) and (CDPA) are excellent sensitizers to Eu(III) and Tb(III) ion.     

Synthesis and tautomerism of 2-(3,5-diaryl-1H-pyrazol-4-yl)-1-methyl-1H-benzimidazoles

The cyclocondensation of 1-methyl-2-phenacyl-1H-benzimidazole with aroylhydrazines yields 2-(3,5-diaryl-1H-pyrazol-4-yl)-1-methyl-1H-benzimidazoles. The ¹H NMR spectra indicate that these products display tautomerism. The more stable tautomers have structures containing electron-donor aryl substituents at C-5 and electron-withdrawing aryl substituents at C-3 of the pyrazole ring.     

Cu(II) complexes with 4,6-bis(3,5-dimethyl-1 H -pyrazole-1-yl)pyrimidine, 4-(3,5-dimethyl-1 H -pyrazole-1-yl)-6-(3,5-diphenyl-1 H -pyrazole-1-yl)pyrimidine: Synthesis and catalytic activity in ethylene polymerization reaction

The Cu(II) complexes with 4,6-bis(3,5-dimethyl-1H-pyrazole-1-yl)pyrimidine (L¹) and 4-(3,5-dimethyl-1H-pyrazole-1-yl)-6-(3,5-diphenyl-1H-pyrazole-1-yl)pyrimidine (L²) of the composition Cu₂L¹Br₄ and Cu₂L²A₄ (A = Cl, Br), respectively, were synthesized and studied by IR and magnetochemical methods. The molecular structure of the complexes is likely to be binuclear. In the presence of cocatalysts methylaluminoxane and triisobutylaluminium, the title complexes exhibit catalytic activity in the ethylene polymerization reaction. Original Russian Text ? M.B. Bushuev, V.P. Krivopalov, N.V. Semikolenova, Yu.G. Shvedenkov, L.A. Sheludyakova, G.G. Moskalenko, L.G. Lavrenova, V. A. Zakharov, S.V. Larionov, 2007, published in Koordinatsionnaya Khimiya, 2007, Vol. 33, No. 8, pp. 612–617.     

Syntheses and characterization of nickel(II), zinc(II) and palladium(II) complexes derived from three pyrazole-based polydentate ligands

Two pyrazole-based polydentate ligands, 1,3-bis(5-methyl-3-phenylpyrazol-1-yl)-propan-2-ol (Hmppzpo) and 1,3-bis(5-methyl-3-p-isopropylphenylpyrazol-1-yl)-propan-2-ol (Hmcpzpo), have been synthesized. A third ligand, 1,3-bis(3,5-dimethylpyrazol-1-yl)-propan-2-ol (Hdmpzpo), has been synthetically modified. Seven new M(II) coordination compounds of general formula M₂L₂X₂ (M?=?Zn, Ni; X?=?NO₃ or ClO₄; L?=?dmpzpo, mppzpo or mcpzpo) or MLX (M?=?Pd; L?=?dmpzpo; X?=?Cl) were synthesized and structurally characterized by elemental analysis and FT-IR analysis. The crystal structures of [Zn₂(μ-dmpzpo-O,N,N′)₂(NO₃)₂]?·?2H₂O (1?·?2H₂O), [Ni₂(μ-dmpzpo-O,N,N′)₂(CH₃CN)₂](ClO₄)₂ (2) and Pd(μ-dmpzpo-N,N′)Cl₂ (4) were determined by single-crystal X-ray crystallography. The crystal structures show that complexes 1?·?2H₂O and 2 are center-symmetric dinuclear compounds, with two metal ions bridged by two alkoxo groups and each metal ion with a distorted square-pyramidal environment. The palladium complex, 4, displayed square-planar coordination geometry around the Pd(II) ion with trans arrangement.     

Vinyl-addition polymerization of norbornene catalyzed by (pyrazol-1-ylmethyl)pyridine divalent iron, cobalt and nickel complexes

Complexes of 2-((3,5-dimethyl)-1H-pyrazol-1-ylmethyl)pyridine (L1), 2-((3,5-ditert-butyl-1H-pyrazol-1-yl)methyl)pyridine (L2), 2-((3,5-diphenyl)-1H-pyrazol-1-yl)methyl)pyridine (L3), 2-((3,5-bis(trifluoromethyl)-1H-pyrazol-1-ylmethyl)pyridine (L4) and 2,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)methyl)pyridine (L5) with cobalt(II), iron(II) and nickel(II), Ni(L1)Cl₂ (1), Co(L1)Cl₂ (2), Fe(L1)Cl₂ (3), Ni(L2)Cl₂ (4), Ni(L3)Cl₂ (5), Co(L3)Cl₂ (6), Fe(L3)Cl₂ (7), Ni(L4)Cl₂ (8) and Ni(L5)Cl₂ (9), were used as catalyst precursors to produce vinyl-addition type norbornene polymers. Both the identity of the metal center and nature of ligand affected the polymerization behaviour of the resultant catalysts. Nickel catalysts were generally more active than the corresponding iron and cobalt analogues. The polynorbornene produced have high molecular weights (0.5-2.1 × 10⁶ g/mol) and narrow molecular weight distributions. Analyses of polymer microstructure using NMR and IR spectroscopy confirmed the polymers produced to be vinyl-addition polynorbornene.     

3-取代苄氧基-6-(取代-1H-吡唑-1-基)哒嗪的合成与生物活性

3-氯-6-肼基哒嗪分别与乙酰丙酮和3-二甲胺基丙烯醛反应, 合成了中间体3-氯-6-(3,5-二甲基-1H-吡唑-1-基)哒嗪(2)和3-氯-6-(1H-吡唑-1-基)哒嗪(4), 它们与多种取代苄醇反应, 得到了一系列未见报道的3-取代苄氧基-6-(取代-1H-吡唑-1-基)哒嗪, 其结构均经1H NMR, IR和元素分析确证. 初步的生物活性测试结果表明, 所合成的化合物对油菜和稗草均具有一定的抑制作用.     

Synthesis,crystal structure and catalytic performance of bis (imino)pyridyl nickel complexes

Two new Ni(II) complexes of 2,6-bis[1-(2,6-diethylphenylimino)ethyl]pyridine (L¹), 2,6-bis[1-(4-methylphenylimino)ethyl]pyridine (L² ) have been synthesized and structurally characterized. Complex Ni(L¹)Cl₂?·?CH₃CN (1), exhibits a distorted trigonal bipyramidal geometry, whereas complex Ni(L¹)(CH₃CN)Cl₂ (2), is six-coordinate with a geometry that can best be described as distorted octahedral. The catalytic activities of complexes 1, 2, Ni{2,6-bis[1-(2,6-diisopropyl-phenylimino)ethyl]pyridine} Cl₂?·?CH₃CN (3), and Ni{2,6-bis[1-(2,6-dimethylphenylimino) ethyl]pyridine}Cl₂?·?CH₃CN (4), for ethylene polymerization were studied under activation with MAO.     

Syntheses,crystal structures and properties of two cadmium coordination polymers containing bis (2-methylimidazol-1-yl)methane(2-mBIM) and bis (imidazol-1-yl)methane (BIM) ligands

Coordination polymers, {[Cd(2-mBIM)₃](ClO₄)₂} _n (1) and [Cd(BIM)₂(NO₃)₂] _n (2), have been prepared from the reaction of bis(2-methylimidazol-1-yl)methane(2-mBIM) with Cd(ClO₄)₂ and bis(imidazol-1-yl)methane (BIM) with Cd(NO₃)₂ in ethanol and water, respectively. Their structures were characterized by single crystal X-ray diffraction and IR spectroscopy. Compound 1 crystallizes in the rhombohedral space group R-3c with a = b = 12.3617(5) Å, c = 38.896(3) Å, γ = 120°, V = 5147.5(5) ų, z = 6. The Cd^II occupies a crystallographic inversion center and is coordinated by six N atoms from six distinct 2-mBIM ligands to form a slightly distorted octahedral geometry. Each 2-mBIM is coordinated to two Cd^II cations, linking alternatively four Cd^II cations, resulting in a 32-membered M₄L₄ macrometallacycle. Compound 2 crystallizes in the monoclinic space group C2/m with a = 14.400(3) Å, b = 9.3894(18) Å, c = 8.6926(17) Å, β = 123.499(2)°, V = 980.1(3) ų, z = 2. The Cd coordinates to four nitrogen atoms from four different BIM and two nitrates to form a slightly distorted octahedral geometry. The BIM ligands bridge to form a 1-D infinite double-bridged chain structure with 16-membered M₂L₂ macrometallacyclic structural units.     

Synthesis of Some New Thiazoles and Pyrazolo[1,5-a]pyrimidines Containing an Antipyrine Moiety

Ethyl 2-{2-[4-(2,3-dimethyl-5-oxo-1-phenyl-3-(pyrazolin-4-yl)]-2-cyano-1-(phenylamino)vinylthio}-acetate, 2-[4-(2,3-dimethyl-5-oxo-1-phenyl-(3-pyrazolin-4-yl))(1,3-thiazol-2-yl)]2-(4-oxo-3-phenyl-(1,3-thiazoilidin-2-ylidene))ethanenitrile, 2-[4-(2,3-dimethyl-5-oxo-1-phenyl(3-pyrazolin-4-yl))(1,3-thiazol-2-yl)]-2-(4-methyl-3-phenyl(1,3-thiazolin-2-ylidene))ethanenitrile, 2-(5-acetyl-4-methyl-3-phenyl(1,3-thiazolin-2-ylidene))-2-[4-(2,3-dimethyl-5-oxo-1-phenyl(3-pyrazolin-4-yl))(1,3-thiazol-2-yl)]ethanenitrile, and ethyl 2-(cyano(4-(2,3-dihydro-1,5-dimethyl-3-oxo-2-phenyl-1H-pyrazol-4-yl)thiazol-2-yl)methylene)-2,3-dihydro-4-methyl-3-phenylthiazole-5-carboxylate were synthesized by treatment of 2-(4-(2,3-dihydro-1,5-dimethyl-3-oxo-2-phenyl-1H-pyrazol-4-yl)thiazol-2-yl)-3-mercapto-3-(phenylamino)-acrylonitrile with appropriate halo ketones or halo esters. Also, 4-{2-[5,7-dimethyl-2-(phenylamino)(7a-hydropyrazolo[1,5-a]pyrimidin-3-yl](1,-thiazol-4-yl)}-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one derivatives were synthesized via reaction of 4-{2-[5-amino-3-(phenylamino)pyrazolin-4-yl](1,3-thiazol-2-yl)}-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one with β-diketone or β-keto ester. All synthesized compound were established by elemental analysis, spectral data, and alternative synthesis whenever possible.     

Structure,synthesis, and voltammetric investigation of 1-(quinolin-2-yl)-2-(pyran-2-yl)ethane-1,2-dione derivatives

By the XRD analysis the structure was established of 1-(7,8-dimethyl-4-chloroquinolin-2-yl)-2-[3,5-di(tert-butyl)-6-oxo-6H-pyran-2-yl]ethane-1,2-dione formed as a result of the oxidation of 3,5-di(tert-butyl)-6-[(Z)-2-(quinolin-2-yl)-1-hydroxyethen-1-yl]pyran-2-ones. By the cyclic voltammetry the oxidation of 1-(quinolin-2-yl)-2-(pyran-2-yl)ethane-1,2-dione derivatives was shown to proceed in two stages.