Transfer hydrogenation via generation of hydride intermediate and base-free alcohol oxidation activity studies on designed ruthenium complexes derived from NNN pincer type ligands

Ruthenium complexes( 1 – 3 ) have been synthesized using pincer-type ligands L¹ = (E)-2-((2-phenyl-2-(pyridin-2-yl)hydrazono)methyl)pyridine, L² = (E)-2-(1-phenyl-2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)pyridine, L³ = (E)-2-(phenyl(2-phenyl-2-(pyridin-2-yl)hydrazono) methyl)pyridine. The molecular structures of all the complexes 1 , 2 and 3 were determined by using single crystal X-ray diffraction. These complexes showed excellent catalytic activities such as transfer hydrogenation and alcohol oxidation. Theoretical calculations have been performed to understand the electronic properties of all the complexes using B3LYP as a function and LANL2DZ as a basis set.     

Design,synthesis and cytotoxic activity of vitamin E bearing selenium compounds against human breast cancer cell line (MCF-7)

A new series of vitamin E/selenated pyridine, vitamin E/selenated pyridazine, vitamin E/selenated coumarine and vitamin E/selenated nicotine moieties were synthesized and their cytotoxic activity is investigated using the human breast cancer cell line. The newly synthesized compounds were characterized using spectroscopic tools (IR, ¹H NMR, ¹³C NMR, and mass spectroscopy) as well as microanalysis. Our study reveals that compound vitamin E/selenated nicotine moiety has the highest cytotoxic effect than the other synthesized compounds.     

A facile synthesis of novel 5‐substituted pyridine 2 carboxamide derivatives and their biological evaluation and 3D QSAR studies

A variety of novel 5‐substituted pyridine 2 carboxamides were designed and synthesized using both normal and solvent‐free microwave (MW) irradiation techniques. The results revealed that MW protocol proceeded smoothly under mild reaction conditions in short reaction times, thus avoiding the use of toxic organic solvents. Structural elucidation of the synthesized compounds was carried out on the basis of various spectroscopic methods, such as ¹H NMR, ¹³C NMR, LCMS, and IR. The synthesized compounds were evaluated for their in vitro antimicrobial activity (MIC) using the agar disk diffusion method. Among the various synthetic compounds, compound 3b showed higher potential activity against Escherichia coli than the other compounds. The order of activity against E. coli of the studied compounds is 3b > 3e > 3g > 3h > 3d > 3c > 3a > 3f . Additionally, 2D and 3D structural features of the synthesized derivatives were recognized by the 3D‐QSAR model. This validated model exhibited good internal (r², 0.924) and external prediction (r²pred, 0.851) correlation. The results of QSAR studies concluded that Alog P, the number of hydrogen bond acceptors, and the number of rotatable bonds were necessary features for the activity of the pyridine carboxamide derivatives.     

Survey Reactivity of Some Substituted Quinazolinones with Pentafluoro(chloro)pyridine

A new series of 4‐hetroaryl substituted quinazolines were designed and synthesized by the reaction of pentafluoro(chloro)pyridine and 2‐substituted quinazolinone. The aromatic nucleophilic substitution of pentafluoro(chloro)pyridine with quinazolinone occurs at the 4‐position of pyridine ring by the oxygen site (O‐centered nucleophile) of quinazolinone. The structures of all the compounds were confirmed by IR, ¹H NMR, ¹⁹F NMR, and ¹³C NMR spectroscopy as well as elemental analysis.     

Synthesis,spectral characterization,and biological evaluation of imidazole‐substituted pyridine‐2‐amine and benzo‐substituted imidazole‐2‐amine

A series of new imidazole‐substituted pyridine‐2‐amine and benzo‐substituted imidazol‐2‐amine 3 – 12 were synthesized by treating various amines 1(a – d) with alkyl/aryl isothiocyanate 2(a‐c) at 60–90°C in isopropyl alcohol without using any catalyst with high yields. The structures of all the newly synthesized compounds were characterized using IR, NMR (¹H, ¹³C), mass, and elemental analyses. All the newly synthesized compounds were screened for their in vitro antioxidant and antimicrobial activities to understand their biological potency. All the title compounds exhibited good antioxidant and antimicrobial activities in vitro when compared to the standard drugs.     

Synthesis and Characterization of New N‐Heterocyclic Silylazides

Three novel pyridine functionalized N‐heterocyclic silanes, bearing chloride and azide moieties, were synthesized and characterized by NMR spectroscopy (¹H, ¹³C, ²⁹Si), mass spectrometry, elemental analysis, and single‐crystal XRD. The molecular structures show a comparably strong dative interaction of the pyridine‐N with the Si center, formally inducing a penta‐coordination arrangement at the silicon(IV). Under appropriate conditions, the silylazides, presented in this work, might be able to thermo‐ or photolytically liberate gaseous nitrogen giving rise to a promising synthetic option to access a variety of new transition metal silylene complexes with potential applications in various catalytic reactions.     

Insecticidal Activity of Some New Amidophosphoric Acid Esters Containing Substituted Pyridine Moieties

Some new amidophosphoric acid esters containing substituted pyridine moieties were synthesized by the reaction of O-aryl, O-ethyl phosphoryl chlorides with 3-(aminomethyl)pyridine and 5-(aminomethyl)-2-chloropyridine. Characterization was done by ¹H NMR, ³¹P{¹H} NMR, IR, MS, and elemental analyses. The results of preliminary bioassay showed that the new compounds possess good insecticidal activity against aphides.     

Polycyclic azines. III. Synthesis of 3-aminoimidazo[1,5-a]pyridine derivatives by cyclodesulfurization of N′-Substituted-N-(2-pyridylmethyl)thioureas with dicyclohexylcarbodiimide

A series of 3-substituted aminoimidazo[1,5-a]pyridine derivatives have been synthesized by cyclodesulfurization of a variety of N′-substituted-N-(2-pyridylmethyl)thioureas with dicyclohexylcarbodiimide (DCCD). ¹H Nmr spectral analysis of all synthesized compounds is given.     

Mechanism of Host–Guest Complex Formation and Identification of Intermediates through NMR Titration and Diffusion NMR Spectroscopy

The formation of host–guest (H‐G) complexes between 1,8‐bis[(diethylgallanyl)ethynyl]anthracene (H) and the N‐heterocycles pyridine and pyrimidine (G) was studied in solution using a combination of NMR titration and diffusion NMR experiments. For the latter, diffusion coefficients of potential host–guest structures in solution were compared with those of tailor‐made reference compounds of similar shape (synthesized and characterized by NMR, HRMS, and in part XRD). Highly dynamic behavior was observed in both cases, but with different host–guest species and equilibria. With increasing concentrations of the pyridine guest, the equilibrium H₂?H₂κ¹‐G₁?HG₂ is observed (in the second step a host dimer coordinates one guest molecule); for pyrimidine the equilibrium H₂→H₁κ²‐G₁?HG₂ is observed (the formation of a 1:1 aggregate is the second step).     

Synthesis,spectroscopic characterization,and in vitro antimicrobial activity of fused pyrazolo[4′,3′:4,5]thieno[3,2-d]pyrimidine

4-Amino-3-methyl-1-phenyl-1H-thieno[2,3-c]pyrazole-5-carboxamide ( 1 ), which had been previously synthesized according to literature, was used for synthesizing pyrazolothieno-pyrimidine ( 2 ) in the presence of triethyl orthoformate and acetic acid. Chlorination of the latter compound upon reflux with phosphorus oxychloride afforded the chloropyrazolothienopyrimidine ( 3 ), which underwent heterocyclization reaction with sodium azide to produce the tetrazolo-pyrazolothienopyrimidine ( 6 ). The chloropyrimidine ( 3 ) reacted with hydrazine hydrate to give the hydrazinopyrimidine derivative ( 4 ), which in turn underwent intramolecular condensation reactions with various 1,3-dicarbonyl compounds, namely ethyl acetoacetate, ethyl benzoylacetate, ethyl cyanoacetate, acetylacetone, diethyl malonate, and ethyl (ethoxymethylene) cyanoacetate, yielding new pyrazolyl pyrazolothienopyrimidine ring systems. Also triazolopyrazolothieno-pyrimidines and benzylidene Schiff's base compounds were obtained as a result of the reactions with carbon disulfide in pyridine and benzaldehyde, respectively. The chemical structures of the newly synthesized compounds were elucidated using elemental and spectroscopic analyses (FT-IR, ¹ H-NMR, ¹³ C-NMR, and mass spectroscopy). Some of the synthesized compounds possess high antibacterial and antifungal activities.     

Design of Glycosyltransferase Inhibitors: Pyridine as a Pyrophosphate Surrogate

A series of ten glycosyltransferase inhibitors has been designed and synthesized by using pyridine as a pyrophosphate surrogate. The series was prepared by conjugation of carbohydrate, pyridine, and nucleoside building blocks by using a combination of glycosylation, the Staudinger–Vilarrasa amide‐bond formation, and azide–alkyne click chemistry. The compounds were evaluated as inhibitors of five metal‐dependent galactosyltransferases. Crystallographic analyses of three inhibitors complexed in the active site of one of the enzymes confirmed that the pyridine moiety chelates the Mn²⁺ ion causing a slight displacement (2 Å) from its original position. The carbohydrate head group occupies a different position than in the natural uridine diphosphate (UDP)–Gal substrate with little interaction with the enzyme.     

New optically active poly(amide–imide)s from N-trimellitylimido-l-amino acid and 1,2-bis[4-aminophenoxy]ethane in the main chain: Synthesis and characterization

Six new optically active poly(amide–imide)s (PAIs) with good inherent viscosities were synthesized from the direct polycondensation reaction of N-trimellitylimido-l-amino acids with 1,2-bis[4-aminophenoxy]ethane by direct polycondensation in a medium consisting of N-methyl-2-pyrrolidone (NMP)/triphenyl phosphite (TPP)/calcium chloride (CaCl₂)/pyridine (py). Diamine was synthesized by using a two-step reaction. At first 1,2-bis[4-nitrophenoxy]ethane was prepared from the reaction of two equimolars 4-nitrophenol and one equimolar 1,2-dibromo ethane and the dinitro compound was reduced by using Pd/C. Also N-trimellitylimido-l-amino acids were synthesized by the condensation reaction of trimellitic anhydride with two equimolars of various l-amino acids in acetic acid solution. The polymerization reactions produced a series of optically active PAIs with a high yield and good inherent viscosity. The resulted polymers were fully characterized by means of FTIR and ¹H NMR spectroscopy, elemental analyses, inherent viscosity, specific rotation, solubility tests, thermogravimetric analysis (TGA), and a derivative of thermogravimetric (DTG) analysis.     

Study on synthesis and characterization of novel polyimides derived from 2,6-Bis(3-aminobenzoyl) pyridine

A new kind of aromatic diamine monomer containing pyridine unit, 2,6-Bis(3-aminobenzoyl)pyridine (BABP), was synthesized by the Friedel-Crafts acylation of benzene with 2,6-pyridinedicarbonyl chloride to form 2,6-Dibenzoylpyridine (DBPY), the nitrification of DBPY with nitric acid (99%) to form dinitro compound (BNBP), and the deoxidization of BNBP using SnCl₂in ethanol, successively. The diamine monomer BABP reacted with various aromatic dianhydrides to prepare a series of poly(amic acid), meanwhile, corresponding polyimides were obtained via the thermal or chemical imidzation procedures of the resulting poly(amic acid). The poly(amic acid) solutions in N,N-dimethyacetamide (DMAc) would be coated onto a plane-glass and could be thermally converted into transparent and tough polyimides films. The compositions, structures of the resulting monomer including corresponding intermediates, as well as the structure, physical property, thermostability, thermal behavior, solubility and solution viscosity of the resulting polyimides were characterized by means of FT-IR, ¹H-NMR, ¹³C-NMR, MS (EI), DSC, TGA, wide-angle X-ray diffraction, elemental analysis methods, and the effects of reactive conditions on the above structures and properties were studied, too.     

Antibacterial,spectral and thermal aspects of some novel first transition metal‐based heterochelates

A new ligand, 5‐{[5‐(pyridine‐4‐yl)‐1,3,4‐oxadiazole‐2‐ylthio]methyl}quinoline‐8‐ol (K), was synthesized by base‐catalysed reaction of 5‐chloromethyl‐8‐hydroxy quinoline (CMQ) and 5‐(pyridine‐4‐yl)‐1,3,4‐oxadiazole‐2‐thiol. The obtained ligand K was characterized by ¹H NMR, ¹³C NMR and IR spectroscopic techniques and reacted with transition metal salts to afford metal‐containing heterochelates. The structures of the synthesized heterochelates were characterized using elemental analyses, infrared spectra, electronic spectra, magnetic measurements, FAB mass spectrum and thermogravimetric analyses. The kinetic parameters such as order of reaction (n) and the energy of activation (E_a) are reported using the Freeman–Carroll method. The pre‐exponential factor (A), the activation entropy (ΔS^#), the activation enthalpy (ΔH^#) and the free energy of activation (ΔG^#) were calculated. Heterochelates were also screened for their in vitro antibacterial activity against a range of Gram‐positive (Bacillus substilis, Staphylococcus aureus) and Gram‐negative (Escherichia coli, Serratiamarcescens) organisms. Copyright © 2010 John Wiley & Sons, Ltd.     

Stabilization of High‐Valence Ruthenium with Silicotungstate Ligands: Preparation,Structural Characterization,and Redox Studies of Ruthenium(III)‐Substituted α‐Keggin‐Type Silicotungstates with Pyridine Ligands, [SiW11O39RuIII(Py)]5−

Ruthenium(III)‐substituted α‐Keggin‐type silicotungstates with pyridine‐based ligands, [SiW₁₁O₃₉Ru^III(Py)]^5?, (Py: pyridine ( 1 ), 4‐pyridine‐carboxylic acid ( 2 ), 4,4′‐bipyridine ( 3 ), 4‐pyridine‐acetamide ( 4 ), and 4‐pyridine‐methanol ( 5 )) were prepared by reacting [SiW₁₁O₃₉Ru^III(H₂O)]^5? with the pyridine derivatives in water at 80 °C and then isolated as their hydrated cesium salts. These compounds were characterized using cyclic voltammetry (CV), UV/Vis, IR, and ¹H NMR spectroscopy, elemental analysis, titration, and X‐ray absorption near‐edge structure (XANES) analysis (Ru K‐edge and L₃‐edge). Single‐crystal X‐ray analysis of compounds 2 , 3 , and 4 revealed that Ru^III was incorporated in the α‐Keggin framework and was coordinated by pyridine derivatives through a Ru? N bond. In the solid state, compounds 2 and 3 formed a dimer through π? π interaction of the pyridine moieties, whereas they existed as monomers in solution. CV indicated that the incorporated Ru^III–Py was reversibly oxidized into the Ru^IV–Py derivative and reduced into the Ru^II–Py derivative.     

Design and Synthesis of 2,5‐Disubstituted‐1,3,4‐Oxadiazole Hybrids Bearing Pyridine and 1,2,3‐Triazole Pharmacophores

A novel series of 2,5‐disubstituted‐1,3,4‐oxadiazoles decorated with two biodynamic moieties pyridine and 1,2,3‐triazole have been successfully synthesized in good yields under mild reaction conditions. The synthesized compounds are valuable for biological activity exploration since three biodynamic moieties are covalently linked together in a single molecular framework. All the synthesized compounds were fully characterized by their detailed spectral studies IR, ¹HNMR, ¹³C NMR and Mass.     

Synthesis and mesogenic properties of four series of polyesters derived from dicarboxylic and dihydroxylic aromatic monomers

Some members of four series of polyesters were synthesized by the direct polycondensation of two types of dicarboxylic acids (4,4′-dicarboxy-α,ω-diphenoxyalkanes and 4,4′-dicarboxy-α,ω-dibenzoyloxyalkanes) with two types of bisphenols (4,4′-dihydroxy-α,ω-diphenoxyalkanes and 4,4′-dihydroxy-α,ω-dibenzoyloxyalkanes) using tosyl chloride in pyridine in the presence of N, N-dimethylformamide. The ¹H-NMR spectra of the polymers synthesized showed that these polymers have an ordenated structure. The mesogenic properties of these polymers were studied by optical microscopy and differential scanning calorimetry. Many of the polymers show nematic mesomorphism.     

一类新型酯类离子液体的合成

以氯乙酸乙酯和氮杂环化合物(1-甲基咪唑、吡啶、N-乙基哌啶、N-甲基吗啉)为原料, 采用两步法合成了一类新型的酯类离子液体, 对合成的12个化合物进行了元素分析, ¹H NMR谱和一些物理性质的测定. 大多数化合物的熔点低于100 ℃, 为室温离子液体. 所合成离子液体的热稳定范围都比较宽, 性质稳定.     

Synthesis and antimicrobial studies of new pyridine derivatives

2-(p-Acetylaminobenzenesulfonylamido)-substituted benzothiazoles were prepared from 2-amino-substituted benzothiazoles and p-acetamidobenzenesulfonyl chloride using a mixture of pyridine and Ac₂O, which formed an electrophilic N-acetyl- pyridinium complex facilitating condensation to give the desired products by removal of HCl. 2-[4-(Substituted benzothiazol-2-yl)aminosulfonylanilino]pyridine-3-carboxylic acids (synthesized from 2-chloropyridine-3-carboxylic acid and the corresponding substituted 2-(p-aminobenzenesulfonylamido)benzothiazole in 2-ethoxyethanol using Cu-powder and K₂CO₃) were then converted to acid chlorides, which on further reaction with piperazine and 4-methoxyphenylpiperazine yielded the corresponding 2-[4-(substituted benzothiazol-2-yl)amino-sulfonyl]anilino-3-(piperazinocarbonyl) pyridine and 2-[4-(substituted benzothiazol-2-yl)amino-sulfonyl]anilino-3-[(4-methoxyphenyl)piperazin-1-yl-carbonyl]pyridine. The structures of the new compounds have been established on the basis of their elemental analyses as well as IR, ¹H NMR, and mass-spectral data. All the compounds have been screened for antimicrobial activity and found to possess considerable antibacterial activity.     

N-D-labeled ionic probes for mass spectrometry

An effective ¹⁵N- and deuterium (D)-labeled 2,6-bis(oxazolin-2-yl)pyridine (pybox)-La complex based probe ionization method that produces a distinct isotopic shift was developed. The distinct isotopic shift was detected by using the newly synthesized ¹⁵N-D-labeled pybox complexes. Moreover, O-[3-(tetramethylpybox)-propyl]-hydroxylamine (oxime-TMpybox) was prepared for attachment to the carbonyl group of the target molecule. Distinct isotopic shifts and multiple charged ions were detected for various compounds having amino, thiol, carboxyl, and carbonyl groups and fullerenes, using the TMpybox ionic probe series in cold-spray ionization mass spectrometry.