Thermal properties of solid complexes with biologically important heterocyclic ligands

The stoichiometry of thermal decomposition of the complexes Co(NCS)₂(fpy)₄ (I), Co(NCS)₂(Mefpy)₄ (II) and Co(NCS)₂(bfpy)₄ (III) (where fpy = furo[3,2-c]pyridine, Mefpy = methylfuro[3,2-c]pyridine, bfpy = benzo-[2, 3]furo[3,2-c]pyridine) have been investigated in nitrogen atmosphere from room temperature (RT) to 800 °C by means of TG and DTA. The results revealed that release of heterocyclic ligands occurs in one step. Infrared data suggested that fpy, Mefpy and bfpy were coordinated to Co(II) through the nitrogen atom of the respective heterocyclic ring and anionic ligands through nitrogen atom of the NCS groups.     

Synthesis,spectroscopic properties,crystal structure and biological activities of copper(II) 2-methylthionicotinate complexes with furopyridines

The synthesis and characterization of six new 2-methylthionicotinate (2-MeSnic) copper(II) monomeric complexes [Cu(2-MeSnic)₂L₂] (L is furo[3,2-c]pyridine—fpy, 2-methylfuro[3,2-c]pyridine—Mefpy, 2,3-dimethylfuro[3,2-c]pyridine—Me₂fpy or benzo[4,5]furo[3,2-c]pyridine—Bfp), [Cu(2-MeSnic)₂(fpy)₂(H₂O)], as well as [Cu(2-MeSnic)₂(CF₃Phfpy)₂(H₂O)₂] (CF₃Phfpy is 2-(3-trifluoromethylphenyl)furo[3,2-c]pyridine) are reported. The characterizations were based on elemental analysis, infrared, electronic and EPR spectra. The crystal structure of one of the complexes has been determined. The Cu^II atoms of [Cu(2-MeSnic)₂(fpy)₂(H₂O)] are six-coordinated in a highly distorted tetragonal–bipyramidal arrangement by two nitrogen atoms, one from each fpy, in trans-positions, by three oxygen atoms of the carboxyl groups of 2-MeSnic ligands (one monodentate, one asymmetrically bidentate), one axial position being occupied by the oxygen of a water molecule. The antimicrobial effects have been tested on various strains of bacteria, yeasts and filamentous fungi. A comparison of the IC₅₀ and MIC values has shown a decrease of inhibition activities of tested compounds in the order: [Cu(2-MeSnic)₂(Bfp)₂] > Bfp > [Cu(2-MeSnic)₂(CF₃Phfpy)₂(H₂O)₂] > [Cu(2-MeSnic)₂(Me₂fpy)₂] > CF₃Phfpy > [Cu(2-MeSnic)₂(Mefpy)₂] > Me₂fpy > [Cu(2-MeSnic)₂(fpy)₂(H₂O)] > [Cu(2-MeSnic)₂(H₂O)]₂ > Mefpy > fpy = 2-MeSnicH = CuSO₄. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Furopyridines and furopyridine-Ni(II) complexes

Summary The thermal decomposition of the complexes Ni(SCN)₂(fp)₄·2H2O (I), Ni(SCN)₂(mfp)₄ (II) and Ni(SCN)₂(dmfp)₃ (III) (where fp=furo[3,2-c]pyridine, mfp=2-methylfuro[3,2-c]pyridine and dmfp=2,3-dimethylfuro[3,2-c]pyridine) have been investigated in dynamic air from room temperature to 1000°C by means of TG, DTG and DTA. The chemical composition of the complexes, solid intermediates and the resultant products of thermolysis have been identified by means of elemental analysis and complexometric titration. The results revealed that NiO was left as residue at the end of the thermal degradation experiments. IR data suggested that fp, mfp and dmfp were coordinated to Ni(II) through the N atom of the respective heterocyclic ring.     

Crystal structure, spectroscopic and magnetic properties, and antimicrobial activities of cobalt(II) 2-methylthionicotinate complexes with N-heterocyclic ligands

Synthesis and characterization of 10 new 2-methylthionicotinate (2-MeSnic) Co(II) complexes, namely, [Co(2-MeSnic)₂L₂(H₂O)₂] · nH₂O (L is N,N-diethylnicotinamide—Et₂nia, ethylnicotinate—Etnic, nicotinamide—nia, isonicotinamide—isonia, N-methylnicotinamide—N-Menia, furo[3,2-c]pyridine—fpy, 2,3-dimethylfuro[3,2-c]pyridine—Me₂fpy or benzo[4,5]furo[3,2-c]pyridine—Bfp; n is 0, 1 or 2) as well as [Co(2-MeSnic)₂L₂] (L is ronicol—ron or 2-methylfuro[3,2-c]pyridine—Mefpy), are reported. The characterizations were based on physico-chemical and spectroscopic methods. The crystal structure of one of the complexes has been determined. In the molecular complex [Co(2-MeSnic)₂(Me₂fpy)₂(H₂O)₂], the Co(II) central atom, located at a symmetry centre, is octahedrally coordinated by an oxygen atom of the unidentate 2-MeSnic carboxyl group, the nitrogen atom of the pyridine ring of Me₂fpy, a water molecule and the corresponding centrosymmetrically located atoms. Also, biological activity of the complexes against various strains of bacteria and filamentous fungi has been investigated. It is concluded that by complexation of these nicotinate derivatives their biological activities are elevated. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Condensed O-, N-heterocycles by the transformation of azidoacrylates

Summary A number of furo[3,2-c]pyridines (4a–4d) and benzo[b]derivative (4e), as well as pyrrolo[2,3-4,5]furo[3,2-c]pyridine (8) were prepared by reaction of the corresponding iminophosphoranes, available from ethyl azidoheteroacrylates and triphenylphosphine, with phenyl isocyanate. The appropriate azidoheteroacrylates were used for the preparation of some substituted furo[3,2-b:4,5-b]dipyrroles (6). The reactions of the prepared compounds are described.

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Kondensierte O-, N-Heterocyclen durch Umwandlung von Azidoacrylaten

Zusammenfassung Eine Anzahl von Furo[3,2-c]pyridinen (4a –4d), ein Benzo[b]derivat (4e) und Pyrrolo[2,3:4,5]furo[3,2-c]pyridin (8) wurden durch die Reaktion von Phenylisocyanaten mit den entsprechenden Iminophosphoranen dargestellt, die aus Ethyl-azidoheteroacrylaten und Triphenylphosphin leicht zugänglich sind. Die entsprechenden Azidoacrylate wurden zur Synthese einiger Furo[3,2-b:4,5-b]dipyrrole (6) verwendet. Die Reaktionen einiger dieser Verbindungen werden beschrieben.

     

Heterogene Reactionen fester Nickel(II)-Komplexe. XXI. Thermische Zersetzung und Stereochemie der Thiocyanato-Nickel(II)-Komplexe mit Pyridin-N-Oxid und Methylsubstituierten Pyridin-N-Oxiden

Heterogeneous Reactions of Solid Nickel(II) Complexes. XXI. Thermal Decomposition and Sterochemistry of Thiocyanato-Nickel(II) Complexes with Pyridine N-Oxide and Methylsubstituted Pyridine N-Oxides The thermal decomposition was studied for the complexes: Ni(NCS)₂(pyNO)₃ · H₂O (I), (pyNO = pyridine N-oxide), Ni(NCS)₂(2-MepyNO)₃ (II) Me = Methyl, Ni(NCS)₂(3-MepyNO)₂ · C₂H₅OH (III) and Ni(NCS)₂(4-MepyNO)₂ · H₂O (IV). On heating the solvent molecules bonded escape and then the decomposition of heterocyclic ligands sets in. The spectral and magnetic data indicate a pseudooctahedral configuration of the starting complexes as also of Ni(NCS)₂(pyNO)₃ (V), Ni(NCS)₂(3-MepyNO)₂ (VI) and Ni(NCS)₂(4-MepyNO)₂ (VII), i. e. of the initial complexes without the solvent molecules. For complexes of the type of [Ni(NCS)₂L₃] · xH₂O (L = pyNO, x = 0, 1; L = 2-MepyNO and x = 0) a dimeric structure is assumed, while for those of the type of [Ni(NCS)₂L₂] · xH₂O (C₂H₅OH) (L = 3-MepyNO and 4-MepyNO, x = 0 or 1) a polymeric structure is supposed.     

A concise synthesis of all four possible benzo[4,5]furopyridines via palladium-mediated reactions

[reaction: see text] By taking advantage of the alpha- and gamma-activation of chloropyridines as well as palladium-mediated reactions, all four possible benzo[4,5]furopyridine tricyclic heterocycles, benzo[4,5]furo[2,3-b]pyridine, benzo[4,5]furo[2,3-c]pyridine, benzo[4,5]furo[3,2-c]pyridine, and benzo[4,5]furo[3,2-b]pyridine, are efficiently synthesized from 2-chloro-3-iodopyridine, 3-chloro-4-stannylpyridine, 4-chloro-3-iodopyridine, and 2-chloro-3-hydroxypyridine, respectively.     

Two furo­pyridine complexes of nickel(II) iso­thio­cyanate

Pyridine fused with a furan ring (fupy), and its di­methyl derivative, have been used for the first time as ligands to synthesize potentially new Werner clathrates. The extended aromatic system of pyridine‐like ligands influences considerably the molecular structure of prepared nickel complexes. The molecular structure of tetrakis­(furo­[3,2‐c]­pyridine)­bis(iso­thio­cyanato)­nickel(II) tetra­hydro­furan (THF) solvate, [Ni(NCS)₂(C₇H₅NO)₄]·C₄H₈O or [Ni(NCS)₂(fupy)₄]·THF, (I), reveals a `four‐blade propeller' arrangement of ligands, with the angles between the fupy planes and the basal octahedron plane spanning the range 38.7–55.3°. These angles are much larger (69.9–78.8°) in the centrosymmetric complex tetrakis(2,3‐di­methyl­furo­[3,2‐c]­pyridine)­bis­(iso­thio­cyanato)nickel(II) 6.6‐hydrate, [Ni(NCS)₂(C₉H₉NO)₄]·6.6H₂O or [Ni(NCS)₂(Me₂fupy)₄]·6.6H₂O, (II), in which crystallographically imposed inversion symmetry is present.     

Synthesis and reactions of 2-[3-(trifluoromethyl)phenyl]furo[3,2-<Emphasis Type="Italic">c</Emphasis>]pyridine

(E)-3-{5-[3-(Trifluoromethyl)phenyl]furan-2-yl}propenoic acid (I) was prepared from 5-[3-(tri-fluoromethyl)phenyl]furan-2-carbaldehyde under the Doebner’s conditions. The obtained acid was converted to the corresponding azide II, which was cyclized by heating in diphenyl ether to 2-[3-(trifluoromethyl)phenyl]-4,5-dihydrofuro[3,2-c]pyridin-4-one (III). This compound was aromatized with phosphorus oxychloride to chloroderivative IV which was reduced with H₂NNH₂-Pd/C to the title compound V. 2-[3-(Trifluoromethyl)phenyl]furo[3,2-c]pyridin-5-oxide (VI) was synthesized by reaction of V with 3-chloroperoxybenzoic acid in dichloromethane. On treatment of VI with benzoyl chloride and potassium cyanide (Reissert-Henze reaction), corresponding 2-[3-(trifluoromethyl)phenyl]furo[3,2-c]pyridine-1-carbonitrile (VII) resulted. 5-Amino-2-[3-(trifluoromethyl)phenyl]furo[3,2-c]pyridin-5-ium-4-methylbenzene sulfonate (VIII) was prepared by direct N-amination of the title compound V with 1-[(aminooxy)sulfonyl]-4-methylbenzene in dichloromethane. Then, VIII was transformed to a non-isolated zwitterionic N-imid IX which afforded the corresponding furo[3,2-c]pyrazolo[1,5-a]pyridine carboxylic acid esters X, XI by 1,3-dipolar cycloaddition reactions with dimethyl but-2-ynedionate (DBD) or ethyl propiolate. The structures of all compounds were confirmed by their IR and NMR spectra. Presented at the 1st International Conference “Applied Natural Sciences” on the occasion of 10th anniversary of the University of St. Cyril and Methodius, Trnava, 7–9 November 2007.     

Synthesis of 2-[3-(trifluoromethyl)phenyl]furo[3,2-<Emphasis Type="Italic">c</Emphasis>]pyridine derivatives

2-[3-(Trifluoromethyl)phenyl]-4,5-dihydrofuro[3,2-c]pyridin-4-one (I) was prepared by a three-step synthesis. Its reaction with phosphorus sulfide rendered thione II which was methylated to 2-[3-(Trifluoromethyl)phenyl]-4-methylsulfanylfuro[3,2-c]pyridine (III). 5-Methyl-2-[3-(trifluoromethyl)phenyl]-4,5-dihydrofuro[3,2-c]pyridin-4-one (IV) was obtained by the reaction of I with methyl iodide in PTC conditions. The chlorine atom in derivate V was replaced with heterocyclic secondary amines via nucleophilic substitution and 4-substituted furopyridines VIa and VIb were thus prepared. 2-[3-(Trifluoromethyl)phenyl]furo[3,2-c]pyridine-4-carboxylic acid (VII) was obtained by hydrolysis of the corresponding carbonitrile Va.     

Nickel(II) and cobalt(II) coordination compounds of dichloroguanidinopyrimidines

Summary New coordination compounds of Ni^II and Co^II with dichloropyrimidinoguanidine (L) have been obtained and characterized by physico-chemical and spectroscopic methods. The complexes have the general formulae: [ML₃](ClO₄)₂, [ML₂(SO₄)], [ML₂(NCS)₂], (M = Ni or Co), [NiL₂(ClO₄)₂] and [CoL₂](ClO₄)₂. The ligands are bonded to the metal ion via one nitrogen atom from the pyrimidine heterocyclic ring and one from the guanidine group.     

The far-infrared spectra of pyridine complexes of transition metal(II) isothiocyanates

The infrared spectra (500–140 cm^?1) of the complexes [M(pyridine)_n(NCS)₂] (n = 2, M = Mn, Co, Ni, Cu, or Zn; n = 4, M = Mn, Fe, Co, or Ni) are discussed. The v/M-pyridine and v/M-NCS bands are assigned by observing the band shifts induced by isotopic labelling of the coordinated pyridine and isothiocyanate, by comparing the spectra with those of the [M(pyridine)₂Cl₂] complexes and from symmetry considerations based on their known structures. The two types of metal-ligand stretching bands occur within a rather narrow frequency range and there is evidence of some vibrational coupling between these two modes. Some earlier assignments of vM-pyridine bands require revision. The spectra of the yellow [Fe(py)₄(NCS)₂] complex and its violet oxidation product suggest that the oxidation reaction involves the transformation of trans-[Fe(py)₄(NCS)₂] into cis-[Fe(py)₃(NCS)₃]     

[1]Benzofuro[3,2-<Emphasis Type="Italic">c</Emphasis>]pyridine synthesis and coordination reactions

(E)-3-(1-Benzofuran-2-yl)propenoic acid (1) was prepared from 1-benzofuran-2-carbaldehyde under the Doebner’s conditions. The obtained acid was converted to the corresponding azide 2, which was cyclized by heating in diphenyl ether to [1]benzofuro[3,2-c]pyridine-1(2H)-one (3). This compound was aromatized with phosphorus oxychloride to chloroderivative 4 which was reduced with zinc and acetic acid to the title compound 5. [1]Benzofuro[3,2-c]pyridine-2-oxide (6) was synthesized by reaction of 5 with 3-chloroperoxybenzoic acid in dichloromethane. Treatment of 6 with benzoyl chloride and potassium cyanide (Reissert-Henze reaction) was shown to produce the corresponding [1]benzofuro[3,2-c]pyridine-1-carbonitrile (7). The title compound was used for preparation of complexes Cu₂(ac)₄(bfp)₂ (8) and CoCl₂(bfp)₂ (9), where ac=CH₃CO₂⁻ and bfp=[1]benzofuro[3,2-c]pyridine. Both oxygen atom of carboxylate ions is used in the coordination to Cu(II). Thermal properties of the complexes 8 and 9 have been studied by TG and DTA and both complexes exhibited high thermal stability while complex 9 are thermally more stable than complex 8.     

Furopyridines. III. A new synthesis of furo[3,2-b]pyridine

A convenient synthesis of furo[3,2-b]pyridine and its 2- and 3-methyl derivatives from ethyl 3-hydroxypiconate ( 1 ) is described. The hydroxy ester 1 was O-alkylated with ethyl bromoacetate or ethyl 2-bromopropionate to give the diester 2a or 2b . Cyclization of compound 2a afforded ethyl 3-hydroxyfuro[3,2-b]pyridine-2-carboxylate ( 3 ) which in turn was hydrolyzed and decarboxylated to give furo[3,2-b]pyridin-3-(2H)-one ( 4a ). Cyclization of 2b gave the 2-methyl derivative 4b . Reduction of 4a and 4b with sodium borohydride yielded the corresponding hydroxy derivative 5a and 5b respectively, which were dehydrated with phosphoric acid to give furo[3,2-b]pyridine ( 6a ) and its 2-methyl derivative ( 6b ). 2-Acetylpyridin-3-ol ( 8 ) was converted to the ethoxycarbonylmethyl ether ( 9 ) by O-alkylation with ethyl bromoacetate, which was cyclized to give 3-methylfuro[3,2-b]pyridine-2-carboxylic acid ( 10 ). Decarboxylation of 10 afforded 3-methylfuro[3,2-b]pyridine ( 11 ).     

Synthesis, Structure, Magnetism and Electrochemical Properties of Linear Pentanuclear Complex: Ni5(μ-dmpzda)4(NCS)2

吡啶修饰的线性五核金属化合物[Ni5(μ-dmpzda)4(NCS)2][ dmpzda-H2=N,N’-Di(4-methyl pyrydin-2-yl)pyrazine-2,6-diamine]被合成并表征,其电化学和磁性被报告。 化合物含有接近180º的 Ni-Ni-Ni角,末端含有两个轴配体的Ni5 线性链。这个五核线性金属链被四个顺式的dmpzda2-配体螺旋包裹。化合物中存在两种类型的Ni-Ni键长：末端连接有轴配体的Ni-Ni键长被配体影响,其键长为2.3821 Å;内部的Ni-Ni距离比较短,为2.2959 Å。两末端的Ni(II)离子由于连接轴配体构成四方锥形(NiN4NCS)并存在较长的Ni-N 键长（2.103 Å),这个键长符合高自旋Ni(II)构型。内部的三个Ni-N 距离为1.886-1.906 Å,这样构成正方形平面(NiN4)并呈低自旋的顺磁构型。化合物显示了同[Ni5(μ-tpda)4(NCS)2]类似的磁性,即在化合物中两末端Ni(II)仍存在反铁磁性的作用。     

Über Cyanatverbindungen und deren reaktives Verhalten. XXI. Reaktionsverhalten von Niob(V)- und Tantal(V)-thiocyanat gegenüber N-Donatoren

Cyanate Compounds and their Reactivity. XXI. Reactivity of Niobium(V) and Tantalum(V) Thiocyanates to N-Donators M₂(NCS)₁₀ reacts with ammonia or primary and secondary aliphatic amines to complexes of the types [M(NCS)(NH₂)₂NH]_x, [M(NCS)₃(NHR)₂ H₂NR], or [M(NCS)₃(NR′₂)₂ HNR′₂], with N-heterocyclic amines in a first step to [M(NCS)₅L]-complexes and in a further step through a redox mechanism to [M(NCS)₄L₂] complexes. [M(NCS)₅(CH₃CN)] mCH₃CN reacts with ammonia, or primary amines in acetonitrile over acetamidine and amidinolytic cleavage of M-NCS bonds to complexes of the type [M(NCS)_a(NC(NHR″)CH₃)_b(CH₃C(NH)NHR″)]_x. The prepared compounds are characterized by analytical data, derivatographic measurements, and IR or visible absorption spectra (M = Nb, Ta; x = 2; R = n-C₄H₉; R′ = C₂H₅; L = pyridine or 4-methyl-pyridine; m = 0, 1, 2; a = 1 or 4; b = 4 or 1; R″ = H, n-C₄H₉).     

Synthesis of 2-R-4,5,7-trimethyl-1-vinyl-4,5,6,7-tetrahydropyrrolo[3,2-<Emphasis Type="Italic">c</Emphasis>]pyridines

The synthesis of 1-vinyltetrahydropyrrolo[3,2-c]pyridines substituted at C₍₂₎ has been accomplished, based on 4,5,7-trimethyl-1-vinyl-4,5,6,7-tetrahydropyrrolo[3,2-c]pyridine and its 2-formyl-substituted derivative.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, 1709–1716, November, 2004.     

Reactions of 5-[3-(trifluoromethyl)-phenyl]furan-2-carbaldehyde

The Knoevenagel condensations of 5-[3-(trifluoromethyl)phenyl]furan-2-carbaldehyde with seven compounds containing an active methyl or methylene group have been studied. The compounds used were: methyl 2-cyanoacetate, malononitrile, 2-furylacetonitrile, acetophenone, 2-thioxo-1,3-thiazolidin-4-one (rhodanine), 5,5-dimethylcyclohexane-1,3-dione (dimedone), and methyl 2-azidoacetate. The effect of microwave irradiation on the condensation reactions was studied and compared with “’classical”’ conditions. Thermolysis of methyl 2-azido-3-{5-[3-(trifluoromethyl)phenyl]-2-furyl}propenoate afforded methyl 2-[3-(trifluoromethyl)phenyl)]-4H-furo[3,2-b]pyrrole-5-carboxylate. (2E)-3-{ 5-[3-(Trifluoromethyl)phenyl]-2-furyl}propenoic acid was converted to the corresponding azide, which was cyclized on heating into 2-[3-(trifluoromethyl)phenyl)]-4,5-dihydrofuro[3,2-c]pyridin-4-one. The latter after successive action of POCl₃ and NH₂NH₂-Pd/C gave 2-[3-(trifluoromethyl)-phenyl]furo[3,2-c]pyridine. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 825–831, June, 2006.     

Heteroyohimbane a noyau furannique. Nouvelle voie d'acces aux derives de la furo[3,2-c]pyrone et de la furo[3,2-c]pyridine

3,4-Dicarbomethoxyfuran bearing an acetonyl or a phenacy group in the 2 position w3as prepared by pyrolysis of the dihydrocyclo adduct from methyl acetylendicarboxylate and 2-acetonyl- or 2-phenacylfuran. Condensation of 2-acetonyl-3,4-dicarbomethoxyfuran with tryptamine gave a new heteroyohimbane with a furan ring, indolo[2,3-a]furo[3,2-c]quinolizine, a potential precursor of yohimbane. Ketodiacids from saponification allow one to obtain derivatives of the following heterocyclic ring systems, namely 4H-furo[3,2-c]pyran-4-one and furo[3,2-c]pyridine.     

Platinum(II) complexes containing 2-(alkenyl)pyridines

The ligands 2-(allyl)pyridine(APy), and 2-(1-methallyl)pyridine (1-MAPy) react with [Pt₂X₄(PEt₃)₂] (X = Cl or Br), in acetone solution to give complexes of the type [PtX(PEt₃)L] [PtX₃(PEt₃)], (L = APy or 1-MAPy), which contain a bidentate 2-(alkenyl)pyridine, whereas the same reaction in benzene solution gives trans-[PtBr₂(PEt₃)L], (L = APy or 1-MAPy), which contains a monodentate 2-(alkenyl)pyridine; ¹H NMR spectra indicate that both types of product undergo olefin exchange in solution. The same reaction with 2-(3-methallyl)-pyridine [2-(2-butenyl)pyridine] (3-MAPy), 2-(3,3-dimethylallyl)pyridine [2-(3-methyl-2-butenyl)pyridine] (3,3-DMAPy), and 2-(3-butenyl)pyridine (BPy), in either acetone or benzene solution, gives only trans-[PtBr₂(PEt₃)L]. The reaction of trans-[PtBr₂(PEt₃)L] (L = APy or 3-MAPy) with AgClO₄ gives [PtBr(PEt₃)L]ClO₄. Complexes of the type [PtCl₂L], which contain bidentate 2-(alkenyl)pyridines, result on reaction of L = APy, 3-MAPy, 3,3-DMAPy, BPy, MBPy with [Pt₂Cl₄(C₂H₄)₂].