Syntheses, characterization, X-ray crystal structures and emission properties of five oxovanadium(V) complexes with pyridyl/pyrimidyl-pyrazole derived ditopic ligands

Four oxovanadium(V) complexes of heterocycle based ditopic ligands PyPzOAP (N-[amino(pyridin-2-yl)methylidene]-5-methyl-1-(pyridin-2-yl)-1H-pyrazole-3-carbohydrazonic acid), PyPzOAPz (N-[amino(pyrazin-2-yl)methylidene]-5-methyl-1-(pyridin-2-yl)-1H-pyrazole-3-carbohydrazonic acid), PymPzOAP (N-[amino(pyridin-2-yl)methylidene]-1-(4,6-dimethylpyrimidin-2-yl)-5-methyl-1H-pyrazole-3-carbohydrazonic acid) and PyPzCAP (5-methyl-1-(pyridin-2-yl)-N′-[1-(pyridin-2-yl)ethylidene]-1H-pyrazole-3-carbohydrazide) and a binuclear (di-μ-oxo) oxovanadium(V) complex of the ligand PymPzCAP (1-(4,6-dimethylpyrimidin-2-yl)-5-methyl-N′-[1-(pyridin-2-yl)ethylidene]-1H-pyrazole-3-carbohydrazide) have been investigated. The ligands act as uninegative NNO tridentates donors for the VO₂⁺ ion exhibiting their monotopicity. The ligands show varying emission properties due to the presence of fluophoric groups like 1-(2-pyridyl)pyrazole or 1-(2-pyrimidyl)pyrazole. The vanadium(V) complexes show fluorescence quenching with respect to the used ligands to a varying extent. The complexes were characterized by UV-Vis, IR, cyclic voltammetry and X-ray crystallography.     

Modification of biologically active amides and amines by fluoro-containing heterocycles 10. γ-Carbolines modified by 2-trifluoromethylimidazo-[1,2-a]pyridin-3-ylpropionamide fragments

An approach to the modification of biologically active γ-carbolines by the 2-trifluoromethylimidazo[1,2-a]pyridin-3-ylpropionamide fragments was suggested, which consisted of the reaction of N-methyl-N-(2-trifluoromethylimidazo[1,2-a]pyridin-3-yl)prop-2-enamides with γ-carbolines in the presence of catalytic amounts of cesium fluoride. Method of radioligand binding was used to study effects of the synthesized 3-(1,2,3,4-tetrahydro-5H-pyrido[4,3-b]-indol-5-yl)-N-methyl-N-[2-(trifluoromethyl)imidazo-[1,2-a]pyridin-3-yl]propanamides on the neuronal NMDA-receptors.     

Synthesis,characterization, and immobilization of nickel(II) tetradentate Schiff-base complexes on clay as heterogeneous catalysts for the oxidation of cyclooctene

Nickel(II) tetradentate Schiff-base complexes of N,N′-(bis(pyridin-2-yl)formylidene)ethane-1,2-diamine (L1), N,N′-(bis(pyridin-2-yl)formylidene)cyclohexane-1,2-diamine (L2), N,N′-(bis(pyridin-2-yl)formylidene)benzene-1,2-diamine (L3), N,N′-(bis(pyridin-2-yl)formylidene)meso-stilben-1,2-diamine (L4), and N,N′-(bis(pyridin-2-yl)formylidene)propane-1,3-diamine (L5) were synthesized, characterized, and immobilized on sodium montmorillonite. The complexes were characterized by IR spectroscopy, diffuse reflectance spectra (DRS), and atomic absorption spectroscopy (AAS). IR and DRS data of the heterogeneous catalysts show that the Ni(II) complexes were physically entrapped within the sodium montmorillonite clay. The supported complexes show good catalytic activity for the epoxidation of cyclooctene using tert-butylhydroperoxide (TBHP) as oxygen source in acetonitrile. The Ni-catalyzed oxidation proceeds with 62.3% selectivity for epoxidation with 69% conversion for supported [Ni(L5)].     

Reactions of 2-hydroxy-5-(1-adamantyl)benzene-1,3-dicarbaldehyde with ethane-1,2-diamine, trans-cyclohexane-1,2-diamine, and N-(2-aminoethyl)ethane-1,2-diamine

Reactions of 2-hydroxy-5-(1-admantyl)benzene-1,3-dicarbaldehyde with ethane-1,2-diamine, transcyclohexane-1,2-diamine, and N-(2-aminoethyl)ethane-1,2-diamine were studied in strongly dilute solution and under conditions of template synthesis in the presence of H₃BO₃. The effects of reaction conditions and initial diamine structure on the cyclocondensation process were determined. Selective [3 + 3]-cyclocondensation of 2-hydroxy-5-(1-admantyl)benzene-1,3-dicarbaldehyde with trans-cyclohexane-1,2-diamine and [2 + 2]-cyclization with N-(2-aminoethyl)ethane-1,2-diamine were performed in chloroform in the presence of H₃BO₃. The first representative of adamantylcalixsalens was synthesized.     

Synthesis of azinoazole structural isomers by photocyclization

Irradiation of 2-chloro-N-(pyridin-2-yl)pyridin-3-amine and N-(2-chloropyridin-3-yl)-4,6-dimethyl-pyrimidin-2-amine in aqueous-alcoholic solution gave new azinoazole derivatives, 6-chlorodipyrido-[1,2-a:5′,4′-d]imidazole and 1,3-dimethylpyrido[3′,2′:4,5]imidazo[1,2-a]pyrimidine, respectively.     

Synthesis, crystal structure and antibacterial activity of a group of mononuclear manganese(II) Schiff base complexes

Five mononuclear complexes of manganese(II) of a group of the general formula, [MnL(NCS)₂] where the Schiff base L = N,N′-bis[(pyridin-2-yl)ethylidene]ethane-1,2-diamine (L¹), (1); N,N′-bis[(pyridin-2-yl)benzylidene]ethane-1,2-diamine (L²), (2); N,N′-bis[(pyridin-2-yl)methylidene]propane-1,2-diamine (L³), (3); N,N′-bis[(pyridin-2-yl)ethylidene]propane-1,2-diamine (L⁴), (4) and N,N′-bis[(pyridin-2-yl)benzylidene]propane-1,2-diamine (L⁵), (5) have been prepared. The syntheses have been achieved by reacting manganese chloride with the corresponding tetradentate Schiff bases in presence of thiocyanate in the molar ratio of 1:1:2. The complexes have been characterized by IR spectroscopy, elemental analysis and other physicochemical studies, including crystal structure determination of 1, 2 and 4. Structural studies reveal that the complexes 1, 2 and 4 adopt highly distorted octahedral geometry. The antibacterial activity of all the complexes and their respective Schiff bases has been tested against Gram(+) and Gram(−) bacteria.     

Coordination compounds of cobalt,nickel, copper,and zinc with N 1,N 2-bis(pyridin-2-ylmethylidene)benzene-1,2-diamine and its derivatives

o-Phenylenediamine reacts with 2-formyl-, 2-acetyl-, or 2-benzoylpyridine in ethanol in the presence of cobalt, nickel, copper, or zinc chlorides to form monomeric complexes ML^1–3Cl₂·nH₂O {M = Co, Ni, Cu, Zn; L¹ = N ¹,N ²-bis(pyridin-2-ymethylidene)benzene-1,2-diamine, L² = N ¹,N ²-bis(pyridin-2-ylethylidene) benzene-1,2-diamine, L³ = N ¹,N ²-bis[phenyl(pyridin-2-yl)methylidene]benzene-1,2-diamine; n = 0–3}. The condensation products (L¹–L³) act in the complexes as tetradentate N,N,N,N-ligands. Thermolysis of the complexes occurs in two stages: dehydration (70–95°C) and complete degradation (320–450°C). At concentrations of 10^?5–10^?7 M, the complexes inhibit in vitro growth and proliferation of HL-60 human promyelocytic leukemia cells.     

New general synthesis of benzo[4,5]imidazo[1,2-<Emphasis Type="Italic">a</Emphasis>]pyrimidine and benzo[4,5]imidazo[2,1-<Emphasis Type="Italic">b</Emphasis>]quinazoline derivatives

The reactions of benzene-1,2-diamine with 5-substituted 2-(alkylsulfanyl)-4-methylpyrimidin-6(1H)-ones and 2-(propylsulfanyl)- and 5-iodo-2-(propylsulfanyl)-3,4-dihydroquinazolines at 175–185°C under solvent-free conditions unexpectedly afforded benzo[4,5]imidazo[1,2-a]pyrimidine, benzo[4,5]imidazo[2,1-b]-quinazoline, and 2,2′-(benzene-1,2-diyldiimino)bis[pyrimidin-4(3H)-ones]. The described reaction is the first example of synthesis of these heterocyclic systems by fusion of benzimidazole to pyrimidine or quinazoline and is likely to follow ANRORC mechanism.     

The formation of 'classical' and 'half unit' Schiff-base ligands from their components on a molybdenum(IV) centre

The in situ synthesis of the complex, (PPh₄)[Mo(CN)₃O(aceen)] (aceen = N-[1-(pyridin-2-yl)ethylidene]ethane-1,2-diamine), with a 'half unit' Schiff base ligand (with a free amino group) is described and compared with that of [Mo(CN)₂O(diaceen)]·H₂O (diaceen = N,N-bis[1-(pyridin-2-yl)ethylidene]ethane-1,2-diamine) in which a 'classical', tetradentate Schiff base ligand is formed. The mechanism of the 'half unit' and 'classical' template Schiff bases ligand formation is discussed.     

Synthesis of 1-(1,3-dialkyl-2-oxo-2,3-dihydro-1<Emphasis Type="Italic">H</Emphasis>-imidazo-[4,5-<Emphasis Type="Italic">b</Emphasis>]pyridin-5-yl)-5-oxopyrrolidine-3-carboxylic acids

Nitration of 2,3-dihydro-1H-imidazo[4,5-b]pyridin-2-one gave its 5-nitro derivative which was subjected to alkylation with dimethyl sulfate, diethyl sulfate, and benzyl(dimethyl)phenylammonium chloride. The resulting 1,3-dimethyl-, 1,3-diethyl-, and 1,3-dibenzyl-5-nitro-2,3-dihydro-1H-imidazo[4,5-b]pyridin-2-ones were reduced to the corresponding 1,3-dialkyl-5-amino-2,3-dihydro-1H-imidazo[4,5-b]pyridin-2-ones, and the latter reacted with itaconic acid to produce 1-(1,3-dialkyl-2-oxo-2,3-dihydro-1H-imidazo[4,5-b]pyridin-5-yl)-5-oxopyrrolidine-3-carboxylic acids. 1-(2-Oxo-2,3-dihydro-1H-imidazo[4,5-b]pyridin-5-yl)-5-oxopyrrolidine-3-carboxylic acid was obtained by analogous reaction with 5-amino-2,3-dihydro-1H-imidazo[4,5-b]-pyridin-2-one.     

New heterocyclic structures. [1,2,5]Thiadiazolo[3′,4′:4,5]pyrimido-[2,1-b][1,3]thiazine and thiazolo[3,2a][1,2,5]thiadiazolo[3,4-d]pyrimidine

Derivatives of two new molecular structures, namely, 7,8-dihydro-6H,10H-[1,2,5]thiadiazolo[3′,4′:4,5]pyrimido[2,1-b][1,3]thiazin-10-one and 6,7-dihydro-9H-thiazolo[3,2-a][1,2,5]thiadiazolo[3,4-d][pyrimidin-9-one, and derivatives of N-substituted sulfamic acid, namely, (8-amino-3,4-dihydro-2H,6H-pyrimido[2,1-b][1,3]thiazin-6-on-7-yl)sulfamic acid and (7-amino-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidin-5-on-6-yl)sulfamic acid, were separated out as by-products in the reduction reaction of 8-amino-3,4-dihydro-7-nitroso-2H,6H-pyrimido[2,1- b][1,3]thiazin-6-one and 7-amino-2,3-dihydro-6-nitroso-5H-thiazolo[3,2-a]pyrimidin-5-one derivatives, respectively, with sodium hydrosulfite. A mechanism of reaction, which hypothesizes the action of sodium hydrosulfite in an asymmetic form, is proposed. The results of single-crystal X-ray investigation on 7,8-dihydro-6H,10H-[1,2,5]thiadiazolo[3′,4′:4,5]pyrimido[2,1-b][1,3]thiazin-10-one (R = 0.032 for 863 reflections) and (8-amino-3,4-dihydro-2H,6H-pyrimido[2,1-b]- [1,3]thiazin-6-on-7-yl)sulfamic acid, sodium salt (R = 0.028 for 3507 reflections) are reported.     

Synthesis of benzimidazole derivatives via reaction between aromatic amines and aldehydes: Structure determination and theoretical insights

The condensation reaction between primary amine and aromatic aldehyde or ketone ubiquitously synthesizes –C=N- function that appears in the Schiff bases. Presence of ortho –NH/NH₂ group may form a cyclic product which is further oxidized to generate –C=N- function. Herein, two quinoline based cyclic benzimidazole compounds, namely, 2-[1-(Phenyl-pyridin-2-yl-methyl)-1H-benzoimidazol-2-yl]-quinoline (L5) and 2-[1-(Phenyl-pyridin-2-yl-methyl)-1H-benzoimidazol-2-yl]-quinolin-8-ol (L6) are synthesized from o-phenylenediamine derivative [N¹-(phenyl(pyridin-2-yl)methyl)benzene-1,2-diamine] (L) via condensation followed by in-situ dehydrogenation. The structures of the products have been confirmed by the single crystal X-ray diffraction measurement and other physicochemical data. The intra- and intermolecular H-bonding, C–H ^… π interactions in the structures instigate supramolecular self-assembly. The DFT computation has been attempted to explain the formation of energy minimized cyclic product out of acyclic counterpart; the meticulous comparison of the present theoretical outcomes with that of previously reported o-phenylenediamine derivatives, further supports the formation of energy minimized products.     

Stereoselective pyrroline-ring formation through the cyclization of conjugated azomethine ylides at the periphery of pyrido[1,2-a]pyrimidine system

The thermal reaction of N-benzyl-N-[3-(N-substituted imino)methyl-4-oxo-4H-pyrido[1,2-a]pyrimidin-2-yl]amino acid esters, generated from aldehyde esters and primary amines, provides 2,3-dihydropyrido[1,2-a]pyrrolo[2,3-d]pyrimidin-4(1H)-one derivatives effectively and stereoselectively. Therein, the stereoselective generation of conjugated azomethine ylides from the imine esters and their cyclization is essential for the pyrroline-ring formation.     

Synthesis of 7-iodo(arylsulfanyl)methyl-7,8-dihydro-[1,3]thiazolo[2,3-i]purinium pentaiodide (perchlorates) and their transformation into 4-amino-5-(1,3-thiazol-2-yl)imidazole derivatives

Intramolecular electrophilic cyclization of 6-allylsulfanylpurine by the action of iodine and arenesulfenyl chlorides gave 7-iodomethyl-7,8-dihydro[1,3]thiazolo[2,3-i]purin-6-ium pentaiodide and 7-arylsulfanylmethyl-7,8-dihydro[1,3]thiazolo[2,3-i]purin-6-ium perchlorates, respectively. 7-Iodomethyl-7,8-dihydro-[1,3]thiazolo[2,3-i]purin-6-ium iodide reacted with sodium and potassium alkoxides to produce alkyl N-[5-(4-methyl-1,3-thiazol-2-yl)-1H-imidazol-4-yl]formimidates, and its reaction with secondary cyclic amines afforded 5-(4-methyl-1,3-thiazol-2-yl)-N-[morpholin-4-yl(or piperidin-1-yl)methylidene]-1H-imidazol-4-amines. Successive treatment of 7-arylsulfanylmethyl-7,8-dihydro[1,3]thiazolo[2,3-i]purin-6-ium perchlorates with sodium acetate and morpholine led to the formation of 5-(4-arylsulfanylmethyl-4,5-dihydro-1,3-thiazol-2-yl)-N-(morpholin-4-ylmethylidene)-1H-imidazol-4-amines.     

Synthesis of bis(arylcarbonylamino-1H-benzimidazol-5-yl) ethers

A procedure has been developed for the synthesis of bis(arylcarbonylamino-1H-benzimidazol-5-yl) ethers by reaction of the corresponding substituted benzoyl chloride with sodium cyanamide, followed by treatment of the resulting N-cyanobenzamide with 4-(3,4-diaminophenoxy)benzene-1,2-diamine in acid medium.     

Thiocyanation of N-arenesulfonyl-N′-aroyl-1,4-benzoquinone diimines

The reaction of N-arenesulfonyl-N′-aroyl-1,4-benzoquinone diimines with potassium thiocyanate in glacial acetic acid occurs as 1,4-addition of thiocyanate ion by the sulfur atom to the quinoid ring in the meta position with respect to the aroyl group. The addition products, N-[4-(arenesulfonamido)-3-thiocyanatophenyl]-benzamides, partially undergo intramolecular cyclization to N-(2-imino-3-arenesulfonyl-2,3-dihydro-1,3-benzothiazol-6-yl)benzamides whose hydrolysis yields 2-amino-6-benzamido-1,3-benzothiazol-3-ium arenesulfonates. The latter lose arenesulfonic acid with formation of N-(2-amino-1,3-benzothiazol-6-yl)benzamides on treatment with a mixture of methanol with water and acetic acid.     

Synthesis of N,N′-bis[4-(1H-1,2,3-triazol-1-yl)furazan-3-yl]-methylenediamine derivatives

[3+2] Cycloaddition of azide groups of N,N′-bis(4-azidofurazan-3-yl)methylenediamine to 1,3-dicarbonyl compounds and malonodinitrile was shown to proceed regioselectively with the formation of the corresponding N,N′-bis[4-(1H-1,2,3-triazol-1-yl)furazan-3-yl]methylenediamine derivatives. The reactions of N,N′-bis(4-azidofurazan-3-yl)methylenediamine with cyanoacetic acid ethyl ester and amide led to the formation of the product of transformation of the azide group in the starting compound to the amino groups.     

A NOVEL SYNTHESIS OF 2-SUBSTITUTED-4H-THIENO [2,3-d][1,3] OXAZIN-4-ONE AND 2,3-DISUBSTITUTED THIENO [2,3-d]PYRIMIDIN-4(3H)-ONE DERIVATIVES

Abstract

The synthesis of acetic 2-{[1-methyl-2-(4-oxo-5,6,7,8-tetrahydro-4H-benzo [4,5]-thieno [2,3-d] [1,3-oxazin-2-yl)ethylidene]amino}-4,5,6,7-tetrahydrohenzo[b]thiophene ?3-carboxylic acid anhydride 5 and 2-(oxopropyl)-5,6,7,8-tetrahydro-4H-benzo-[4,5] thieno[2,3-d][1,3]oxazin-4-one 7, has been achieved in three steps from ethyl 2-amino-4,5,6,7-tetrahydrobenzo(b]thiophene-3-carboxlate 1 via the reaction with ethyl acetoacetate followed by hydrolysis and acetic anhydride-induced cyclization. The 2-substituent in compound 5 has two functional groups i.e. active methylene and acid anhydride which are suitably located for intramolecular transformation. Thermal and/or base catalyzed intramolecular cyclization of 5 afforded 2-(4-acetoxy-(hydroxyl)-2-methyl-5,6,7,8-tetrahydrobenzo[4,5] thieno[2,3-b]pyridin-3-yl)-5,6,7,8- tetrahydro-4H-benzo[4,5]thieno[2,3-d] [1,3]oxazin-4-one 10 and 9 respectively. Treatment of 5 with hydrazine hydrate, aromatic and/or heterocyclic amines induced the same intramolecular cyclization with a concomitant oxazine-pyrimidine interconversion to give 3-amino(aryl or heteryl)-2-(4-hydroxy-5,6,7,8-tetrdhydrobenzo-[4,5]thieno[2,3-b]pyridin-3-yl)-3,4,5,6,7,8-hexahydrobenzo[4,5] thieno[2,3-d] pyrimid in-4-one 11–14 respectively.     

Synthesis of some sulfur-containing pyrido[1,2-α]pyrimidines

4-Methylthiopyrido[1,2-α]pyrimidin-2-one and 2-hydroxypyrido[1,2-α]pyrimidine-4-thione derivatives were synthesized by the addition ofN-(4-R-pyrid-2-yl)acetoacetamides (R = H, Me) to CS₂ under phase-transfer conditions followed by the alkylation of the reaction products with Mel. The molecular structure of 3-acetyl-4-methylthiopyrido[1,2-α]pyrimidin-2-one is established by X-ray analysis.     

An efficient synthesis of novel pyridothieno-fused thiazolo[3,2-a]pyrimidinones via Pictet–Spengler reaction

An efficient method for the synthesis of novel pyrido[3',2':4',5']thieno[3',2':2,3]pyrido [4,5:d][1,3]thiazolo[3,2-a]pyrimidine-4-one derivatives (5) has been developed using a Pictet-Spengler reaction between 2-(3-aminothieno[2,3-b]pyridin-2-yl)thiazolo[3,2-a] pyrimidin-5-one (3), which could be obtained from the condensation of 7-(chloromethyl)-5H-thiazolo[3,2-a]pyrimidin-5-one (1) with 3-cyanopyridine-2-thione (2) via Thorpe-Ziegler isomerization, and aromatic aldehydes under NH₂SO₃H as catalysis in good yields.