Anti-HIV Active Naphthyl Analogues of HEPT and DABO

 5-Isopropyl-6-naphthyl uracil and 5-isopropyl-6-naphthyl-2-thiouracil were alkylated to give N-1-(ethoxymethyl and methylthiomethyl) uracil and S²-cyclohexyl-thiouracil, respectively. 5-Ethyl-6-naphthyl uracil and 5-ethyl-6-naphthyl-2-thiouracil afforded N-1-(ethoxymethyl, methoxy-methyl, methylthiomethyl, acetoxyethoxy methyl and hydroxyethoxy methyl) uracil and S²-((2,2- diethoxyethyl), methoxycarbonylmethyl, ethoxycarbonylpropyl, methylthiomethyl, ethoxymethyl, methyl and cyclohexyl)-thiouracil upon alkylation.     

Reactions of N , N -Disubstituted 5-Arylmethylidene-2-amino-thiazol-4(5 H )-ones with CH Acids

 N,N-Disubstituted 5-arylmethylidene-2-aminothiazol-4(5H)-ones reacted with diethyl malonate, ethyl benzoylacetate, acetylacetone, or cyclopentadiene in refluxing toluene and in presence of powdered sodium to give the respective 5-arylmethylidene-2′-amino-2,5′-bithiazolylidene-4,4′-dione derivatives in moderate yields. 5-Benzylidene-2-morpholin-4-yl-2-thiazol-4(5H)-one reacted with malononitrile in toluene and in presence of powdered sodium under mild conditions to afford the 1:1 adduct, benzylmalononitrile, and 2-morpholin-4-yl-2-thiazol-4(5H)-one. However, similar treatment of 5-(4-methoxyphenylmethylidene)-2-morpholin-4-yl-2-thiazol-4(5H)-one with malononitrile yielded the 2,5′-bithiazolylidene-4,4′-dione derivative together with 4-methoxyphenylmethylidene malononitrile. Treatment of 5-benzylidene- and 5-(4-methoxyphenylmethylidene)-2-morpholin-4-yl-2-thiazol-4(5H)-ones with 3-phenyl-4-oxo-2-thioxo-1,3-thiazolidine in refluxing toluene and in presence of powdered sodium produced 5-arylmethylidene-3-phenyl-4-oxo-2-thioxo-1,3-thiazolidines in good yields. The structures of all products were deduced from microanalytical and spectroscopic data, mechanistic details are discussed.     

Chemical and Optical Propertiesof New Highly Luminescent Alternating Oligo- m , p -phenylenevinylenes

 In this paper we report on the synthesis and characterization of a variety of poly-phenylenevinylene (PPV) derivatives containing para- and meta-linkages in the backbones. By the m-linkages the conjugation lengths of the oligo-m,p-phenylenevinylenes were limited, thus blueshifting the UV/Vis absorption and also the photoluminescence (PL) spectra. Alkoxy substituted oligo-m,p-phenylenevinylenes exhibited absorption and emission spectra at higher wavelengths than oligomers without oxygen directly attached to the backbone. Replacing p-phenylene by 4,4′-biphenylene moieties also led to a hypsochromic shift in the optical spectra. We chose the Heck coupling reaction to synthesize substituted oligomers consisting of alternating p-phenylenevinylene and m-phenylenevinylene units. They were characterized by ¹H NMR, ¹³C NMR, FT IR, UV/VIS, and GPC analysis.     

Synthesis of a New Series of Imidazo[1,5- d ]pyrido[2,3- b ][1,4]thiazines as Potential Ligands for the GABA Receptor Complex

 Starting from 2-chloro-3-nitropyridine, 1H-pyrido[2,3-b][1,4]thiazin-2(3H)-one was synthesized. This compound was reacted with potassium tert-butoxide and diethyl chlorophosphate to give the intermediate 1H-pyrido[2,3-b][1,4]thiazin-2-ylphosphate derivative, which in turn afforded the 1,2,4-oxadiazolylimidazo[1,5-d]pyrido[2,3-b]pyrazine derivatives. The title compounds are potential ligands for the γ-aminobutyric acid A/benzodiazepine receptor complex.     

An ab initio Molecular Orbital Study of the Conformational Properties of all-( Z )-Cyclododeca-1,4,7,10-tetraene

 Ab initio HF/6-31G^* and MP2/6-31G^*//HF/6-31G^* methods were used to calculate the structure optimization and conformational interconversion pathways for all-(Z )-cyclododeca-1,4,7,10-tetraene. This compound adopts the symmetrical crown (C _4v) conformation. Ring inversion takes place via symmetrical intermediates, such as boat-chair (BC, C _s) and twist (C _2h) conformers and requires about 22.3 kJ · mol⁻¹. The calculated strain energies for BC and twist conformers are 5.9 and 13.5 kJ · mol⁻¹. The results of semiempirical AM1 calculations for structural parameters and relative energies of the important geometries of the title compound are in good agreement with the results of ab initio methods.     

Microwave Assisted Deprotection of N , N -Dimethylhydrazones in Water Using Palladium Chloride–Tin Chloride as Catalyst

 N,N-Dimethylhydrazones of ketones and aldehydes undergo facile cleavage to the corresponding carbonyl compounds upon exposure to microwaves in water containing a catalytic amount of PdCl₂–SnCl₂ in high yields.     

Convenient Synthesis of 6 H -[1,2,4,5]Tetrazino[3,2- b ]quinazolin-6-ones

 The reaction of 3-amino-2-thioxo-4(1H)-quinazolinone or its 2-methylthio derivative with hydrazonoyl halides in the presence of ethanol and triethylamine affords 6H-[1,2,4,5]tetrazino[3, 2-b]quinazolin-6-ones.     

Replacement of Methoxy by tert -Butyl on a Naphthalene Residue: An Unexpected Reaction During a Snieckus ortho -Lithiation

 When 1-methoxy-2-naphthalene carboxylic acid diethylamide was reacted with tert-butyl lithium in presence of TMEDA and 3,5-dimethoxybenzaldehyde was subsequently added to the reaction mixture, (P, S/M, R)- and (P, R/M, S)-1-tert-butyl-3-((3,5-dimethoxyphenyl)-hydroxymethyl)-naphthalene-2-carboxylic acid diethylamide were formed instead of the corresponding 1-methoxy derivative. The diastereomeric relationship of the products is due to a sterically severely hindered rotation around the amide-aryl bond.     

Synthesis and structural studies of (2 E ,3 E ,6 R ,9 E ,11 E )-6-isopropenyl-3,6,10-trimethyl-5,8-dioxa-4,9-diazadodeca-3,9-diene-2,11-dione dioxime, ligand and its Mono-, homo, and heterodinuclear copper(II)/nickel(II) complexes

This article describes the synthesis of a new (2E,3E,6R,9E,11E)-6-isopropenyl-3,6,10-trimethyl-5,8-dioxa-4,9-diazadodeca-3,9-diene-2,11-dione dioxime (H₂hmdm), and its mono-, homo, and heterodinuclear copper(II)/nickel(II) complexes. Elemental analyses, stoichiometric and spectroscopic data of the metal complexes indicated that the metal ions are coordinated to the oxime and imine nitrogen atoms (C=N). The Cu(H₂hmdm), molecule coordinates to the second copper(II) ion through the oximate oxygens to afford a binuclear structure doubly bridged by the oximate groups in the cis arrangement. In the dinuclear complexes, in which the first Cu^II ion was complexed with nitrogen atoms of the oxime and imine groups, the second Cu^II ion is ligated with the 1,10-phenanthroline nitrogen atoms. Ligand and its mononuclear copper(II), homo and heterodinuclear copper(II)–nickel(II) complexes of (H₂hmdm) were characterized by elemental analyses, magnetic moments, ¹H-n.m.r. and ¹³C-n.m.r., i.r., and mass spectral studies. The data support the proposed structure of H₂hmdm and its complexes.     

Comparative Quantum-Chemical Analysis of the Electronic Structures of the Valence Regions of Active Sites in Cytochromes f and c.

A comparative analysis of densities of states has been carried out for the valence regions of the hemes and clusters of cytochromes f and c using the ZINDO1 semiempirical quantum-chemical method. The molecular orbitals of these structures are formed from the p atomic orbitals of nitrogen and carbon of the porphyrin ring, making equal contributions. For systems with negative charges, more than half of all added electrons are distributed over the porphyrin parts of the molecules. The molecular orbital energies of the valence regions of the corresponding clusters and hemes are nearly the same. In iron porphyrin, as well as in heme f and cytochrome cluster f, the lowest unoccupied molecular orbital is doubly degenerate. In heme c and cytochrome cluster c, the degeneracy is lifted because of the asymmetry of the nearest aminoacid environment and substituents in the porphyrin ring.     

On the Reaction between Alkyl Isocyanides and Ethynyl Phenyl Ketone in the Presence of N , N ′-Dimethylbarbituric Acid

 The reactive 1:1 intermediate produced in the reaction between alkyl isocyanides and ethynyl phenyl ketone was trapped with N,N ′-dimethylbarbituric acid to produce alkyl 1,3-dimethyl-2,4-dioxo-7-phenyl-1,3,4,5-tetrahydro-2H-pyrano[2,3-d]pyrimidine-5-carboxamides in good yields.     

The Unusual Thermodynamic Stability Order of the First-series Transition Metal Complexes with N,N,N′-tri(2-pyridylmethyl)glycinamide and the Crystal Structure of the Nickel(II) Complex

A new pentadentate tripodal peptide ligand N,N,N′-tri(2-pyridylmethyl)glycinamide (L) has been synthesized. The crystal structure of its nickel(II) complex, [NiL(H₂O)] · 1.17ClO₄ · 0.17H₃O · 0.03H₂O (1), has been determined by X-ray diffraction. In the complex, the deprotonated ligand L acts in a pentadentate fashion and coordinates to the nickel(II) ion through five nitrogen atoms, while the sixth position is occupied by a water molecule. The units of the complex are connected as a 3D honeycomb network by intermolecular hydrogen bonds. The thermodynamic properties of the ligand L with the first-series transition metal ions Co(II), Ni(II), Cu(II) and Zn(II) have been investigated by potentiometric titration and the results show that the order of their stability constants does not conform to the Irving–Williams serial. The reason why the stability constants of the Cu(II) complex are unconventionally small is proposed.     

UV-Induced Electrical and Optical Changes in PVC Blends

 2-Chloro-polyaniline (2-Cl-PANI) in its non-conducting (emeraldine base, EB) form, prepared by a chemical route, was dissolved together with poly-(vinylchloride) (PVC) in THF for casting into thin (10–50 μm) films. Upon exposure to UV radiation, the electrical conductivity of these films increased by more than 4 orders of magnitude (from 10⁻⁶ to 10⁻²S/cm). This is attributed to the dehydrochlorination of PVC by exposure to energetic photons and subsequent doping of 2-Cl-PANI (i.e. conversion to emeraldine salt, ES) by in situ created HCl. The doped films could be returned to their undoped form by exposure to NH₃ vapours. The UV-induced doping/NH₃ undoping cycles could be repeated several times. Various spectroscopic techniques were employed to follow the changes in the films upon exposure to UV radiation. The same photo-dehydrochlorination process has also been utilized for optical and/or lithographic purposes by preparing PVC blends containing methyl violet, and acid-base indicator dye. The photo-dehydrochlorination can be effectively sensitized by incorporating hydroquinone into the PVC blends containing methyl violet.     

Synthesis and Complexation of a New vic -Dioxime Ligand

 A new vic-dioxime ligand, N,N′-bis-(8-salicylideneimino-1-naphthyl)-diaminoglyoxime, has been synthesized from anti-dichloroglyoxime and 1-amino-8-salicylideneiminonaphthalene which has been prepared via the condensation product of 1,8-diaminonaphthalene and salicylaldehyde. The vic-dioxime ligand forms trinuclear complexes with Cu(II), Ni(II), Co(II), and Pd(II). The uranyl complex of this ligand has a 2:1 metal-ligand ratio and a binuclear structure with μ-hydroxo bridges.     

Microwave Assisted Mannich Reaction of Terminal Alkynes on Alumina

 Terminal alkynes, secondary amines, and formaldehyde undergo a Mannich reaction at room temperature in the presence of CuCl on Al₂O₃ without any organic solvent as reaction medium. The reaction can be promoted by microwave irradiation and is complete within one minute.     

Interaction of Dimethyltin(IV) with DNA Constituents

 The interaction of dimethyltin(IV) (DMT) with some selected DNA constituents was investigated potentiometrically. The stepwise formation constants of the complexes were determined, and the concentration distribution of the various complex species was evaluated as a function of pH. The effect of dioxane on the protonation constants of the ligands and the formation constants of dimethyltin(IV) complexes are discussed. The thermodynamic parameters Δ H° and ΔS° were calculated from the temperature dependence of the equilibrium constants.     

A Convenient Synthesis of NovelDerivatives of Pyrido[2,3- d ][1,2,4]triazolo[4,3- a ]pyrimidine-5,6-dione

 Reaction of 6-Amino-2-thiouracil with hydrazonoyl halides yielded regioselectively 7-amino-1,3-disubstituted-1,2,4-triazolo[4,3-a]pyrimidine derivatives. Upon treatment with methyl (Z)-2-benzoylamino-3-dimethylaminopropenoate, the corresponding methyl (Z)-2-benzoylamino-3-([1,2, 4]triazolo[4,3-a]pyrimidin-7-yl)-amino propenoates were obtained which cyclized in the presence of sodium ethoxide to afford novel derivatives of pyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine-5,6-(1H,8H)-diones.