Organic synthesis by means of noble metal complexes—XCIV : Palladium catalyzed hydrosilylation of monoenes and conjugated dienes

Palladium compounds and metallic palladium combined with phosphine are active catalysts of selective hydrosilylation of terminal olefins. Butadiene and trichlorosilane give a 1:1 adduct and trimethylsilane affords a 1:2 adduct. Special features of the palladium catalyzed hydrosilylation reactions are presented.     

Oxidative cleavage of 1-alkylcyclopentanols by lead tetraacetate-metal chloride system

Conclusions Oxoalkyl radicals are generated when the lead tetraacetate-alkali or alkaline earth metal chloride system is reacted with 1-alkylcyclopentanols, which are oxidized to chloroketones.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2383–2385, October, 1979.     

Oxygenative cleavage of catechols including protocatechuic acid with molecular oxygen in water catalysed by water-soluble non-heme iron(III) complexes in relevance to catechol dioxygenases

Catechol dioxygenase model oxygenations have been performed for the first time in water by using water-soluble nonheme iron(III) complexes, enabling the oxygenation of protocatechuic acid and other catechols.     

Organic synthesis by means of noble metal compound—LI : Palladium-catalyzed addition of butadiene to nitroalkanes

Butadiene reacts with nitroalkanes in the presence of triphenylphosphine complexes of palladium, α-Hydrogens of nitroalkanes are displaced with 2,7-octadienyl groups to give nitroolefins. The nitroolefins thus obtained are reduced to give novel long chain amines, which have a primary amino group at the middle of the carbon chain.     

Oxidative DNA cleavage by copper ternary complexes of 1,10-phenanthroline and ethylenediamine-sulfonamide derivatives

Ternary copper(II) complexes (1–3) of 1,10-phenanthroline and ethylenediamine-R-sulfonamide derivatives (R = benzene, toluene and naphthalene rings) have been synthesized and characterized with the aid of X-ray diffraction and spectroscopic and electrochemical techniques. The crystal structures of the complexes show that the coordination polyhedron around copper(II) is distorted square planar. Both 1,10-phenanthroline and ethylenediamine-R-sulfonamide act as bidentate ligands. The three structures are stabilized by π–π stacking interactions. The interaction of the complexes with calf thymus DNA has been investigated by thermal denaturation studies which indicated that DNA was stabilized in the presence of the compounds. The increase in DNA stability induced by the complexes follows the order: 3 > 2 > 1. All three complexes were found to be very efficient agents of plasmid DNA cleavage in the presence of ascorbate as reducing agent. Mechanistic studies of the DNA cleavage process performed with radical scavengers show that the reactive oxygen species involved in the DNA damage are the hydroxyl radical, singlet oxygen-like species, the superoxide* and hydrogen peroxide.     

Oxidative aromatization of 9,10-dihydroanthracenes using molecular oxygen promoted by activated carbon

Substituted 9,10-dihydroanthracenes were oxidatively aromatized to the corresponding anthracenes effectively by using molecular oxygen as an oxidant and activated carbon (Darco KB, Aldrich, Inc.) as a promoter in xylene.     

Stripping voltammetric determination of traces of catechol compounds preceded by adsorptive accumulation of metal complexes

Catechol compounds are quantified by controlled adsorptive accumulation of their metal complexes onto a hanging mercury drop electrode followed by stripping voltammetry. By using tin(IV) as a redox marker for quantifying the surface-bound species, selectivity can be improved relative to conventional oxidative methods; dopamine can be quantified in the presence of ascorbic acid. The method allows measurements of micromolar levels of catechol, dopamine, l-dopa, 3,4-dihydroxyphenylacetic acid and caffeic acid. The adsorptive stripping response is evaluated with respect to preconcentration time and potential, tin(IV) and analyte concentrations, stripping mode, reproducibility and possible interferences. Analogously, solochrome violet RS and dimethylglyoxime can be quantified after accumulation of their iron(III) and nickel(II) complexes, respectively. Detection limits are 7×10^?9 M for solochrome violet RS and 5×10^?8 M for caffeic acid (1- and 5-min preconcentration, respectively).     

Oxidative DNA cleavage by Cu(II) complexes of 1,10-phenanthroline-5,6-dione

A dimeric dichloro-bridged copper(II) complex [Cu₂(pdon)₂Cl₄] · 2DMF (1) and two mononuclear copper(II) complexes [Cu(pdon)(DMSO)Cl₂] · DMSO · H₂O (2) and [Cu(pdon)₃] · (ClO₄)₂ · 2.25CH₃CN · 6H₂O (3) (pdon = 1,10-phenanthroline-5,6-dione) have been synthesized and characterized. Variable-temperature magnetic susceptibility studies indicate the existence of weak anti-ferromagnetic coupling in the binuclear complex. The interaction of these complexes with CT-DNA (calf thymus DNA) has been studied using absorption and emission spectral methods. The apparent binding constants (K _app) for 1, 2 and 3 are 5.20 × 10⁵, 2.68 × 10⁵ and 7.05 × 10⁵ M^?1, respectively, showing moderate intercalative binding modes. All of these complexes cleave plasmid DNA to nicked DNA in a sequential manner as the concentration or reaction time is increased. The cleavage mechanism between the complex and plasmid DNA is likely to involve singlet oxygen ¹O₂ and ?OH as reactive oxygen species.     

聚四苯基卟啉及其金属配合物的XPS研究

用XPS 研守了聚四苯基卟啉及其18 种金属化合物, 证实了这些金属化合物为金属配合物. 由π→π* 激发能, 跃迁几率和N18 位移证明这些金属化合物是金属离子镶嵌在芳族大π体系共轭环中而成的金属配合物. 初步表明这些金属配合物的稳定性金属原子半径的增大而降低.     

Structural characterization of flavonoid glycosides by collisionally activated dissociation of metal complexes

Collisionally activated dissociation is used for structural characterization of a series of flavonoid glycosides. Dissociation of transition metal/flavonoid binary complexes of the type [MII(L - H+)]+ and transition metal/2,2'-bipyridine/flavonoid ternary complexes of the type [MII(L - H+)bpy]+ give fragmentation patterns that are complementary and more diagnostic than those of the protonated, deprotonated, or sodium-cationized flavonoids. Analysis of fragmentation patterns of the [MII(L - H+)bpy]- complexes permits determination of the disaccharide as a rutinose or neohesperidose and the relative placement of the disaccharide (i.e., 3 vs. 7 positions).     

Mechanism of oxygenative cleavage of catechols by nonheme iron complexes in relevance to catechol dioxygenases studied by quantum chemical calculations

Mechanism of oxygenative cleavage of catechols by nonheme iron complexes was studied by quantum chemical calculations. Calculations based on the density-functional theory indicate that all carbon atoms of the DMC and Cat ligands of [Fe^III(NH₃)₄(DMC)]⁺ (DMC: 3,5-dimethylcatecholate), [Fe^III(NH₃)₄(Cat)]⁺ and [Fe^II(NH₃)₄(Cat)] (Cat: catecholate) are positively charged, that is not favorable for the electrophilic attack. Significant amounts of the spin density, that are greater on oxygen than carbons, appear on the catecholate ligand. The spin density on aromatic carbon atoms is greater in the ferric complex than in the ferrous complex, supporting the Fe(II)-semiquinonate character of the ferric catecholate complexes. Results are obtained to support the probability of the initial binding of molecular oxygen to the iron center rather than to the aromatic carbons. In the step of the oxygen insertion into the C–C bond, formation of an epoxide-like structure is proposed. It is shown that the postulated intermediate can be converted to an oxygen-inserted product in the change of the electronic state from the anionic ligand to the neutral product.     

Stereoselectivity in reactions of metal complexes VII. Asymmetric synthesis of amino acids by metal ion-promoted transamination

Enantioselective synthesis of phenylalanine was performed by reacting phenylpyruvic acid with pyridoxamine followed by ketimine-aldimine isomerization of the Schiff base formed catalyzed by an optically active copper (II)-complex. By UV and CD measurements it was shown that the enantiomeric excess strongly depends on the reaction conditions and on the reaction time. In favorable cases it reached values up to 80%. The selectivity of the reaction is discussed on the basis of possible structures of the intermediate mixed ligand complex.     

Organic syntheses by means of metal complexes—XI : Copper complex catalyzed addition reactions of organic polyhalides to acrylic monomers

Telomerization, especially 1:2 adduct formation from organic polyhalides and acrylic monomers catalyzed by a copper complex has been studied. Reaction of carbon tetrachloride with acrylic monomers catalyzed by a copper salt gave a 1:2 adduct. Methyl trichloroacetate afforded a 1:2 adduct with acrylic monomers, addition of LiCl increased the yield. No 1:2 adduct was obtained from CHCl₃ even in the presence of LiCl. The 1:2 adduct formation mechanism is discussed.     

New synthesis of polyaromatics through oxidative polymerization by using metal complexes with air

The oxidative polymerization provides a new synthetic route to polyaromatics. Poly(p-phenylene sulfide) (PPS) is produced by oxidative polymerization of thiophenol with a vanadyl complex catalyst. The metal complexes act as an efficient catalyst of oxygen oxidative polymerization. The polymerization to yield PPS is discussed especially focusing on the catalytic mechanism of the complexes.     

New capabilities in extraction of platinum metal chloride complexes with oxygen-containing extractants

The efficiency of extraction of platinum metal chloride complexes with oxygen-containing extractants can be increased in going from acid chloride solutions to mixed acid sulfate-chloride solutions.