Facile synthesis route to highly crystalline mesoporous γ-MnO2 nanospheres

Hierarchical mesoporous γ-MnO₂ nanospheres with high crystallinity were prepared by a template-free self-assembly under applied ultrasonic waves, resulting in a solid spherical nanostructure with stacking of nanosized worm-like particles. This approach based on ultrasound exposure reduces the particle size and enhances the crystallinity of γ-MnO₂, leading to a large effective area for the active domains and a stable structural arrangement of the active materials. The applicability of γ-MnO₂ to high-power lithium batteries is demonstrated, based on improved capacity, excellent rate capability, and stable cyclability, which stem from the outstanding physical properties of the hierarchical mesoporous nanostructure.     

Tin(IV) triflimidate-catalyzed cyclization of epoxy esters to functionalized δ-hydroxy-γ-lactones

In the presence of 5 mol % of tin(IV) triflimidate, a cyclization reaction of epoxyesters to δ-hydroxy-γ-lactones proceeding in 46-98% yields without additives, ligands, or co-catalysts was observed. The cyclization to five-membered rings is greatly favored compared to the possible six-membered rings formation and is probably under the control of a Thorpe-Ingold type effect.     

Nitroalkylation and nitroalkenylation reactions of γ-lactone enolates. A facile ring switch from polysubstituted γ-lactones to polysubstituted γ-lactams

Michael addition of lithium enolates of γ-butyrolactone 1 and α-methyl-γ-butyrolactone 1′ to (E)-1-nitropropene 2, (E)-β-nitrostyrene 3 and (E)-2-nitro-1-phenylpropene 4 is described. Reactions of the lithium enolate of 1′ with 2 and 4 occurred with high diasteroselectivity (80 and 92% d.e., respectively). Reactions of the zinc enolate of 1′ with two β-nitroenamines and two methylthio-substituted 1-amino-2-nitro-1,3-dienes were also examined. Catalytic reduction of the nitroalkylated and nitroalkenylated products allowed the achievement of functionalized γ-lactams and/or cyclic hydroxamic acids.     

PhI(OAc)2/KI mediated 1,2-acetoxysulfenylation of alkenes: facile synthesis of β-acetoxysulfides

A convenient method for 1,2-acetoxysulfenylation of alkenes using disulfide promoted by (diacetoxyiodo)benzene (PhI(OAc)₂, DIB)/KI was developed. The reaction is highly regioselective for styrene derivatives while aliphatic alkenes lead to a mixture of two regioisomers.     

Desilylation of α-trimethylsilylmethylene-δ-lactones. A new route to α-methylene-δ-lactones

Addition of phenylthiol to α-trimethylsilylmethylene-δ-lactones affords α-phenylthi(trimethylsilyl)methyl-δ-lactones which, on treatment with tetrabutyl-ammonium fluoride and methyl acrylate give the corresponding α-methylene-δ-lactones through a one-pot double deblocking process.     

A facile route to growth of γ-MnOOH nanorods and electrochemical capacitance properties

Single crystal nanorods of γ-MnOOH with lengths up to hundreds of nanometers were successfully prepared employing a novel solvothermal process based on the redox reaction between potassium permanganate (KMnO(4)) and N, N-dimethyl ammonium formate (DMF) without extra surfactant or template. The as-prepared products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and Fourier transformed infrared spectroscopy (FTIR). The electrochemical properties of γ-MnOOH nanorods were investigated by cyclic voltammetry and galvanostatic charge-discharge performance measurements. Specific capacitance (C(s)) calculated from the galvanostatic discharge curve was 131.9 F g(-1) for γ-MnOOH nanorods at the current density of 0.5 A g(-1). The electrochemical experiment results demonstrate that γ-MnOOH nanorods should be a good candidate as electrode material for supercapacitor.     

Catalytic enantioselective allylation of aldehydes using β-amido functionalized allylstannanes with chiral In(OTf)3/i-Pr-pybox complexes

The enantioselective allylation of aldehydes using a variety of β-amido functionalized allyltributylstannanes proceeded smoothly with good to high yields and enantioselectivities in the presence of 10 mol % of a chiral catalytic complex prepared from In(OTf)₃ and 2,6-bis[(S)-4-isopropyloxazolin-2-yl]pyridine {(S)-i-Pr-pybox}, providing the corresponding chiral γ-hydroxy amides.     

Enzyme mediated kinetic resolution of δ-hydroxy-α,β-unsaturated esters as a route to optically active δ-lactones

A novel synthetic route to optically active saturated and unsaturated δ-lactones based on enzymatic kinetic resolution and ring-closing metathesis reactions has been proposed. The influence of temperature, co-solvent, organic additives and the substrate structure on the catalytic behavior of selected hydrolases was studied. The substantial impact of the organic co-solvent and surfactant type on the enzymatic activity and enantioselectivity was observed providing enantiomerically pure δ-hydroxy-α,β-unsaturated esters. The established protocol combining enzymatic kinetic resolution with ring closing metathesis was successfully applied in the synthesis of the enantiomerically pure (6R)-phenyl-5,6-dihydro-2H-pyran-2-one which plays crucial role in the synthesis of the number of bioactive compounds.     

Cu(OTf)2/Cu-catalyzed four-component reaction: a facile synthesis of α-alkoxytriazoles via click chemistry

Aldehyde, alcohol, azide, and alkyne undergo smooth coupling by means of acetal formation, azidation, and a subsequent ‘click reaction’ in the presence of copper(II) triflate and copper metal in acetonitrile to furnish α-alkoxy-1,2,3-triazoles in good yields. The method provides a convenient route to prepare a wide range of triazoles in a one-pot operation via a four-component reaction.     

A highly α-regioselective In(OTf)3-catalyzed N-nucleophilic substitution of cyclic Baylis-Hillman adducts with aromatic amines

The highly α-regioselective N-nucleophilic substitution of B-H adducts bearing five (1a-f) or six-membered ring (5a-e) moieties with aromatic amines (2a-e) was developed under the catalysis of In(OTf)₃ (10 mol%). During the reaction the allylic rearrangement from γ-product to α-product occurred, resulting in thermodynamically stable α-product predominately.     

Synthesis and crystal structure of new one-dimensional copper(II) complex [Cu4(En)2(μ1,1-N3)4(μ1,1,1-N3)2(μ1,3-N3)2]n

A new polymer azido-bridged copper(II) complex [Cu₄(En)₂(μ_1,1-N₃)₄(μ_1,1,1-N₃)₂(μ_1,3-N₃)₂] _n (I) (En = ethylenediamine) has been synthesized and crystallography characterized. Complex I shows one-dimensional coordination polymeric structure based on a tetranuclear cluster unit [Cu₄(En)₂(μ_1,1-N₃)₄(μ_1,1,1-N₃)₂(μ_1,3-N₃)₂], in which the azido ions display three different bridging modes.     

Synthesis,structure characterization and thermal properties of [Zr6(μ3-O)4(μ3-OH)4(OOCCH2Bu)9(μ2-OH)3]2

Oxo/hydoxo zirconium(IV) complex of the general formula [Zr₆(μ₃-O)₄(μ₃-OH)₄(OOCCH₂^tBu)₉(μ₂-OH)₃]₂ has been isolated, when Zr(OⁱPr)₄ reacted with a 2-fold excess of 3,3-dimethylbutyric acid. Single crystal X-ray diffraction data, collected at 103 and 153 K, showed that the studied compound crystallizes in hexagonal system (P6₃/m (no. 176)). Structure consists of dimers composed of [Zr₆(μ₃-O)₄(μ₃-OH)₄(OOCCH₂^tBu)₉] sub-units, linked by six μ₂-OH bridges. Infrared spectroscopic studies proved the presence of hydroxo groups in the structure of studied clusters and formation of different types of oxo/hydroxo bridges. The application of variable temperature infrared spectroscopy and differential scanning calorimetry revealed that the structure of this complex undergoes the phase transitions at 143–183 and 203–293 K. Comparison of spectral and crystallographic data suggests that these phase transitions might be related to changes in the strength of Zr–O bonds of μ₂-OH bridges linking complex sub-units, and change in symmetry of the crystal lattice (from hexagonal to trigonal). Analysis of thermogravimetric data showed that decomposition of [Zr₆(μ₃-O)₄(μ₃-OH)₄(OOCCH₂^tBu)₉(μ₂-OH)₃]₂ proceeds with complete conversion to ZrO₂ (monoclinic form) between 603 and 803 K.     

铋(Ⅲ)配合物Bi(1,10-phen)[S2CN(CH3)2]2(NO3),

Three bismuth（Ⅲ） complexes Bi（1,10-phen）[S2CN（CH3）2]2（NO3） （1）, {Bi（S2COCH3）[S2CNC6Hs（CH3）]2}2 （2） and [Bi（S2CNBu2）2（CH3OH）（NO3）]∞ （3） were synthesized and characterized by elemental analysis and IR spectra. Their crystal structures were determined by X-ray single crystal diffraction analysis. Studies show that complex 1 has a monomeric structure with the central bismuth atom eight-coordinated in a capped distorted pentagonal bipyramidal geometry. The complex 2 takes centrosymmetric dimeric structure and the bismuth atoms are seven-coordinated in distorted pentagonal bipyramidal geometry.In complex 3, the bismuth atoms are seven-coordinated in distorted pentagonal bipyramidal geometry by bridging nitrate O atoms and the resulting structure is onedimensional infinite chain polymer.     

In(OTf)3-mediated dehydrative annulation of β-ketothioamides with phenylglyoxal: one-pot access to diversely functionalized pyrrol-2-thiones

Indium triflate mediated first synthesis of diversely functionalized pyrrol-2-thiones has been developed by dehydrative annulation of β-ketothioamides with phenylglyoxal through the domino Knoevenagel condensation/cyclization cascade in one-pot. This new simple strategy not only utilizes readily accessible starting material, but also allows the construction of 5-membered azaheterocycle with one quaternary carbon center as a result of the formation of two new (C–C and C–N) bonds in a single operation.     

Synthesis and structural characterisation of the palladium N-heterocyclic carbene cluster complexes [Pd3(μ-CO)3(NHC)3] and [Pd3(μ-SO2)3(NHC)3]

The reduction of trans-[Pd(NHC)₂Cl₂] (NHC = IMes, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene; IⁱPr₂ = 1,3-bis-isopropylimidazol-2-ylidene) with potassium graphite under an atmosphere of CO affords the palladium NHC carbonyl clusters [Pd₃(μ-CO)₃(NHC)₃] (NHC = IMes, 1; IⁱPr₂, 3). Treatment of 1 with SO₂ at room temperature yields the bridging SO₂ complex [Pd₃(μ-SO₂)₃(IMes)₃] (4) in quantitative yield. Complexes 1, 3 and 4 have been structurally characterised by X-ray crystallography.     

Synthesis and crystal structure of [W3S4(Acac)3(PPh3)3]PF6 · 0.5CHCl3 and [W3S4(Hfac)3(PPh3)2Br] · 2CHCl3

New cluster complexes [W₃S₄(Acac)₃(PPh₃)₃]PF₆ · 0.5CHCl₃ (Acac = CH₃C(O)CHC(O)CH₃) (I) and [W₃S₄(Hfac)₃(PPh₃)₂Br] · 2CHCl₃ (Hfac = CF₃C(O)CHC(O)CF₃) (II) were synthesized. Their molecular and crystal structures were determined by X-ray diffraction. The cis-cis type of coordination of acetylacetonate and hexafluoroacetylacetonate ligands in I and II, respectively, was established, and the PPh₃ ligands were found in the trans-positions with respect to the “capping” sulfide ligand (μ³-S).     

Crystal structure of [Pd(NH3)4]3[Ir(NO2)6]2·H2O

A single crystal of [Pd(NH₃)₄]₃[Ir(NO₂)₆]₂·H₂O double complex salt is studied by X-ray diffraction. Crystallographic characteristics are as follows: a = 21.0335(5) ?, b = 8.0592(2) ?, c = 21.3452(5) ?, β = 91.254(1)°, V = 3617.43(15) ?³, P2₁/c space group, Z = 4, d _x = 2.714 g/cm³. Single-layer pseudohexagonal packing of complex anions is determined along the [−1 0 1] direction in the structure. Complex cations and crystallization water molecules are located between the mentioned layers.     

Novel chromium trinuclear trifluoroacetate complexes Cr3(μ3-O)(CF3COO)6(CH3COOH)2(CF3COO) and Cr3(μ3-O)(CF3COO)6(CH3COOH)2(THF): Synthesis and crystal structure

Novel anhydrous trinuclear ₃-oxo complexes of Cr(III), Cr₃(₃-O)(CF₃COO)₆(CH₃COOH)₂(CF₃COO) (I) and of Cr(III,III,II), Cr₃(₃-O)(CF₃COO)₆(CH₃COOH)₂(THF) (II) (where THF is (CH₂)₄O) are synthesized by anodic dissolution of metallic chromium in solutions of trifluoroacetic acid in acetonitrile and in tetrahydrofuran and their structures are studied by X-ray diffraction analysis. Complex I forms orthorhombic crystals with space group Pna2₁, a = 9.778(1) , b = 16.042(2) , c = 22.851(4) , Z = 4, R ₁ = 0.0332; complex II crystallizes in monoclinic system: space group P2₁/c, a = 9.866(1) , b = 17.895(2) , c = 21.167(4) , = 100.75(2)°, Z = 4, R = 0.0422. The average Cr-(₃-O) distances in compounds I and II are almost equal (1.943(3) and 1.927(3) ). An average length of the Cr-O bond in octahedral surrounding of metal atoms is different in complexes I and II (1.985(4) and 2.003(3) , respectively), which is specified by different oxidation states of the metal atom. The CrCr distances lie in an interval of 3.366(1)–3.337(1) .__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 4, 2005, pp. 266–272.Original Russian Text Copyright © 2005 by Glazunova, Boltalin, Troyanov.     

Oxidative cleavage of α-sulfonyl ketones to carboxylic acids with Ce(NH4)2(NO3)6

Tandem oxidative cleavage of α-sulfonyl arylketones 2 with the combination of Ce(NH₄)₂(NO₃)₆ and O₂ in MeCN afforded carboxylic acids 3 in moderate to good yields. The plausible reaction mechanism has been discussed.     

Facile and highly efficient light-induced PR3/CO ligand exchange: A novel approach to the synthesis of [(μ-SCH2NPrCH2S)Fe2(CO)4(PR3)2]

A straightforward and efficient transformation of the Fe-S complex [(μ-SCH₂NⁿPrCH₂S)Fe₂(CO)₆] to its double phosphine coordinated analogues [(μ-SCH₂NⁿPrCH₂S)Fe₂(CO)₄(PR₃)₂] (R = Ph, Me) is described. The single crystal structure of the PPh₃-disubstituted complex [(μ-SCH₂NⁿPrCH₂S)Fe₂(CO)₄(Ph₃P)₂] (3) showed that both of the phosphine ligands take an apical/apical instead of a basal/basal or an apical/basal configuration.