Microwave-assisted hydrothermal synthesis and electrochemical studies of α- and h-MoO<Subscript>3</Subscript>

Two modifications of molybdenum trioxide with orthorhombic (α-MoO₃) and hexagonal (h-MoO₃) crystal structure have been synthesized by a microwave-assisted hydrothermal method, facilitated by formic acid. Characterization by means of X-ray diffraction, scanning electron microscopy, specific surface analysis, and Fourier-transform infrared, Raman, and UV-Vis spectroscopy reveals phase-pure crystalline powder samples of hexagonal h-MoO₃ microrods and of α-MoO₃ nanobelt bundles, respectively. The electrochemical properties of the MoO₃ compounds, studied by cyclic voltammetry and galvanostatic cycling vs. Li/Li⁺, strongly depend on the structure and the applied potential range. In the range of 1.5–3.5 V, Li⁺-ions can be reversibly intercalated into the α-MoO₃ nanobelts. Utilizing the material in this way as intercalation cathode material yields an initial discharge capacity of 295 mA h g^?1 at 100 mA g^?1 and comparably moderate capacity fading of 25% between cycles 20 and 100. Extending the potential range to 0.01–3.0 V induces the conversion reaction to Mo, which for both modifications yields high initial capacities of around 1500 mA h g^?1 but is associated with much stronger capacity fading.     

Crystal Structures of α- and β-SrCeCuS<Subscript>3</Subscript>

The crystal structure of SrCeCuS₃, a complex sulfide synthesized for the first time, has been solved using X-ray powder diffraction data. The crystals are orthorhombic, space group Pnma. SrCeCuS₃ has two polymorphs: the high-temperature phase of Ba₂MnS₃ structural type (a = 8.1393(3) Å, b = 4.0587(2) Å, c = 15.9661(2) Å) and the low-temperature phase isostructural to BaLaCuS₃ (a = 11.1626(2) Å, b = 4.0970(2) Å, c = 11.5307(1) Å). The incongruent melting temperature and enthalpy of SrCeCuS₃ are, respectively, 1486 ± 3 K and 13.4 ± 1.5 J/g.     

Palladium-catalyzed cross-coupling of α-bromocarbonyls and allylic alcohols for the synthesis of α-aryl dicarbonyl compounds

The palladium-catalyzed coupling of olefins and organohalides is a versatile approach for synthesizing complex molecules from simple starting materials. We have developed a palladium-catalyzed coupling of α-bromocarbonyl compounds with allylic alcohols for the generation of acyclic aryl-substituted dicarbonyl compounds. The reaction proceeds via a tandem olefin insertion of an α-acyl radical followed by a 1,2-aryl migration. In addition to providing preliminary evidence for a free radical mediated mechanism, we demonstrate unprecedented levels of 1,3-stereoinduction for the 1,2-migration step.     

Viscous and dielectric properties of α-tocopherol and α-tocopherol acetate

This article presents the results of the shear viscosity and the dielectric relaxation measurements performed for α-tocopherol and α-tocopherol acetate, two principal compounds from the vitamin E group. The temperature dependence of the viscosity and dielectric relaxation time of the compounds can be very well reproduced with the Vogel–Fulcher–Tammann equation. It was found that for both tocopherols, the viscosity and the relaxation time attain their infinite high value (solid-like state) at the temperature of ～60 K below the transition to the glass state.     

Synthesis of new α-hydroxyphosphonates and α-acetoxyphosphonates

A series of new α-hydroxyphosphonate (5–14) have been synthesized in high yields by reaction of β-chloro-α,β-unsaturated aldehydes (1–4) and trialkyl phosphite in the presence of chlorotrimethylsilane at room temperature under solvent-free conditions. In addition, compounds (5–14) were reacted with acetic anhydride in DBU to give the new α-acetoxyphosphonate derivatives (15–23). All these phosphonates (5–23) were obtained as mixtures of two (E and Z) isomers and fully characterized by multinuclear (¹H, ¹³C, and ³¹P) NMR, IR spectroscopy and HRMS.     

Organocatalytic synthesis of α-hydroxy and α-aminophosphonates

A new and highly flexible procedure is described for the synthesis of α-amino- and α-hydroxy phosphonates. In the presence of a catalytic amount of oxalic acid (10 mol %), trimethyl phosphite reacts with aldehydes or imines (generated in situ from an aldehyde and an amine) to yield the corresponding coupled products in good yield.     

Synthesis and reactions of sulfur-substituted α,β-unsaturated δ- and γ-lactones

A new synthetic method for the preparation of sulfur-substituted α,β-unsaturated δ- and γ-lactones has been developed by reaction of the allylic bromides of 5,6-dihydro-2-pyridinones with NaOH in refluxing MeOH or t-BuOH. The substituents at C5 and C6 of these substrates are very important for the success of this reaction. Some synthetic transformations of the α,β-unsaturated δ-lactones have also been carried out.     

High performance liquid chromatographic separation of <Superscript>228,229</Superscript>Th and <Superscript>232,233</Superscript>U and their estimation by α- and γ-ray spectrometry

The activities of ^228,229Th and ^232,233U from an irradiated ThO₂ sample were radiochemicaly separated by using high performance liquid chromatography. Plancheted sources of the separated samples were made and the amount of ^232,233U and ^228,229Th were estimated by using alpha and gamma-ray spectrometric techniques. These estimations are important for the Th–U fuel reprocessing cycle of advanced heavy water reactor and accelerator driven sub-critical system.     

Accessing Cationic α-Silylated and α-Germylated Phosphorus Ylides

The synthesis and full characterization of α-silylated (α-SiCPs; 1 – 7 ) and α-germylated (α-GeCPs; 11 – 13 ) phosphorus ylides bearing one chloride substituent R₃PC(R¹)E(Cl)R²₂ (R=Ph; R¹=Me, Et, Ph; R²=Me, Et, iPr, Mes; E=Si, Ge) is presented. The molecular structures were determined by X-ray diffraction studies. The title compounds were applied in halide abstraction studies in order to access cationic species. The reaction of Ph₃PC(Me)Si(Cl)Me₂ ( 1 ) with Na[B(C₆F₅)₄] furnished the dimeric phosphonium-like dication [Ph₃PC(Me)SiMe₂]₂[B(C₆F₅)₄]₂ ( 8 ). The highly reactive, mesityl- or iPr-substituted cationic species [Ph₃PC(Me)SiMes₂][B(C₆F₅)₄] ( 9 ) and [Ph₃PC(Et)SiiPr₂][B(C₆F₅)₄] ( 10 ) could be characterized by NMR spectroscopy. Carrying out the halide abstraction reaction in the sterically demanding ether iPr₂O afforded the protonated α-SiCP [Ph₃PCH(Et)Si(Cl)iPr₂][B(C₆F₅)₄] ( 6 dec ) by sodium-mediated basic ether decomposition, whereas successfully synthesized [Ph₃PC(Et)SiiPr₂][B(C₆F₅)₄] ( 10 ) readily cleaves the F−C bond in fluorobenzene. Thus, the ambiphilic character of α-SiCPs is clearly demonstrated. The less reactive germanium analogue [Ph₃PC(Me)GeMes₂][B{3,5-(CF₃)₂C₆H₃}₄] ( 14 ) was obtained by treating 11 with Na[B{3,5-(CF₃)₂C₆H₃}₄] and fully characterized including by X-ray diffraction analysis. Structural parameters indicate a strong C_Ylide−Ge interaction with high double bond character, and consequently the C−E (E=Si, Ge) bonds in 9 , 10 and 14 were analyzed with NBO and AIM methods.     

Catalytic arylsulfonyl radical-triggered 1,5-enyne-bicyclizations and hydrosulfonylation of α,β-conjugates

A catalytic bicyclization reaction of 1,5-enynes anchored by α,β-conjugates with arylsulfonyl radicals generated in situ from sulfonyl hydrazides has been established using TBAI (20 mol%) and Cu(OAc)₂ (5 mol%) as co-catalysts under convenient conditions. In addition, the use of benzoyl peroxide (BPO) as the oxidant and pivalic acid (PivOH) as an additive was proven to be necessary for this reaction. The reactions occurred through 5-exo-dig/6-endo-trig bicyclizations and homolytic aromatic substitution (HAS) cascade mechanisms to give benzo[b]fluorens regioselectively. A similar catalytic process was developed for the synthesis of γ-ketosulfones. These reactions feature readily accessible starting materials and simple one-pot operation.     

Palladium-catalyzed Hiyama couplings of α-silylenoates and α-silylenamides

The Hiyama couplings of both α-silylenoates and α-silylenamides are described. These sensitive substrate classes require particularly specific conditions, employing both appropriate silicon-based species and a silver additive to realize high yields of the coupling products. Regioselective platinum-catalyzed hydrosilylations provide a direct and convenient entry into these stereodefined trisubstituted alkenes.     

Aliphatic α-nitroalkyl-<Emphasis Type="Italic">ONN</Emphasis>-azoxy compounds and their derivatives

Interaction of primary amines and 2,2-dimethyl-5-nitro-5-nitroso-1,3-dioxane in the presence of dibromoisocyanurate generates 2,2-dimethyl-5-nitro-1,3-dioxan-5-yl-ONN-azoxyalkanes. Based on the reaction of the latter with AcCl/MeOH followed by further transformations, the first representatives of mononitro- and polynitroalkyl-ONN-azoxyalkanes, i.e., (methyl-NNO-azoxy)nitromethane and dinitro(methyl-NNO-azoxy)methane, as well as some their derivatives, were prepared.     

Cyclothiomethylation of heterochain α,ω-diamines with formaldehyde and H<Subscript>2</Subscript>S

Cyclothiomethylation was performed of heterochain (O, S-S, NH) α,ω-diamines with formaldehyde and H₂S in aqueous medium at 20–60°C to obtain new α,ω-bis(1,3,5-dithiazinanes). The cyclocondensation of N-(3-aminopropyl)butane-1,4-diamine (spermidine), formaldehyde, and H₂S proceeds efficiently in the medium of BuOH-H₂O at 0°C and leads to the formation of previously unknown O,S-containing macroheterocycle, 1,7-dioxa-3,5,9,11-tetrathiacyclododecane. A fungicidal activity was found in 5,5′-(3,6-dioxaoctane-1,8-diyl)bis-1,3,5-dithiazinane with respect to microscopic fungi affecting agriculture.     

Reaction of nitroalkanes with levoglucosenone and its α-bromo and α-iodo derivatives. Cyclopentaannulation of α-halocyclenones

Michael reactions of levoglucosenone and its α-bromo and α-iodo derivatives with α,ω-dinitroalkanes were studied under conditions of chemical and electrochemical generation of base. Procedures were developed for stereospecific fusion of a cyclopentane ring to α-bromo- and α-iodolevoglucosenones, 2-iodocyclopent-2-en-1-one, and 2-iodocyclohex-2-en-1-one by the action of 2,2-dimethyl-1,3-dinitropropane.     

Scope and Limitations in the Use of α-Silyl and α-Stannyl Sulfones as Latent α-Sulfonyl Anions

Three methods for the regeneration of α-sulfonyl anions from α-silyl sulfones and α-stannyl sulfones are investigated. These methods include: (1) treatment of α-silyl sulfones with electrophiles (aldehydes and acid halides) in the presence of fluoride ion; (2) reaction of α-silyl sulfones with n-butyllithium which produces an α-silyl anion via a migration of the -SiMe₃ group from the α-position to the ortho-position of the phenyl sulfones; and (3) direct transmetalation of α-stannyl sulfone by treatment with n-butyllithium. The addition of cerium [III] chloride is shown to substantially decrease enolization problems associated with addition of α-sulfonyl anions to carbonyl compounds bearing enolizable protons.     

Click-chemistry approach to isoxazole-containing α-CF3-substituted α-aminocarboxylates and α-aminophosphonates

A convenient strategy for the synthesis of isoxazole-containing α-CF(3)-substituted α-aminocarboxylates and α-aminophosphonates have been developed. The method is based on copper-catalyzed 1,3-dipolar cycloaddition of different aromatic nitrile oxides to functionalized acetylenes.     

Synthesis,characterization and electrochemical properties of α-MoO<Subscript>3</Subscript> nanobelts for Li-ion batteries

Orthorhombic molybdenum trioxide (α-MoO₃) nanobelts have been successfully synthesized by hydrothermal method at 180°C for 20 h. The prepared α-MoO₃ samples were investigated by X-ray diffraction, Fourier transform IR spectroscopy, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy methods. It was found that α-MoO₃ nanobelts grow along the c-axis, with ±(100) top or bottom surfaces and ±(010) side surfaces. The prepared α-MoO₃ nanobelts were used as cathode materials for Li-ion batteries. They exhibit specific capacity of 1340 and 1250 mA h g^–1 at a current density of 100 and 400 mA/g, respectively.     

Purification and characterization of α-amylase from <Emphasis Type="Italic">Trichoderma pseudokoningii</Emphasis>

Background

Previous studies have demonstrated that members of Trichoderma are able to generate appreciable amount of extracellular amylase and glucoamylase on soluble potato starch. In this study the α-amylase was purified and characterized from Trichoderma pseudokoningii grown on orange peel under solid state fermentation (SSF).

Results

Five α-amylases A1-A5 from Trichodrma pseudokoningii were separated on DEAE-Sepharose column. The homogeneity of α-amylase A4 was detected after chromatography on Sephacryl S-200. α-Amylase A4 had molecular weight of 30 kDa by Sephacryl S-200 and SDS-PAGE. The enzyme had a broad pH optimum ranged from 4.5 to 8.5. The optimum temperature of A4 was 50 °C with high retention of its activity from 30 to 80 °C. The thermal stability of A4 was detected up to 50 °C and the enzyme was highly stable till 80 °C after 1 h incubation. All substrate analogues tested had amylase activity toward A4 ranged from 12 to 100% of its initial activity. The Km and Vmax values of A4 were 4 mg starch/ml and 0.74 μmol reducing sugar, respectively. The most of metals tested caused moderate inhibitory effect, except of Ca²⁺ and Mg²⁺ enhanced the activity. Hg²⁺ and Cd^+?2 strongly inhibited the activity of A4. EDTA as metal chelator caused strong inhibitory effect.

Conclusions

The properties of the purified α-amylase A4 from T. pseudokoningii meet the prerequisites needed for several applications.