Study of liquid-phase dehydration of <Emphasis Type="Italic">d,l</Emphasis>-1-(4-aminophenyl)ethanol in the presence of acid catalysts

Thermal acid-catalyzed liquid-phase dehydration of 1-(4-aminophenyl)ethanol at 250–260°C and 30–100 mm Hg was studied. In the presence of KHSO₄ a 2:1 mixture of 1-amino-4-ethylbenzene with 4-aminostyrene is formed, the use of KHSO₄/KH₂PO₄ causes the formation of polymers, and the use of H₃BO₃ (≤ 0.26 wt %) in a mixture with KHSO₄ allows the preparation of pure 4-aminostyrene. The structure of the reaction products was confirmed by NMR spectroscopy and by authentic synthesis.     

A new and highly effective method for catalytic oxidation of alcohols to the corresponding carbonyl compounds using the tris[(2-oxazolinyl)phenolato]manganese(III)/Oxone®/n-Bu4NBr oxidation system

Oxone® (2KHSO₅·KHSO₄·K₂SO₄) in the presence of mer-tris[(2-oxazolinyl)phenolato]manganese(III), Mn(phox)₃, as catalyst under biphasic reaction conditions (CH₂Cl₂/H₂O) and tetra-n-butylammonium bromide as phase transfer agent efficiently oxidises alcohols to their corresponding aldehydes and ketones at room temperature with very short reaction times (5 min) and good to quantitative yields.     

A highly efficient and recyclable fluorous palladium catalyst for Heck reactions in water

Abstract  

A fluorous nano-palladium catalyst has been synthesized and characterized. The catalyst is highly active for the Heck reaction of aryl halides with substituted styrenes in water under air. The corresponding Heck products were obtained in high yields with good stereoselectivity (E/Z up to 98:2). In addition, the catalyst could be recovered by fluorous liquid–liquid separation and reused four times without significant loss of activity or stereoselectivity.     

Oxidative chlorination of 4-pentenols and other functionalized hydrocarbons

Substituted 4-pentenols undergo regio- and stereoselective chlorocyclization, when treated in solutions of dimethyl carbonate with chloride, a terminal oxidant, and a buffered proton source. Effective oxidants for liberating chlorine-like reactivity from chloride in the temperature range between 20 and 40 °C are tert-butyl hydroperoxide, activated by a titanium(IV) or a molybdenum(VI) ONO-chelate complex, and potassium monoperoxysulfate from the ternary salt 2KHSO₅·KHSO₄·K₂SO₄ (oxone^®). Substituents in the flexible part of the alkenol direct oxidative chlorocyclization 2,5-trans- and 2,4-cis-selectively. (E)-Configuration at the alkene translates anti-specifically into relative configuration of substituents at the β-chlorohydrin ether entity. A phenyl group bound to the terminal alkene carbon alters the inherent 5-exo-specificity for chlorocyclization of terminal 4-pentenols toward 6-endo-selectivity, as exemplified by synthesis of trans-3-chloro-2-phenyltetrahydropyran from (E)-5-phenyl-4-penten-1-ol in up to 74% yield. Competition kinetics show that 5-exo-chlorocyclization of 1-phenyl-4-penten-1-ol occurs at 40 °C 600 times faster than electrophilic aromatic chlorosubstitution of anisole. Prenyl-type alkenols undergo allylic chlorination with an ene-type selectivity, as exemplified in synthesis of a building block for the fragrance component rose oxide from citronellol.     

New data on the reaction of hexafluorothioacetone with styrenes

Hexafluorothioacetone, generated in situ from its cyclic dimer (1) in the presence of CsF catalyst was shown to react with styrene or 4-alkyl-styrenes (alkyl = c-hexyl, Me, t-Bu) forming the corresponding 2:1 Diels-Alder cycloadducts as major products. All cycloadducts were isolated, and the structure of two of them was established by single crystal X-ray diffraction. While 2-vinylnaphthalene, 4-CF₃- and 4-Cl-styrenes in the presence of CsF catalyst react with 1 producing the corresponding 1:1 Diels-Alder cycloadducts, 4-alkoxy styrenes were found to produce preferentially the corresponding thietanes. The reaction of styrenes with 1 was also found to be sensitive to the source of fluoride ion and the solvent.     

Investigation on the geometric and matrix effects and quantitative determination of K, Cl and S atomic fraction for biomass burning particles by Monte Carlo simulation

Using Monte Carlo simulation, the geometric and matrix effects on intensity and intensity ratio measured by EPMA were investigated for both synthetic particles and biomass burning particles. Three particulate standards, KCl, K₂SO₄, KHSO₄, were prepared and measured along with biomass burning particles. The modified CASINO program (University of Sherbrooke, Quebec, Canada) at the University of Antwerp, Belgium was used. The relative intensities obtained by the UA version of the CASINO program appear to be in line with those from experiments.The CASINO program and iterative procedures were applied to quantitatively determinate the atomic fraction of K, Cl and S in particulate standard and real samples. After correcting the geometric and matrix effects, the atomic fraction ratio of K to Cl in KCl sample was found to be 1.007±0.025, 0.996±0.013 and 1.011±0.019 for experiments with high voltages of 15, 20 and 25 keV, respectively. The same procedure was also applied to K₂SO₄ and KHSO₄ standard particle sample. The atomic fraction ratio of K to S was 1.945±0.049 (25 keV) for K₂SO₄ and 1.014±0.072 (20 keV) for KHSO₄. These ratios obtained are close to the theoretic values 1 or 2. Reasonable data were obtained for biomass burning particles, indicating that it is possible to perform chemical speciation.     

Electrical conduction studies in ferric-doped KHSO4 single crystals

Direct-current conductivity of ferric-doped (138, 267, and 490 ppm) single crystals of KHSO₄ has been studied. The mechanism for the dc conduction process is discussed. It is observed that the ferric ion forms a (Fe³⁺-two vacancies) complex and the enthaply for its formation is 0.09 ± 0.01 eV. It is proposed that each ferric ion removes two protons from each HSO₄ dimer. The conductivity plot shows the presence of intrinsic and extrinsic regions. It is proposed that in the intrinsic region the dimer of HSO^?₄ breaks reversibly to form a long-chain monomer-type structure. The conductivity in the KHSO₄ crystal is proposed to be controlled by the rotation of HSO^?₄ tetrahedra along the axis which contains no hydrogen atom. Isotherm calculation for the trivalent-doped system is applied to this crystal and the results are compared with Co²⁺-doped KHSO₄ crystal. The distribution coefficient of ferric ion in the KHSO₄ single crystal is calculated to be 4.5 × 10^?1. Ferric ion causes tapering in the crystal growth habit of KHSO₄ and it is believed to be due to the presence of (Fe³⁺-two vacancies) complex. The enthalpy values for the various other processes are as follows: enthalpy for the breakage of HSO^?₄ dimer (H_i) = 1.28 ± 0.01 eV; enthalpy for the rotation of HSO^?₄ tetrahedron (H_m) = 0.58 ± 0.01 eV.     

Two new silver(I) complexes with 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz): Preparation,characterization, crystal structure and alcohol oxidation activity in the presence of oxone

Two new silver(I) complexes ((tptz)Ag₂(NO₃)₂ and [Ag₅(tptz)₄](NO₃)₅) with 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) have been synthesized and characterized by X-ray diffraction, elemental analysis, ¹H NMR, IR, fluorescence, UV–Vis spectroscopy and electrochemistry. Oxidation of alcohols to their corresponding aldehydes and ketones was conducted with one of the Ag complexes as a catalyst, soluble enough in organic solvent, using oxone (2KHSO₅·KHSO₄·K₂SO₄) as an oxidant under biphasic reaction conditions (CH₂Cl₂/H₂O) and tetra-n-butylammonium bromide as phase transfer agent under air at room temperature.     

Microwave synthesis of bis(tetrazolato)-Pd complexes with PPh3 and water-soluble 1,3,5-triaza-7-phosphaadamantane (PTA). The first example of C-CN bond cleavage of propionitrile by a Pd Centre

[2 + 3] Cycloaddition reactions of the di(azido)-Pd^II complex trans-[Pd(N₃)₂(PPh₃)₂] (1) with an organonitrile RCN (2), under heating for 12 h, give the bis(tetrazolato) complexes trans-[Pd(N₄CR)₂(PPh₃)₂] (3) [R = Me (3a), Ph (3b), 4-ClC₆H₄ (3c), 4-FC₆H₄ (3d), 2-NC₅H₄ (3e), 3-NC₅H₄ (3f), 4-NC₅H₄ (3g)]. The reaction of trans-[Pd(N₃)₂(PPh₃)₂] (1) with propionitrile (2h) also affords, apart from trans-[Pd(N₄CEt)₂(PPh₃)₂] (3h), the unexpected mixed cyano-tetrazolato complex trans-[Pd(CN)(N₄CEt)(PPh₃)₂] (3h′) which is derived from the reaction of the bis(tetrazolato) 3h with propionitrile, with concomitant formation of 5-ethyl-1H-tetrazole, via a suggested unusual oxidative addition of the nitrile to Pd^II. The [2 + 3] cycloadditions of [Pd(N₃)₂(PTA)₂] (4) (PTA = 1,3,5-triaza-7-phosphaadamantane) with RCN (2), under heating for 12 h, give the bis(tetrazolato) complexes trans-[Pd(N₄CR)₂(PTA)₂] (5) [R = Ph (5a), 2-NC₅H₄ (5b), 3-NC₅H₄ (5c), 4-NC₅H₄ (5d)]. All these reactions are greatly accelerated by microwave irradiation (1 h, 125 °C, 300 W). Taking advantage of the hydro-solubility of PTA, a simple liberation of 5-phenyl-1H-tetrazole from the coordination sphere of trans-[Pd(N₄CPh)₂(PTA)₂] (5a) was achieved. The complexes were characterized by IR, ¹H, ¹³C{¹H} and ³¹P{¹H} NMR spectroscopies, ESI⁺-MS, elemental analyses and, for 3b, also by X-ray structure analysis. Weak agostic interactions between the CH groups of the triphenylphosphines and the palladium(II) centre were found.     

A Series of 1-D Lanthanide Coordination Polymers Based on [Ln4(μ3-OH)4] (Ln = Er, Tb, Gd) Cluster Units

Abstract  

A series of 1-D lanthanide coordination polymers [Ln(μ₃-OH)(pybz)(pa)] _n (Ln = Er (1), Tb (2), Gd (3), Hpybz = 4-pyridin-4-yl-benzoic acid, Hpa = 2-picolinic acid) based on [Ln₄(μ₃-OH)₄] cluster units have been hydrothermally synthesized and characterized by single crystal X-ray diffraction, IR, elemental analysis, and thermogravimetric analysis. X-ray crystal structure analyses reveal that 1–3 are isomorphous with tetragonal space group P [`4] \overline{4} 2₁c and comprise tetranuclear Ln–O clusters, in which four Ln³⁺ centers are joined together by four μ₃-bridging hydroxyl groups to form cubane-like [Ln₄(μ₃-OH)₄]⁸⁺ cores that are further linked by four μ₃-pa⁻ ligands to produce 1-D chains along the c-axis.     

Crystal Structures of Two Copper(I) Iodides: Chained [CuI(bta)] and Tetranuclear [(mdabco)<Subscript>2</Subscript>Cu<Subscript>4</Subscript>I<Subscript>6</Subscript>] (bta = Benzotriazole; mdabco = <Emphasis Type="Italic">N</Emphasis>-methyl-1,4-diazabicyclo[2,2,2]octane)

Abstract  

In methanol solutions, two types of organic N-donor ligands bta and dabco (bta = benzotriazole; dabco = 1,4-diazabicyclo[2,2,2]octane) were selected to react with CuI under the solvothermal conditions, creating two new copper(I) iodides as one-dimensional (1D) chained [CuI(bta)] 1 and tetranuclear [(mdabco)₂Cu₄I₆] (mdabco = N-methyl-1,4-diazabicyclo[2,2,2]octane). Note that mdabco derived from the solvothermal in situ alkylation reaction between dabco and methanol solvent. The photoluminescence analysis revealed that compound 2 is a potential fluorescence material with maximum emission at 506 nm.     

Copper-catalyzed borofunctionalization of styrenes with B2pin2 and CO

The construction of structurally complexed and high-value chemical molecules from simple and readily available feedstocks is a long-standing challenge to chemists. Here, we describe a copper-catalyzed borofunctionalization of styrenes with B₂pin₂ and carbon monoxide. A set of new sodium cyclic borates were obtained with NaO^tBu as the base. These unique sodium cyclic borates can be easily converted into a variety of multifunctional β-boryl vinyl esters, boryl carbonates, β-boryl aldehydes, and boryl vinyl ether. In addition, the procedure also features good functional group tolerance and utilizes CO as the C1 source.

A new copper-catalyzed borofunctionalization of styrenes with B₂pin₂ and carbon monoxide has been developed.     

Lanthanide-Organic Frameworks Based on {Ln<Subscript>4</Subscript>(μ<Subscript>3</Subscript>-OH)<Subscript>4</Subscript>(μ<Subscript>2</Subscript>-OH)<Subscript>2</Subscript>} Cluster Units

Abstract  

Three novel lanthanide-organic frameworks: [Ln₂(pyba)₃(μ₃-OH)₂(μ₂-OH)(H₂O)] _n (Ln = Er (1), Y (2), Dy (3) Hpyba = 4-pyridin-4-yl-benzoic acid) have been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. Structure analysis shows that each {Ln₄(μ₃-OH)₄(μ₂-OH)₂} cluster units interconnect to form 1-D chains, which are further linked by π–π interactions to make a 3-D supramolecular network structure. Furthermore, the IR, PXRD and TGA of compounds 1–3 were also studied.     

Spectrophotometric study of some Mn(II) ternary complexes and their analytical applications

Abstract  

New ternary complexes of Mn(II) with py, bipy, and terpy as primary ligand (L₁) and 2′,4′,5′,7′-tetraiodofluorescein (I₄FlCOOH) as secondary ligand (L₂) were prepared. The stoichiometry for these complexes was found to be Mn(II):L₁:L₂ = 1:2:1, and the complex formula proposed is [Mn(L₁)₂(I₄FlCOO)]⁺. The effect of substituent groups of L₂ and the nitrogen atoms of L₁ on complex formation with Mn(II) was studied. Moreover, the interference of some cations and anions in the determination of Mn(II) by this method was investigated and the interferences of Cu(II) and Fe(III) with Mn(II) in their corresponding alloys were considered. A simple, rapid, and sensitive spectrophotometric method for determination of Mn(II) in its salts and Mn in its alloys is suggested.     

Synthesis of polyhydroxylated ester analogs of the stilbene resveratrol using decarbonylative Heck couplings

Protected 3,5-hydroxy-benzoyl chlorides 3 were coupled with styrenes 4 to give hydroxylated stilbenes, analogs of resveratrol, an important antioxidant disease preventative agent isolated from grape skins and other dietary sources. Levulinate and chloroacetate protecting groups allowed for the selective production of mono- and di-acetate variations under palladium-N-heterocyclic carbene (NHC) catalyzed decarbonylative coupling conditions. Fluorinated analogs were also produced using Heck conditions with bromofluorobenzenes. Human HL-60 cell assays showed the 4′-acetoxy variant 11 to have improved activity (ED₅₀ 17 μM) relative to resveratrol (24 μM).     

Synthesis of gamma-hydroxy enones via persulfate oxidation of dienyl ethers.

The commercial oxidant “oxone” (2KHSO₄·K₂SO₄·KHSO₄) has been found to be a superior reagent for the gamma oxidation of dienyl ethers to axial gamma-hydroxy enones.     

Salt flux crystal growth of the titanyl arsenate NaTiO[AsO4]

Abstract  

The titanyl arsenate NaTiO[AsO₄] was synthesized in the form of colourless lath-shaped crystals from arsenic and titanium dioxide in a NaCl/KCl flux at 850 °C. NaTiO[AsO₄] crystallizes with the monoclinic low-temperature form LT-CaTiO[SiO₄], space group P2₁/c. The structure was refined from single crystal diffractometer data: a = 6.7170(9), b = 8.7707(12), c = 7.2447(10) ?, β = 114.77(1)°, wR2 = 0.0559, 789 F ² values, and 74 variables. NaTiO[AsO₄] is characterized by a topology common to a wide range of oxide structures of stoichiometry AMOXO₄. It consists of parallel chains of trans-corner-sharing TiO₆ octahedra, cross-linked by isolated AsO₄ tetrahedra.     

Solution structure of a seven coordinated manganese(II) complex via electrospray ionization mass spectrometry

The mononuclear complex [Mn(tptz)(CH₃COO)(OH₂)₂]NO₃ (1) was investigated by electrospray ionization mass spectrometry in aqueous solution at pH 4.5. Electrospray ionization mass spectrometry shows that mononuclear and dinuclear manganese cationic species are present in solution, probably in equilibrium with neutral 1. An experiment showed that the most important reaction in the presence of oxone (2KHSO₅·KHSO₄·K₂SO₄) is decoordination.     

Hydroxylammonium fluorometalate: synthesis and characterisation of a new fluorozincate

Abstract  

A new coordination compound of zinc fluoride and hydroxylammonium, (NH₃OH)₂ZnF₄, was obtained after dissolving zinc powder in hydrofluoric acid (40%) and adding solid hydroxylammonium fluoride. The colourless crystals were characterised chemically, magnetically, structurally by single-crystal X-ray diffraction analysis, and thermogravimetrically by TGA and DSC analysis. The structure consists of NH₃OH⁺ cations and ZnF₆ octahedra in which the metal ion lies on the inversion centre. Each of the ZnF₆ octahedra shares four of its vertices in a way that each vertex is shared between two octahedra. Oxygen and nitrogen atoms of hydroxylammonium cations are donors of hydrogen bonds. Hydroxylamonium fluorozincate crystallizes monoclinic, P21/c, with cell parameters a = 8.1604(4) ?, b = 5.8406(3) ?, c = 5.6586(2) ? and β = 94.745(3)°. The compound decomposes above 373 K in four steps, obtaining ZnO as the final residue. Magnetic properties of the compound were studied between 2 and 300 K, giving the prevailing diamagnetic behaviour with room temperature susceptibility of −9 × 10⁻⁵ emu mol⁻¹.     

Extraction and DFT study on the complexation of H3O+ ion with tetrakis(2-ethoxyethoxy)-tetra-p-tert-butylcalix[4]arene

Abstract  

Extraction experiments in the two-phase water/nitrobenzene system and γ-activity measurements were used to determine the stability constant of protonated tetrakis(2-ethoxyethoxy)-tetra-p-tert-butylcalix[4]arene in nitrobenzene saturated with water. Density functional theory (DFT) calculations were applied to derive the most probable structure of the tetrakis(2-ethoxyethoxy)-tetra-p-tert-butylcalix[4]arene·H₃O⁺ complex species.