Boric Acid as Highly Efficient Catalyst for the Synthesis of Phenols from Arylboronic Acids

A simple, efficient, and environmentally benign boric acid catalyzed methodology for the ipso‐hydroxylation of arylboronic acid to phenol has been developed using aqueous hydrogen peroxide as an oxidizing agent and ethanol as the solvent. The versatility of this protocol is that the reactions were performed at room temperature in short reaction time under metal‐, ligand‐, and base‐free conditions.     

Specific ion effects on adsorption at the solid/electrolyte interface: a probe into the concentration limit

Adsorption of organic acid at the mineral oxide-electrolyte interface has been explored. The adsorption of 2,4-dihydroxybenzoic acid onto α-alumina illustrates that specific ion effects show up at very low salt concentration (<0.05 mM). These surprising Hofmeister effects occur at salt concentrations an order of magnitude lower than in a previous study ( J. Colloid Interface Sci. 2010, 344, 482 ). Salts enhance adsorption and specifically at ≤0.05 mM. With increasing concentration of ion, the adsorption density decreases. The results are accounted for by incorporating the ion size and dispersion forces in the theoretical modeling based on ab initio calculations of polarizabilities. The order appears to be governed by ion size, determining the maximum concentration that ions can attain near the surface due to close packing.     

Synthesis and characterization of a flame retardant hyperbranched polyether

<正>A brominated hyperbranched polyether has been synthesized from cyanuric chloride and sodium salt of tetrabromobisphenol-A by an A_2+B_3 approach.The synthesized polyether was characterized by ~1H-NMR,~(13)C-NMR,UV, FTIR spectroscopy and X-ray diffraction studies,measurements of solution viscosity,molecular weight and solubility and elemental and thermogravimetric analyses.The flame retardancy of the synthesized polyether and its blends with commercially available plasticized poly(vinyl chloride)(PVC) and low density polyethylene(LDPE) was investigated by measurements of limiting oxygen index(LOI) value and thermogravimetric analysis.The properties are compared with a non-halogenated similar type of bisphenol-A based aromatic polyether after blending at different dose levels with the same base polymers.The LOI values of these blends indicated that these hyperbranched polyethers acted as flame retardant additives,and antimony trioxide had prominent synergistic effect with the bromo hyperbranched polyether for the above base polymers,and an increment of 4 to 6 units in LOI values was observed.     

Studies on uracils: A facile one‐pot synthesis of pyrazolo[3,4‐d]pyrimidines

The reaction of 6‐hydrazino uracils 1 and nitrones 2 result in an efficient one‐pot synthesis of pyrazolo[3,4‐d]pyrimidines 3 in excellent yields. The isolation of the by‐product aniline from the reaction mixture supported the plausible mechanism for the formation of pyrazolo[3,4‐d]pyrimidines.     

Synthesis of 1,3-Dioxanes Catalyzed by TsOH-SiO2 Under Solvent-Free Conditions

Silica-supported p-toluene sulfonic acid is found to be an excellent catalyst for the Prins reaction to produce 1,3-dioxanes in good yields from olefins and aliphatic aldehydes in dichloromethane at room temperature and solventless microwave irradiation within a short reaction time.     

Development of hydrophobic polyurethane film from structurally modified castor oil and its anticorrosive performance

Hydrophobic polyurethane (PU) films are widely used for various commercial and industrial applications due to their excellent water repelling and self-cleaning property. Nevertheless, achieving appreciable hydrophobicity in PU film is quite a challenge. Herein, we report on the development of a novel hydrophobic PU (fluorinated polyurethane [FCO-PU]) film and comprehensively evaluate its anticorrosive property. The FCO-PU was prepared by structural modification of castor oil (CO) through attachment of long fluorocarbon chains as pendant groups onto the backbone of CO. A model PU film (CO-PU) was also prepared from unmodified CO to compare the properties of FCO-PU film. All intermediate compounds, FCO-PU and CO-PU films were characterized by various spectroscopic techniques. Morphological, thermal and mechanical properties of the PU films were analyzed by field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical thermal analysis (DMTA) studies. Successful introduction of long fluorocarbon chains into the FCO-PU film is reflected by its high hydrophobicity with a water contact angle of 119.1°, compared to the model CO-PU film with a water contact angle of 84.4°. Anticorrosive properties of the PU films were evaluated by polarization technique and electrochemical impedance spectroscopy under corrosive environment and the obtained results reveal a significant corrosion resistance (corrosion rate: 6.72 × 10⁻⁶ mm/year) behavior by the FCO-PU film. This work represents an effective strategy for the backbone modification of CO to develop novel functional PU materials.     

Palladium complexes of P,P and P,S type bidentate ligands: Implication in Suzuki–Miyaura cross-coupling reaction

New palladium complexes of the type [PdCl₂(η²–P∩P)] (1a,1b) and [PdCl₂(η²–P∩S)] (1c,1d) have been synthesised by the reaction of PdCl₂ with P,P and P,S type bidentate ligands in 1:1 mol ratio, where, P∩P = 9,9–dimethyl-4,5-bis(diphenylphosphanyl) xanthene {Xantphos}(a) or bis(2-diphenylphosphanylphenyl)ether{DPEphos}(b); P∩S = 9,9-dimethyl-4,5-bis(diphenyl -phosphanyl) xanthenemonosulfide {Xantphos(S)}(c) or bis(2-diphenylphosphanyl phenyl) ether monosulfide {DPEphos(S)}(d). The complexes are characterized by elemental analyses, mass spectrometry, ¹H, ¹³C and ³¹P NMR spectroscopy together with the single crystal X-ray structure determination of 1a and 1d. The palladium atom in all the complexes occupies the centre of a slightly distorted square planar environment formed by a P atom, a P/S atom and two Cl atoms. The catalytic activities of 1a–1d investigated for Suzuki–Miyaura cross-coupling reactions at room temperature exhibit higher yield of the coupling products than catalysed by PdCl₂ itself. Among 1a–1d, the palladium complexes of bidentate phosphine (1a, 1b) show higher efficacy than their monosulfide analogues (1c, 1d). However, the recycling experiments with the catalysts for a selected coupling reaction between 4-bromobenzonitrile and phenylboronic acid exhibit that 1c and 1d are more efficient than 1a and 1b, which may be due to the donor effect of the P,S ligands during catalytic reaction.     

Acetanilide palladacycle: an efficient catalyst for room‐temperature Suzuki–Miyaura cross‐coupling reaction

The catalytic activity of three acetanilide palladacycles derived from easily accessible and commercially available acetanilide derivatives, viz. N‐phenylacetamide ( L1 ), N‐(4‐chlorophenyl)acetamide ( L2 ) and N‐(4‐methylphenyl)acetamide ( L3 ) has been examined in Pd‐catalyzed Suzuki–Miyaura reaction of arylboronic acid with aryl bromides at room temperature. The complex 1L3 exhibited efficient activity in the Suzuki–Miyaura reaction (up to 99% isolated yield) under mild reaction conditions. Copyright © 2014 John Wiley & Sons, Ltd.