Catalyst-free Vicinal bromoazidation of olefins using TMSN3 and NBS

A rapid and efficient method has been developed for the synthesis of vicinal bromoazide directly from olefin using N-bromosuccinimide (NBS) and trimethylsilyl azide (TMSN₃) as the bromine and azide sources, respectively, without any catalyst in acetonitrile as solvent. The rate of reaction is remarkably fast in acetonitrile without catalyst to produce bromoazides in high yield.     

Chemical composition and antimicrobial activity of the inflorescence essential oil of Capillipedium parviflorum (R. Br.) Stapf. from India

Essential oil isolated from the inflorescences of Capillipedium parviflorum (R. Br.) Stapf., collected from Kumaon region of Western Himalaya, India, was investigated by GC and GC-MS. A total of 45 constituents representing 99.0% of the essential oil were identified. The major components of this oil were 4-undecanone (33.2%), 4-undecanol (29.7%), 4-nonanol (13.9%), α-muurolol (5.3%), 4-tridecanone (3.6%), methyl-2-oxo-nonanoate (3.1%), trans-2-hexenyl butanoate (1.1%) and 1-tetradecanol (1.0%). The antimicrobial activity of the essential oil was determined against eight Gram-positive and Gram-negative bacterial strains, as well as two fungal strains. The bioassay showed that the essential oil possessed good antibacterial activity.     

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.     

A note on Iwasawa µ-invariants of elliptic curves

Suppose that E ₁ and E ₂ are elliptic curves defined over ℚ and p is an odd prime where E ₁ and E ₂ have good ordinary reduction. In this paper, we generalize a theorem of Greenberg and Vatsal [3] and prove that if E ₁[p ⁱ ] and E ₂[p ⁱ ] are isomorphic as Galois modules for i = μ(E ₁), then μ(E ₁) ≤ μ(E ₂). If the isomorphism holds for i = μ(E ₁) + 1, then both the curves have same μ-invariants. We also discuss one numerical example.     

Zeta functions of orders in quadratic fields

The zeta function of a lattice over an order in a semisimpleQ-algebra introduced by L Solomon, is a generalization of Dedekind zeta function and has an Euler product in terms of local zeta functions. In this paper, the local zeta functions of localized orders in quadratic fields and hence the global ones are computed first by using Solomon's combinatorial method. Next the same formulae are obtained by considering orders in algebras (overp-adic fields) obtained by completing quadratic fields. In the complete case, the methods of integration initiated by Bushnell and Reiner to study Solomon's zeta functions are used.     

Physical, thermal, dielectric and chemical properties of a hyperbranched polyether and its linear analog

The hyperbranched and the linear polyethers were prepared by one-pot nucleophilic displacement polymerization technique using cyanuric chloride and aromatic diol as reported earlier. The physical, thermal, dielectric and chemical properties of the hyperbranched polyether and its linear analog have been studied. The amorphous character of both the polyethers was observed in XRD study. The solubility studies showed that the hyperbranched polyether has relatively higher solubility in different solvents compared to its linear analog. The thermal properties of both polymers have been studied by thermogravimetric (TG) and differential scanning calorimetric (DSC) analyses. The chemical resistance tests indicated that both polyethers are very good chemical resistances except in dilute aqueous alkali solution. The dielectric properties such as dielectric constant and loss factor for both polyethers have also been studied with respect to changes of frequency (50-500 kHz) and temperature (303-343 K).     

Oxidation of selected sugars with Mn(III)

Glucose, fructose, xylose, arabinose, and sucrose have been determined titrimetrically using manganese(III) sulfate as an oxidant. On reaction in the dark, glucose consumes 5, fructose 7, xylose and arabinose 6 each, and sucrose after hydrolysis 12 equivalents of Mn(III) per mole, respectively. Sucrose has also been estimated following other methods and the results have been compared. Two leaf sample extracts are analyzed for the determination of reducing sugar and total reducing matter and the results are compared with those obtained by the other method.     

Reaction parameters in the RAFT mediated dispersion polymerization of styrene

Monodisperse polystyrene (PS) particles were prepared by a living radical dispersion polymerization with a reversible addition‐fragmentation chain transfer (RAFT) agent in an ethanol medium. In the presence of RAFT agent, the effects of various reaction parameters on the characteristics of PS particles were systematically investigated. When no RAFT agent was involved, the number‐average molecular weight (M_n) of the PS particles increased from 17,800 to 30,000 g/mol, but the weight‐average diameter (D_w) decreased from 2.54 to 2.06 μm with the increase of poly(N‐vinylpyrrolidone) content from 4.0 to 16.0 wt %. No correlation between the M_n and the coefficient of variation (CV) was observed. However, when the RAFT concentration varied from 0 to 2.0 wt %, all of the conversion, M_n, D_w, CV, and polydispersity index (M_w/M_n) decreased. This indicates that the RAFT agent alters the inverse behavior between the molecular weight (MW) and particle size shown in the conventional dispersion polymerization. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 872–885, 2008     

An efficient synthesis of dihydro- and tetrahydropyrans via oxonium-ene cyclization reaction

An efficient method has been developed for the synthesis of 2,3-dihydropyrans and 4-methylenetetrahydropyrans from aldehydes and substituted homoallyl alcohols in benzene mediated by boron trifluoride etherate in good yields. The reaction proceeds via oxonium-ene reaction.