Thallation-iodination studies of heterocyclic systems

The thallation-iodination of 3-carbonylindoles ( 4a-f ) results in orientation control with substitution occurring at the 4-position ( 6a-f ). Also described is the dithallation of N-methylpyrrole-2-carboxaldehyde ( 2 ).     

Synthesis and properties of isoviagra. A 2‐methyl‐2H‐pyrazolo[4,3‐d]pyrirnidin‐7‐one isomer of viagra®

The synthesis and spectral properties (ir, ms, nmr) of a substituted 2‐methyl‐2H‐pyrazolo[4,3‐d]‐pyrimidin‐7‐one ( 3 ), an isomer of Viagra^®, are described. The key synthon, 4‐amino‐1‐methyl‐5‐propyl‐3‐pyrazolecarboxamide ( 7 ), is prepared via the reaction of ethyl 2,4‐dioxoheptanoate with methylhydrazine, followed by cyclization, nitration, amidation, and nitro group reduction. Interaction of 7 with 2‐ethoxyben‐zoyl chloride yielded the respective bis‐amide ( 8 ) which was cyclized in polyphosphoric acid to the corresponding pyrazolo[4,3‐d]pyrimidin‐7‐one derivative 9 . Chlorosulfonylation of 9 , and subsequent treatment with 1‐methylpiperazine furnished iso Viagra ( 3 ).     

Effect of some environmental ligands on the sorption of radionuclidesby peat humin

Summary In a previous paper we studied the interaction of the radionuclides ^110mAg, ⁶⁰Co and ⁶⁵Zn with peat humin. These nuclides are among the fission or corrosion products in nuclear reactors. The aim of this paper is to study the effect of certain ligands, which are present in the environment, such as humic acid, fulvic acid, EDTA and urea, on the sorption of these radionuclides by humin. The obtained results indicated that urea has no effect on the sorption of Co and Zn by humin, and only a little in case of Ag. However, the presence of the other ligands (humic acid, fulvic acid or EDTA) leads to different decreases in the sorption of the three nuclides by humin. The results are interpreted in the light of the complex formation between ligands and the metal cations and of the strength of binding of these cations to the humin sorbent. The release of Ag⁺in the presence of different ligands was found to follow the order: humic acid>EDTA>fulvic acid>urea. In the case of both Co²⁺and Zn²⁺, the sequence is changed to be: EDTA>humic acid>fulvic acid>urea, with a higher release in the case of Zn²⁺. The results showed that cobalt is bound more strongly to humin than silver and zinc. The sulphur content of the humic fractions plays a significant role in the competition for silver and zinc.     

Synthesis of heterocyclic and carbocyclic fluoro-olefins by ring-closing metathesis

[reaction: see text] Ring-closing metathesis (RCM) of vinyl fluoride-containing dienes in the presence of ruthenium alkylidene carbene complex 11 proceeded efficiently to give six- and seven-membered cyclic vinyl fluorides. The RCM reaction was used to prepare amine- and sulfamide-linked cyclo-olefins, as well as carbocyclic systems, from a simple commercial fluoro-olefin.     

Crystal structures of bis(4-dimethylaminopyridinium) tetrachlorocobaltate(II) and bis-[1,3-di (ammoniummethyl)benzene]tetrachlorocobaltate(II)

The crystal structures consist of organoammonium cations hydrogen bonded to tetrahedral CoCl₄ ^2– anions. In the 4-dimethylaminopyridinium salt, [(CH₃)₂NC₅H₅NH]₂CoCl₄, pairs of cations hydrogen bond in an asymmetric fashion to two of the chlorines in each anion. The planar cations form two sets of – stacks, first parallel to the a axis and the second parallel to the b axis. The anions lie between these two nonintersecting sets of stacks. In contrast, for the second compound, [C₆H₄(CH₂NH₃)₂]CoCl₄, the tetrahedral CoCl₄ ^2– anions form layers lying parallel to the bc plane. The 1,3-di(ammoniummethyl)benzene cations crosslink adjacent anionic layers, forming a lamellar structure of alternating organic and inorganic layers.     

Characteristics of GaSb growth using various gallium and antimony precursors

We report the epitaxial growth of GaSb using trimethylgallium (TMGa) or triethylgallium (TEGa) with trimethylantimony (TMSb), triethylantimony (TESb), or trisdimethylaminoantimony (TDMASb) in a low-pressure vertical rotating-disk reactor. Growth is kinetically limited for TMGa in the temperature range 560 to 640°C, and is mass-transport limited for TEGa in the range 525 to 640°C. A minimum V/III ratio is necessary to obtain stoichiometric GaSb, and is dependent on the pyrolysis temperature of Ga and Sb precursors. Featureless morphology is achieved for layers grown with TMGa or TEGa and TMSb, while surface defects are observed for layers grown with TEGa and TESb or TDMASb. These observations are consistent with Fourier transform infrared measurements, which indicate interactions between TEGa and TESb or TDMASb. All nominally undoped layers are p-type, with overall superior properties being obtained for layers grown with TEGa and TMSb. However, growth conditions that yield layers with the best electrical properties do not necessarily correspond to the same conditions for highest optical quality.     

Competitive hydrogen bonding and self‐assembly in poly(2‐vinyl pyridine)‐block‐poly(methyl methacrylate)/poly(hydroxyether of bisphenol A) blends

Blends of poly(2‐vinyl pyridine)‐block‐poly(methyl methacrylate) (P2VP‐b‐PMMA) and poly(hydroxyether of bisphenol A) (phenoxy) were prepared by solvent casting from chloroform solution. The specific interactions, phase behavior and nanostructure morphologies of these blends were investigated by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), dynamic light scattering (DLS), atomic force microscopy (AFM), and transmission electron microscopy (TEM). In this block copolymer/homopolymer blend system, it is established that competitive hydrogen bonding exists as both blocks of the P2VP‐b‐PMMA are capable of forming intermolecular hydrogen bonds with phenoxy. It was observed that the interaction between phenoxy and P2VP is stronger than that between phenoxy and PMMA. This imbalance in the intermolecular interactions and the repulsions between the two blocks of the diblock copolymer lead to a variety of phase morphologies. At low phenoxy concentration, spherical micelles are observed. As the concentration increases, PMMA begins to interact with phenoxy, leading to the changes of morphology from spherical to wormlike micelles and finally forms a homogenous system. A model is proposed to describe the self‐assembled nanostructures of the P2VP‐b‐PMMA/phenoxy blends, and the competitive hydrogen bonding is responsible for the morphological changes. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1894–1905, 2009     

Nonparametric density estimation for nonmixing approximable Stochastic Processes

The author deals with nonparametric density estimation for stochastic processes which satisfy the L _∞-approximability property. He considers a Parzen–Rosenblatt estimator of the density for general stationary L _∞-approximable processes. He states conditions under which it is consistent and investigates its rate of convergence. Finally, he applies his results to general nonmixing linear processes and nonmixing nonlinear autoregressive processes.     

On formation of singularities in one-dimensional nonlinear thermoelasticity

Dedicated to Bernard D. Coleman on the occasion of his 60^th birthday