1,3-Dipolar Addition of Methyl α-Diazoacetoacetate to Enamines： A New Synthetic Route to 5-Amino-4,5-dihydrofurans

The reaction of methyl α-diazoacetoacetate with enamines catalyzed by dirhodium and copper complexes underwent formal 1,3-dipolar addition to give 5-amino-4,5-dihydrofurans in moderate yields. The reaction was suggested to proceed via a nucleophilic addition of enamines to rnetal-carbenes and a subsequent intramolecular cyclization of the resulting zwitterionic intermediates.     

Synthesis of (meth)acrylate Block Copolymers by Ligated Anionic Polymerization

Synthetic potential of the ligated anionic polymerization (LAP) of acrylic and metacrylic esters initiated with methyl 2-lithioisobutyrate (MIB-Li) in the presence of an excess of alkali metal tert-alkoxides (prevailingly Li tert-butoxide) is presented. tert-Alkoxides form with ester-enolates, like MIB-Li, cross-aggregates of various composition, which tailor the environment of growing chain-ends, lower their nucleophilicity and restrict in this way the extent of side reactions, in particular self-termination of growing macroanions by back-biting reaction. Thus, stability of polymethacrylate living chains is sufficiently high for methacrylate and acrylate block copolymers to be synthesized. In the case of acrylate polymerization, reaction conditions must be optimized due to their high tendency to self-termination.     

Complexes of nitrilotrimethylphosphonic acid with cobalt, nickel, copper and zinc

Substances of the types MH₄ntmp, Mg₃[M(Hntmp)]₂, M₂H₂ntmp and Mg[M₂(Hntmp)]₂, where M = Co, Ni, Cu, Zn and H₆ntmp = N[CH₂PO(OH)₂]₃ were prepared. The sodium and cesium salts of the [Co(Hntmp)]³⁻ complexes were also prepared. The IR and electronic spectra and the experimental magnetic susceptibilities indicate that these are high-spin complexes. The coordination surroundings of the central atom consist of a highly distorted octahedron of the ligand oxygen atoms. The nitrogen atom is not coordinated to the central atom.     

钯催化的脱羧基烷基化反应

钯催化的脱羧基烷基化反应是构建碳碳键特别是手性碳的有效手段,其催化活性高,反应条件温和,对映选择性好.近年来该领域取得了长足的进步.介绍了5年来钯催化的脱羧基烷基化反应,主要是钯催化的对映选择性Tsuji反应及其在天然产物合成中的应用.     

Lithium adsorption on armchair graphene nanoribbons

Lithium adsorption on two dimensional graphene and armchair graphene nanoribbons is studied using advanced density functional theory calculations. The relative stability of different adsorption sites is investigated taking into account different ribbon widths, adsorbate densities, and spin states. We find the singlet spin state to be the true ground state of the systems considered. For this spin state, the binding energy increases with decreasing adatom density due to lower Coulomb repulsion between the partially charged Li atoms. At low adsorbate densities the favorable adsorption sites on the nanoribbons are found to be the hollow sites near the edges of the ribbon, whereas at higher densities, Li atoms tend to couple on next-nearest neighboring hexagons close to the ribbon's edge. Adsorption of the metal atoms is found to significantly decrease the bandgaps of all systems studied, turning them metallic for sufficiently large adatom densities. This suggests lithium doping as a possible route for bandgap engineering of graphitic systems.     

Cartan Subalgebras in C*-Algebras of Haus dorff étale Groupoids

The reduced C*-algebra of the interior of the isotropy in any Hausdorff étale groupoid G embeds as a C*-subalgebra M of the reduced C*-algebra of G. We prove that the set of pure states of M with unique extension is dense, and deduce that any representation of the reduced C*-algebra of G that is injective on M is faithful. We prove that there is a conditional expectation from the reduced C*-algebra of G onto M if and only if the interior of the isotropy in G is closed. Using this, we prove that when the interior of the isotropy is abelian and closed, M is a Cartan subalgebra. We prove that for a large class of groupoids G with abelian isotropy—including all Deaconu–Renault groupoids associated to discrete abelian groups—M is a maximal abelian subalgebra. In the specific case of k-graph groupoids, we deduce that M is always maximal abelian, but show by example that it is not always Cartan.     

New thermally stable and organosoluble heterocyclic poly(naphthaleneimide)s

As majority of polyheteroarylenes based on bis(naphthalic anhydrides), are difficult to process due to their infusiblity and insolubility in common organic solvents and solubility only in strong acids, this study is concerned with the synthesis and properties of new, easily processable polyimides and copolyimides containing naphthalene and oxadiazole rings. These polymers have been synthesized and their properties have been compared with regard to the influence of oxadiazole and naphthalene units on their physical properties. The polyimides were prepared by polycondensation reaction in solution of the aromatic diamines containing preformed oxadiazole ring with two dianhydrides having naphthalene units, at high temperature. Also, copolyimides were prepared by using a mixture of each naphthalene‐containing dianhydride, with hexafluoroisopropylidene‐dianhydride in the polycondensation reaction with the same diamino‐oxadiazoles. Most of the resulting polyimides and copolyimides were soluble in polar amidic solvents and in less polar solvents, and their solutions gave flexible films when spread onto glass plates. The thermal stability and glass transition temperature of these polyimides and copolyimides were measured and compared. The quality and the roughness of the spin‐coated films of these polymers were investigated by atomic force microscopy. The photoluminescence properties of the polymers in solution were studied to determine the color of emission. The UV absorption was also studied to determine the Stokes shift, and hence the possible reabsorption effects. The properties of the present polyimides make them attractive for applications in advanced optoelectronics and other related fields. Copyright © 2009 John Wiley & Sons, Ltd.     

Temperature-Dependent and pH-Responsive Pillar[5]arene-Based Complexes and Hydrogen-Bond-Based Supramolecular Pentagonal Boxes in Water

Supramolecular systems in water are of paramount importance and those based on hydrogen bonds are both intriguing and scarce. Here, after studying the peculiar host–guest complexes formed between per-dimethylamino-pillar[5]arene ( 1 ) and the bis-sulfonates 2 a – c , we describe the formation of the first hydrogen-bond-based supramolecular pentagonal boxes (SPBs), which are stable in water. These pH-responsive SPBs are constructed from 1 as a body, benzene polycarboxylic acids 3 a , b as lid compounds, and 2 a – c as guests. We demonstrate that encapsulation of 2 a – c in pillar[5]arene 1 and in the highly stable water-soluble SPBs, that is, 1(3 a) ₂ and 1(3 b) ₂, is both temperature and pH dependent and, quite interestingly, depends, on the nature of the lid compounds used for capping the boxes even at high pH. We also highlight the difference in the ¹H NMR characteristics of 2 b and 2 c in the cavity of 1 and the SPBs.