Nonstoichiometric polycondensation I. synthesis of polythioether from dibromomethane and 4,4′-thiobisbenzenethiol

High molecular weight poly(phenylene thioether) ( 3 ) was successfully obtained by the polycondensation of 4,4′-thiobisbenzenethiol ( 1 ) and dibromomethane ( 2 ) with a variety of feed ratios in the presence of 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) in 1-methyl-2-pyrrolidinone (NMP) at 75°C. The resulting polymer showed the maximum inherent viscosity (η_inh) of 0.50 dL/g in 4 h when 1.5 equivalents excess of 2 was used. The model reaction using benzenethiol ( 4 ) and dichloromethane ( 5 ) in the presence of DBU in deuterated dimethylsulfoxide (DMSO-d₆) at 25°C indicated that the rate of the second nucleophilic displacement reaction (k₂) is 61 times faster than that of the first one (k₁). The maximum of theoretical molecular weights calculated at various stoichiometric imbalance (S) under the condition of k₂/k₁ = 61 showed a good agreement with the experimental molecular weights at specific polymerization times.     

Cover Picture: Theoretical Study on the Halogen–Zinc Exchange Reaction by Using Organozincate Compounds (Chem. Eur. J. 23/2009)

Density functional theory and fragment‐energy analysis have been used to probe the mechanism of the halogen–zinc exchange reaction. In their Full Paper on page 5686 ff. , M. Uchiyama, S. Nakamura et al. discuss three important factors in this reaction: The effect of the halogen species, the effect of the alkyl ligand on zinc, and the effect of the substrate nature.

     

Improvement of Ni/SDC anode by alkaline earth metal oxide addition for direct methane–solid oxide fuel cells

The anodic performances of Ni/CeO₂–Sm₂O₃(Ni/SDC) modified by the addition of alkaline earth metal oxides (MgO, CaO, and SrO) were investigated for direct oxidation of CH₄ in solid oxide fuel cells (SOFCs). Although the initial power density of cell with Ni/SDC anode modified by the addition of CaO was slightly lower than that of cell with Ni/SDC, the former anode exhibited an excellent stability compared to the latter one. Such a high stability of Ni–CaO/SDC anode may come from the inhibition of carbon deposition in addition to the retained ionic conductivity of anode.     

Two significantly different conformations in crystal: formation of a molecular dimer governed by cation-π interactions

Two significantly different conformations were observed in crystal of 1, which form an unsymmetrical molecular dimer governed by cation-π interactions between a pyridinium cation and a phenyl ring, whereas compound 2 forms a head-to-tail type of dimer.     

Enantioselective synthesis of pyrrolidine-, piperidine-, and azepane-type N-heterocycles with α-alkenyl substitution: the CpRu-catalyzed dehydrative intramolecular N-allylation approach

A cationic CpRu complex of chiral picolinic acid derivatives [(R)- or (S)-Cl-Naph-PyCOOCH(2)CH═CH(2)] catalyzes asymmetric intramolecular dehydrative N-allylation of N-substituted ω-amino- and -aminocarbonyl allylic alcohols with a substrate/catalyst ratio of up to 2000 to give α-alkenyl pyrrolidine-, piperidine-, and azepane-type N-heterocycles with an enantiomer ratio of up to >99:1. The wide range of applicable N-substitutions, including Boc, Cbz, Ac, Bz, acryloyl, crotonoyl, formyl, and Ts, significantly facilitates further manipulation toward natural product synthesis.