Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Volume 74 , Issue 8
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  • Munetaka OYAMA, Tomonari IMABAYASHI, Jinn-Hsuan HO, Tong-Ing HO
    2006 Volume 74 Issue 8 Pages 649-655
    Published: August 05, 2006
    Released: March 20, 2012
    JOURNALS FREE ACCESS
    The reactions of 3-substituted-diphenylamine cation radicals in acetonitrile were studied using an electron transfer stopped-flow method. In the reactions of the 3-chloro-diphenylamine cation radicals (mCl-DPA·+), the main reaction route was the formation of the benzidine dimer, which was similar to the case of the diphenylamine cation radical (DPA·+). Although the reaction of DPA·+ proceeded via the cation radical-cation radical coupling as verified from the rate law of −d[DPA·+]/dt=k[DPA·+]2, the present kinetic analysis has revealed that the decay rate of mCl-DPA·+ was dependent on the concentration of the neutral molecules, i.e., the rate law was expressed as −d[mCl-DPA·+]/dt=k[mCl-DPA·+]2 [mCl-DPA]. In contrast, the reaction of the 3-methoxy-diphenylamine cation radical (mMeO-DPA·+) was too fast to be observed using the stopped-flow method, which is quite in contrast to the 4-methoxy-diphenylamine cation radical (pMeO-DPA·+) which was very stable in acetonitrile. In the case of mMeO-DPA·+, the cyclization reaction was confirmed to proceed soon after the generation of mMeO-DPA·+, which is similar to the case of the 3-methyl-diphenylamine cation radical (mMe-DPA·+). Thus, it was found that the substituent on the 3-position changed the reaction pathways of DPA·+ significantly, as well as their reactivity.
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  • Hideo TANAKA, Shin-ya ARAI, Yoshinori ISHITOBI, Manabu KUROBOSHI, Sige ...
    2006 Volume 74 Issue 8 Pages 656-658
    Published: August 05, 2006
    Released: March 20, 2012
    JOURNALS FREE ACCESS
    Electrolysis of 2-azetidinone 3 in AcOH/CH3CN containing NaBr (2–10 equiv.) was carried out in an undivided cell fitted with two platinum electrodes to afford the corresponding N-bromo-2-azetidinones 2a, while a similar electrolysis in a divided cell afforded no appreciable amount of 2 but a small amount of 4-acetoxy-2-azetidinone 1 together with a complex mixture. Ring-expansion of 2-azetidinone 3 leading to 4 took place exclusively by electrolysis in methanol containing AcONa. On the other hand, N-iodination proceeded efficiently only in a divided cell in the presence of 2.5 equiv. of NaI. Reaction of N-bromo-2-azetidinone 2 with various nucleophiles, e.g., acetate, thiolate, and alkoxides, afforded no substitution products, resulting in the reductive debromination leading to 3, whereas with diphenyl disulfide, N-phenylsulfenyl-2-azetidinone 5 was mainly obtained.
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  • Manabu ISHIFUNE, Hajime YAMASHITA, Daisuke HASHIMOTO, Hiroshi KANESEI, ...
    2006 Volume 74 Issue 8 Pages 659-667
    Published: August 05, 2006
    Released: March 20, 2012
    JOURNALS FREE ACCESS
    The modified platinum electrodes having complexes of sodium with crown ether type ligands were prepared and utilized in the electroreduction of methyl decanoate (1) in the presence of t-BuOH as a proton donor and Bu4NClO4 as a supporting electrolyte. The product yield by using the modified platinum electrode having the complex of lithium or sodium ion with the monomeric ligand LA (MPt(A)–Na) was 46%. The use of the modified platinum electrodes having the complex of sodium ion with the polymeric ligands LB (MPt(B)–Na) or LC (MPt(C)–Na) gave the reduced product in 52% or 47% yield respectively. Durability of the electrodes, MPt(A)–Na and MPt(B)–Na, under the electroreduction conditions was not so high, however, the activity of the electrodes was found to be recovered by the re-complexation of sodium ion with the ligand on the surface of the used modified electrodes. The durability of the electrode MPt(C)–Na was satisfactory to use repeatedly, and the use of MPt(C)–Na as a cathode and NaClO4 instead of Bu4NClO4 as a supporting electrolyte gave the reduced product in 69% yield. Moreover, using the modified electrodes in the presence of anodically dissolved magnesium ion the reduced product was obtained in >90% yield.
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  • Kazuhiro YAMADA, Mitsutoshi OKANO
    2006 Volume 74 Issue 8 Pages 668-671
    Published: August 05, 2006
    Released: March 20, 2012
    JOURNALS FREE ACCESS
    Electrochemical synthesis of poly (cyclotetramethylenesilylene) was successfully carried out for the first time by reducing 1,1-dichlorosilacyclopentane in 1,2-dimethoxyethane using a platinum cathode and a silver anode. The resulting polymer had Mw=5–8×103 and a relatively broad absorption with its λmax at ca. 275 nm. The polymer was relatively stable to UV irradiation compared to a typical polysilane, poly (dibutylsilane). Copolymerization of 1,1-dichlorosilacyclopentane and dibutyldichlorosilane were also successful.
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  • Seiji SUGA, Mitsuru WATANABE, Chun-Hong SONG, Jun-ichi YOSHIDA
    2006 Volume 74 Issue 8 Pages 672-679
    Published: August 05, 2006
    Released: March 20, 2012
    JOURNALS FREE ACCESS
    A method for sequential introduction of two organic groups on the same or the different α-carbons of nitrogen has been developed based on a combination of the concept of electroauxiliary and the cation pool method. Selective introduction of two carbon nucleophiles into 2,5- or 2,2-position of pyrrolidine has been accomplished via sequential electrochemical oxidation of pyrrolidine derivatives containing two silyl groups as the electroauxiliaries. Introduction of two carbon nucleophiles into 2,6-position of piperidine was also successful. The products having two olefinic groups were effectively converted to nitrogen-containing spiro compounds using ring closing metathesis, and an application to formal synthesis of cephalotaxine was also carried out. These results clearly illustrate the synthetic utility and potential of the present approach, and open a new aspect of the synthesis of nitrogen-containing compounds.
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  • Ikuzo NISHIGUCHI, Kendrekar P. SUNDERRAO, Utako YAMAMOTO, Yoshimasa YA ...
    2006 Volume 74 Issue 8 Pages 680-684
    Published: August 05, 2006
    Released: March 20, 2012
    JOURNALS FREE ACCESS
    One-pot vicinal double C-carboalkoxylation of styrene derivatives has been developed by electroreduction in the presence of a large excess of N-carboalkoxyimidazoles in N,N-dimethylformamide (DMF) containing tetra-n-butylammonium bromide as a supporting electrolyte using an undivided cell equipped with Zn-plate as the anode and cathode under the constant current conditions until 6 F/mol of electricity passed through the system, to afford the corresponding phenylsuccinic acid esters in good to moderate yields. On the other hand, electroreduction of aromatic imine derivatives under the similar conditions brought about one-pot geminal double C-carboalkoxylation, giving the corresponding aryl aminomalonic esters in moderate yields. As one of the most plausible mechanism, electron transfer to carbon-carbon and carbon-nitrogen double bonds may involved as the first step, followed by electrophilic C-carboalkoxylation.
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Notes
  • Shin-ya KISHIOKA, Akifumi YAMADA
    2006 Volume 74 Issue 8 Pages 685-687
    Published: August 05, 2006
    Released: March 20, 2012
    JOURNALS FREE ACCESS
    Kinetics of mono and dimethoxy-substituted benzyl alcohols oxidation by electrogenerated phthalimido-N-oxyl radical were investigated using rotating disk electrode voltammetry. The kinetic data arranged in a Hammett correlation indicated the validity of the peculiar reactivity of veratryl alcohol.
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  • Kazunori ISHIZUKA, Shigehiro TAKAHASHI, Jun-ichi ANZAI
    2006 Volume 74 Issue 8 Pages 688-690
    Published: August 05, 2006
    Released: March 20, 2012
    JOURNALS FREE ACCESS
    The surface of a gold (Au) disk electrode was modified with a self-assembled monolayer consisting of phenylboronic acid residue to prepare a ribonucleoside-sensitive electrode. The cyclic voltammetric response of the modified electrode to [Fe(CN)6]3− ion dissolved in the sample solution was found to be dependent of the type of ribonucleoside and its concentration. In other words, the peak current in the cyclic voltammogram of [Fe(CN)6]3− ion was significantly decreased when uridine or cytidine was added in the working buffer, while the response to thymidine, 2′-deoxyuridine, and 2′-deoxycytidine was rather small. The voltammetric response was rationalized on the basis of the electrostatic repulsion between [Fe(CN)6]3− ion and the negatively-charged electrode surface, which originates from the addition of OH ion on the electrode as a result of the formation of phenylboronic acid-ribonucleoside conjugate on the surface of the monolayer.
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  • Ikuichiro IZUMI, Mikito YASUZAWA, Akira KUNUGI
    2006 Volume 74 Issue 8 Pages 691-693
    Published: August 05, 2006
    Released: March 20, 2012
    JOURNALS FREE ACCESS
    Indirect electroreductions of 4-methyl-4-trichloromethyl-p-quinone-(1)-arylimines using a sacrificial sulfur-graphite electrode (S-C electrode) caused the elimination of a trichloromethyl group to give the corresponding N-tolylarylamines, whose yields increased largely with an increase in temperature and by the addition of benzoic acid as a proton donor. Similarly, diimines with two trichloromethyl groups underwent the elimination of two trichloromethyl groups. The above indirect electroreduction using the S-C electrode was undertaken at the low cathodic overpotential, and gave high product yields compared with the direct electroreduction.
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