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Volume 58, Issue 10
Displaying 1-8 of 8 articles from this issue
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Kazunori Hirabayashi, Atsunori Mori2000 Volume 58 Issue 10 Pages 926-933
Published: 2000
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSThis article reviews organic chemistry of siloxane and silanol involving the preparative method as well as applications towards organic synthesis. Chapter 1 deals with the formation of siloxane bond and reactions of thus prepared siloxane compounds. Chapter 2 covers recent preparative methods for silanols and new synthetic reaction using silanol involving 1) utilization of silanol oxygen that serves as a base or a nucleophile, 2) transformation of neighboring functionality on the silicon substituent based on the interaction of silanol oxygen with an organometallic reagent, and 3) transformation of a carbon silicon bond of silanols directed to novel carbon-carbon bond forming reactions.View full abstractDownload PDF (1213K) -
Akira Oku, Takashi Mori, Yuichi Sawada2000 Volume 58 Issue 10 Pages 934-944
Published: 2000
Released on J-STAGE: January 22, 2010
JOURNAL FREE ACCESSEthereal oxonium ylides are highly reactive and short-lived intermediates compared with other onium ylides. While they possess appreciable potential for synthetic use, e.g. in substituting one of the two ethereal ligands for a carbene-derived group, systematic use of this type of ylides for synthesis has been limited. Recently, we have found novel methods of controlling the reactivity of the ylides on the basis of designing intramolecular ketocarbenoid or carbene reactions with cyclic ethereal moieties. The findings are (1) use of protic nucleophiles for trapping the ylides in the form of oxonium ions to suppress both undesired side-reactions and dissociation to carbenes. Thus, with cyclic ethers, acetals and orthoesters, ring-enlargement reactions take place predominantly over sigmatropic pathways of oxonium ylides, thus enabling the synthesis of macrocycles bearing ketopolyether functionality. (2) Strained bicyclo [3.n.O] oxonium ylides derived from cyclic ethers undergo sigmatropic ring-cleavage reaction to give alkenyloxyketenes efficiently. (3) Silyl reagents can trap the ylides to form ring-enlarged enol silyl ethers, which are versatile intermediates for both the ring-enlargement and novel C-C bond formation reactions with carbon electrophiles. (4) Not only ketocarbenoids but also free alkylidenecarbenes bearing a cyclic ether or acetal group undergo the similar ring-enlargement. Similar reaction of sulfonium analogues is also described.View full abstractDownload PDF (1560K) -
Ligand Designs for the Remarkable Luminescence and Their EvolutionShozo Yanagida, Yasuchika Hasegawa, Mitsunori Iwamuro, Yuichiro Kawamu ...2000 Volume 58 Issue 10 Pages 945-955
Published: 2000
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSThe relatively low efficiency of Nd (III) emission in organic media has been improved by 1) suppression of the radiationless transition process via vibrational excitation of the surrounding medium, 2) prevention of dipole-dipole nonradiative energy transfer processes via energy migration, 3) suppression of radiationless transition of D2O molecules in the vicinity of Nd (III) complexes (formation of twelve-coordinate Nd (III) complex with DMSO-d6), 4) allowance of electron transitions of Nd (III) by the introduction of asymmetric ligand field, 5) photosensitization by use of energy transfer from organic ligands. The luminescence of NMI) was observed for the first time in undeuterated acetone when Nd (III) was complexed with bis-perfluorooctylsulfonylamine (pos). As to the applications of luminescent Nd (III) complexes, developments of luminescent lanthanide polymers and EL device were successful.View full abstractDownload PDF (2076K) -
Yoshitaka Araki, Toshiro Konoike2000 Volume 58 Issue 10 Pages 956-965
Published: 2000
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSRadical hydrostannylation of propargylic alcohols gives stannylated allylic alcohols regio- and stereoselectively, and subsequent β-elimination of stannyl alcohols (deoxystannylation) gives allenes in a one-pot process. Deoxystannylation proceeds in an anti-fashion by treatment with methanesulfonyl chloride and triethylamine at or below room temperature. Epoxidation or cyclopropanation of a chiral stannylated allylic alcohol and subsequent deoxystannylation affords a chiral allene oxide or alkylidenecyclopropane, respectively. A chiral allene oxide is isolated and characterized for the first time. [3] Cumulenes are synthesized from propargylic alcohols by the stannylation-deoxystannylation sequence. 1, 4-Elimination of stannylated propargylic alcohols as well as 1, 2-elimination of stannylated allenyl alcohols proceeds effectively to give [3] cumulenes. Deoxystannylation proves to be much more efficient than an analogous silyl counterpart because a vinylic carbon-tin bond is easily cleaved under mild reaction conditions.View full abstractDownload PDF (1600K) -
Shigenori Kashimura, Manabu Ishifune2000 Volume 58 Issue 10 Pages 966-974
Published: 2000
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSThe electroreduction of organochlorosilanes was carried out by using magnesium cathode and anode in a single compartment cell affording oligosilanes, polysilanes, and polycarbosilanes. The electroreductive coupling of organochlorosilanes gave the corresponding disilanes in high yield. The cross-coupling of chloroorganosilanes with dichloroorganosilanes under the same reaction conditions produced various types of oligosilanes such as trisilanes, tetrasilanes, and pentasilanes. This procedure was successfully applied to the stepwise elongation of silicon-silicon chains. The high efficiency of this electroreductive silicon-silicon bond formation reaction enabled the electroreductive synthesis of poly (alkylarylsilane) s having high molecular weight (Mn=5200-31000, Mw/Mn=1.4-1.8). The electroreductive polymerization of the dichlorosilanes bearing various types of functional groups was also carried out to afford the functionalized polysilanes. Moreover, the electroreductive polymerization of dichlorooligosilanes was successfully applied to the synthesis of sequence-ordered polysilanes. This electroreductive method was also applicable to the synthesis of poly-p- (disilanylene) phenylenes and silane-germane copolymers. The effects of electrode material, monomer concentration, amount of supplied electricity, and ultrasound were investigated in these reactions.View full abstractDownload PDF (1470K) -
Rational Drug Design in the Post-Genome EraHirokazu Iida, Hiroshi Sugiyama2000 Volume 58 Issue 10 Pages 975-987
Published: 2000
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSBy the completion of the human genome project, many diseases including cancer, hereditary and viral diseases can be understood by the DNA sequence level. Control of the specific gene expression will provide ultimate gene therapy. Minor groove binding polyamides containing N-methylpyrrole and N-methylimidazole amino acids exhibit promising performance based on the recognition of nucleic acid sequences. Various types of sequence-specific DNA binding agents are developed and used for the regulation of gene expression. We synthesized novel type of polyamide-alkylator conjugates. These synthetic compounds alkylated predetermined DNA sequences selectively, and also some of them possessed selective potency for certain cancer cell lines. In this review, we will focus on recent progress of minor groove binding polyamides that play important roles in the rational recognition of nucleic acid sequences. One of the future directions of rational design of molecular medicine in the post genome era is proposed.View full abstractDownload PDF (2044K) -
Kiyotaka Onitsuka, Shigetoshi Takahashi2000 Volume 58 Issue 10 Pages 988-999
Published: 2000
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSThis article describes recent advances in synthesis and catalysis of organometallic dendrimers involving transition metals. Some transition metal complexes have successfully been used as a building block for organometallic dendrimers classified as the main chain type. Some organometallic dendrimers of the surface and the core types have been applied to novel catalysts that can be easily recovered from the reaction mixture and are reusable for several times.View full abstractDownload PDF (1558K) -
[in Japanese], [in Japanese], [in Japanese], [in Japanese]2000 Volume 58 Issue 10 Pages 1000
Published: 2000
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSDownload PDF (207K)
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