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Volume 40, Issue 7
Displaying 1-9 of 9 articles from this issue
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Masakatsu SHIBASAKI, Shiro IKEGAMI1982 Volume 40 Issue 7 Pages 602-617
Published: July 01, 1982
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSThis article describes recent total synthesis of natural products, in which highly stereo-and regioselective reactions by internal chelation with metal salts are involved. The first part of the report presents a number of total syntheses of natural products, which use highly stereoselective carbon-carbon bond forming reactions by internal chelation with metal salts. In the second part, natural product synthesis, which involves highly stereoselective reductions by internal chelation, is discussed. The final two parts of the article present synthesis of natural products, in which chelation-controlled regioselective reactions are included.View full abstractDownload PDF (1683K) -
Tamotsu FUJISAWA, Toshio SATO1982 Volume 40 Issue 7 Pages 618-628
Published: July 01, 1982
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSRegioselective ring cleavage of small membered lactones provides the convenient synthesis of various types of carbon homologated carboxylic acids : e. g. highly strained four-membered lactones, such as β-propiolactones or diketene give three carbon homologated β-substituted propionic is acids or 3-methylenealkanoic acids, respectively, by the regioselective attack of organometallics to their β-carbons. On the other hand, lactones with an unsaturated group at their w position, such as β-vinyl- and β-ethynyl-β-propiolactones, γ-vinyl-γ-butyrolactone or δ-vinyl-δ-valerolactone give five, six, or seven carbon homologated carboxylic acids with olefinic bond (s), respectively, by SN2' reaction of the organocopper reagents with their terminal unsaturated carbons. These lactones are extremely useful as synthetic blocks for natural product syntheses due to the selective construction of carbon skeleton and an easy conversion of the carboxylic functional group to other functional ones. The synthetic utility of the lactones is demonstrated by the following natural products : perfumes and essential oils, insect pheromones and hormones, insecticides, and macrolides.View full abstractDownload PDF (1376K) -
Yoshikazu SUGIHARA, Takashi SUGIMURA1982 Volume 40 Issue 7 Pages 629-641
Published: July 01, 1982
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSStudies on valence isomers of cyclic conjugated systems, which are confined to valene-type and Dewar-type isomers of simple aromatic compounds, are reviewed. Synthesis and properties of tropovalene, azulvalene and Dewar azulene are described in detail.View full abstractDownload PDF (1716K) -
Keiji KOBAYASHI1982 Volume 40 Issue 7 Pages 642-650
Published: July 01, 1982
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSAlthough 1, 4-dithiin is comprised of a cyclic 8π-electron system, it is neither antiaromatic in character, nor aromatic as supposed earlier on the basis of possible dorbital participation. Its chemical properties are predominantly olefinic to provide versatile reactions with electrophiles as well as nucleophiles. In this article the advances of the chemistry of 1, 4-dithiins after early vintage by W. E. Parham are reviewed, covering the structure, preparation and reactivities.View full abstractDownload PDF (1134K) -
Ryoichi NAKAGAKI1982 Volume 40 Issue 7 Pages 651-657
Published: July 01, 1982
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSOrientation and mechanism in photoinduced aromatic substitutions were critically reviewed from the theoretical and experimental points of view. Four empirical rules proposed by Havinga et al. for photonucleophilic substitutions were re-examined and it was found that three of them can be rationalized by the frontier electron method. One of the empirical rules, merging resonance stabilization, was shown to lack sound theoretical basis, and it should therefore be replaced by an orientation rule for reactions involving one-electron transfer prior to σ-complex formation. The reaction mechanism of this type can be reasonably described by charge-transfer theory developed by Nagakura and Tanaka and referred as SN (ETANR) Ar* (Electron Transfer and Addition of the Nucleophile Radical). The mechanism of photocyanation of methoxy-substituted aromatics (e. g. substituted anisoles) was re-examined by referring to data on photoionization of the aromatic substrates. It may safely be concluded that the photocyanation of p-halogenoanisoles is not of the SRN+1 Ar* mechanism, but of the SN 2 Ar* type.View full abstractDownload PDF (905K) -
Yasumitsu TAMURA, Hiroyuki ISHIBASHI1982 Volume 40 Issue 7 Pages 658-666
Published: July 01, 1982
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSThe carbon-carbon bond forming reactions of 1-acyl-1-thiocarbocations are described. The cations can easily be generated from α-acyl-α-chlorosulfides under the Friedel-Crafts reaction conditions or from α-acylsulfoxides under the Pummerer reaction conditions. The reactions are classified into the following four features : 1) electrophilic aromatic substitution, 2) ene reaction, 3) olefin cyclization, and 4) cationic polar cycloaddition. Applications of these reactions to synthe-ses of some medicines and natural products are also mentioned.View full abstractDownload PDF (922K) -
Tsutomu NAKAMURA, Hideo MATSUZAWA1982 Volume 40 Issue 7 Pages 667-671
Published: July 01, 1982
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSDownload PDF (606K) -
Hiroshi FUJIHARA1982 Volume 40 Issue 7 Pages 672-673
Published: July 01, 1982
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSDownload PDF (192K) -
Masayuki MAEHARA1982 Volume 40 Issue 7 Pages 674-675
Published: July 01, 1982
Released on J-STAGE: November 13, 2009
JOURNAL FREE ACCESSDownload PDF (194K)
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