Journal of Synthetic Organic Chemistry, Japan
Online ISSN : 1883-6526
Print ISSN : 0037-9980
ISSN-L : 0037-9980
Current issue
Displaying 1-11 of 11 articles from this issue
Preface
Reviews and Accounts
  • Isao Mizota, Makoto Shimizu
    2024 Volume 82 Issue 7 Pages 670-683
    Published: July 01, 2024
    Released on J-STAGE: July 05, 2024
    JOURNAL RESTRICTED ACCESS

    Nucleophilic additions on imines occur mostly on imino carbons due to their polarization, whereas adducts on imino nitrogens are difficult. However, by adjusting the reaction conditions such as nucleophiles and reaction solvents, the selective N-addition reaction can proceed on the nitrogen atom. This reaction is known as an umpolung reaction, and is an attractive one that allows making nitrogen-carbon bonds at will. In this review, based on the umpolung reaction to α-imino esters, various types of umpolungs for their analogues and the development into biologically active compounds are provided. The review is divided into five parts, namely 1) α-imino allylesters, 2) α-imino thioesters, 3) N-silyl α-imino esters, 4) α-hydrazonoesters and 5) γ-hydrazono-β-ketoesters; here, the mechanism of the umpolung and their intermediates are discussed.

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  • Taku Shoji, Ryuta Sekiguchi, Shunji Ito
    2024 Volume 82 Issue 7 Pages 684-696
    Published: July 01, 2024
    Released on J-STAGE: July 05, 2024
    JOURNAL RESTRICTED ACCESS

    Azulene is a bicyclic aromatic compound consisting of a fused seven- and five-membered ring. In recent years, the synthesis of polycyclic aromatic compounds in which various aromatic compounds are fused to an azulene skeleton has been actively studied, and their unique optical properties have also been clarified. In this paper, we describe on the synthesis, reactivity, and optical properties of novel azulene-fused aromatic compounds that have been developed by the authors’ group.

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  • Takuya Suga, Yutaka Ukaji
    2024 Volume 82 Issue 7 Pages 697-708
    Published: July 01, 2024
    Released on J-STAGE: July 05, 2024
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    Alcohols, one of the most ubiquitous classes of organic compounds with myriad of feedstocks, have played essential roles as carbocation, carbanion and carbon radical equivalents in organic synthesis through appropriate functional group interconversions (FGIs). However, the relatively high thermal and chemical stiffness of hydroxy C-O bonds has prevented us from directly utilizing alcohols for such transformations. Our group envisioned that, by developing a method which allows us to skip cumbersome FGIs, we could bring about great “comfort” to the organic synthesis venue. This report overviews our recent efforts to directly generate carbon radicals from alcohols. Low-valent titanium (LVT) reagents were found to have an ability to homolytically cleave the C-O bond of hydroxy group. For example, LVTs derived from TiCl4(col) (col=2,4,6-collidine) and TiCl2(cat) (cat=catecholate) were reactive to benzylic and non-activated hydroxy groups, respectively. The generated carbon radicals were utilized to alkene insertion reactions and nickel-catalyzed cross-coupling reactions. Furthermore, the study was expanded to activation of non-strained ether C-O bonds. The catechol monoether directing group was newly developed for this purpose.

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  • Takashi Kurogi
    2024 Volume 82 Issue 7 Pages 709-718
    Published: July 01, 2024
    Released on J-STAGE: July 05, 2024
    JOURNAL RESTRICTED ACCESS

    Organometallic compounds have played a crucial role in organic synthesis, serving as carbanion equivalents that enable significant transformations and bond formations. While numerous protocols for generating monocarboanion species, such as Grignard reagents, have been well-established, the generation and utilization of geminal multi-carbanion species remain challenging and are still under development. In particular, examples of geminal tetracarbanion equivalents are rare, although geminal tetracarbanion species are anticipated to act as carbon-atom transfer reagents. Organometallic compounds bearing geminal tetracarbanion ligands are known as “carbide complex” in coordination chemistry. Here, we have focused on carbide complexes to exploit them for carbon-atom transfer reactions. This article describes the elucidation of chromium halocarbyne and carbide generated in the CX4/CrX2 reagent and their carbon-atom transfer reactivity.

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  • Hirokazu Kobayashi, Atsushi Fukuoka
    2024 Volume 82 Issue 7 Pages 719-730
    Published: July 01, 2024
    Released on J-STAGE: July 05, 2024
    JOURNAL RESTRICTED ACCESS

    Mechanical energies directly induce chemical reactions, which are called mechanochemical reactions. Different from the statistical behavior of thermochemical systems, mechanical forces accelerate chemical reactions by providing kinetic energies in particular directions or changing potential energy surfaces. Therefore, the mechanochemical reactions could provide characteristic results unique to the systems. In biorefinery, the selective conversion of cellulose and chitin, the top two most abundant biomass, is a grand challenge. However, we and other groups have clarified that mechanical forces enable the selective catalytic depolymerization of these polysaccharides. Specifically, liquid acid catalysts hydrolyze cellulose and chitin during ball-milling. Surprisingly, later, we found that activated carbons with weak acid sites more selectively hydrolyze chitin. This article summarizes the reaction behavior and mechanistic consideration of mechanochemical depolymerization of cellulose and chitin. Afterward, we briefly introduce the downstream processes for chitin utilization.

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Review de Debut
  • Ryota Sato
    2024 Volume 82 Issue 7 Pages 731-732
    Published: July 01, 2024
    Released on J-STAGE: July 05, 2024
    JOURNAL OPEN ACCESS

    Recent investigations have revealed that photoexcited nitroarenes, a class of abundant feedstocks, can be used as mild oxygen atom transfer (OAT) reagents under anaerobic conditions. One of the highly promising features of these reagents is their modifiable reactivity profile, which can be finely adjusted by altering the substitution pattern on the aromatic ring. This short review focuses on the application of photoexcited nitroarenes in radical [3+2] cycloaddition reactions and as reagents for hydrogen atom transfer (HAT).

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