• Title/Summary/Keyword: B. Chemical Synthesis

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Solid-phase Synthesis of 7-Aryl-benzo[b][1,4]oxazin-3(4H)-one Derivatives on a BOMBA Resin Utilizing the Smiles Rearrangement

  • Lee, Ji-Min;Yu, Eun-Ae;Park, Joo-Yeon;Ryu, In-Ae;Shin, Dong-Soo;Gong, Young-Dae
    • Bulletin of the Korean Chemical Society
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    • v.30 no.6
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    • pp.1325-1330
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    • 2009
  • A general method has been developed for the solid phase synthesis of drug-like 7-aryl-benzo[b][1,4]oxazin-3(4H)- one derivatives 6. The method relies on a novel, microwave irradiation promoted cyclization reaction of the BOMBA resin bound, N-substituted-$\alpha$-(2-chloro-4-bromophenoxy)acetamide 3 that takes place via a Smiles rearrangement. The 7-bromobenzo[1,4]oxazine 4, produced in this process is converted to 7-aryloxazin analogs 5 by utilizing Suzuki coupling with various substituted arylboronic acids. Finally, the target 7-aryl-benzo[b][1,4]oxazin-3(4H)-ones 6 are liberated from the resin by treatment with 5% TFA. The progress of the reactions involved in this preparative route can be monitored by using ATR-FTIR spectroscopy on a single bead. The target compounds, obtained by using this five-step sequence, are produced in high yields and purities.

Concise Synthetic Approaches to Naturally Occurring β-Hydroxypyranochalcones: First Total Synthesis of Purpurenone, Its Derivative, and Praecansone B

  • Wang, Xue;Lee, Yong-Rok;Kim, Sung-Hong
    • Bulletin of the Korean Chemical Society
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    • v.33 no.8
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    • pp.2647-2650
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    • 2012
  • The total synthesis of biologically interesting ${\beta}$-hydroxypyranochalcones, purpurenone (1), its derivative 2, praecansone B (3), and pongapinone A (4) has been accomplished starting from commercially available 2,4-dihydroxyacetophenone or 6-methoxy-2,4-dihydroxyacetophenone in 3 steps by a convergent strategy through benzopyran formations, O-methylations, and coupling reactions.

Study on Synthesis and Mechanical Properties of $B_4C$ by Self Propagating High Temperature Synthesis Chemical Furnace (SHS 화학로에 의한 $B_4C$ 합성 및 기계적 특성에 관한 연구)

  • Lee, Hyung-Bock;Cho, Duk-Ho;Park, Sung;Le, Jea-Won
    • Journal of the Korean Ceramic Society
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    • v.30 no.8
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    • pp.685-693
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    • 1993
  • Boron cabride was prepared from the mixture of metal boron and graphite powders in Argon atmosphere by Self-propagating High-temperature Synthesis Chemical furnace. The most excellent mechanical properties were in the case that Fe was added as a sintering agent before the synthesis of the B4C in the Chemical furnace. Sintered B4C-5wt% Fe specimen showed the relative density of 95%, of theoretical value, and 3-point-flexural strength of 380MPa.

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Study on Synthesis and Mechanical Properties of (B.Si)C Composite by Self Propagating High Temperature Synthesis Chemical Furnace (SHS 화학로에 의한 (B.Si)C 복합체의 합성 및 기계적 특성에 관한 연구)

  • 이형복;조덕호;이재원
    • Journal of the Korean Ceramic Society
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    • v.32 no.4
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    • pp.413-418
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    • 1995
  • The (B.Si)C composite was prepared form the mixture of metal boron, silicon, and carbon powders in Ar atmosphere by Self-propagating High-temperature Synthesis Chemical Furnace. The characterization of synthesized power and sintered body were investigated. The microstructure of sintered body suggested that SiC boundary was made between B4C grains. The most excellent mechanical properties, the relative density of 95% oftheoretical value, 3 point flexural strength of 360MPa, and fracture toughness of 3.6MN/m3/2 could be obtained in 80wt% B4C-20 wt% SiC composite were obtained.

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Influence of Mechanical Activation on Synthesis of Compounds in B/C-Mg/Al/Ca System

  • Urakaev, F.Kh
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2004.05a
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    • pp.60-65
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    • 2004
  • The possibility of mechano-chemical synthesis and influence of mechanical activation on thermal synthesis of borides and boron carbides of mass-low metals is investigated. The opportunity of mechanochemical synthesis in the mill AGO-2 of such compounds as Al $B_2$and Ca $C_2$ $B_2$is established. Influence of mechanical activation in the mill SPEX 8000 on synthesis of such compound as $Mg_{0.5}$A $l_{0.5}$ $B_2$is shown. Features of synthesis in systems containing metal magnesium are considered.d.d.

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Asymmetric Ring Opening of Epoxides Catalyzed by Novel Heterobimetallic Schiff-Bases Containing Transition Metal Salts

  • Kawthekar, RahulB;Bi, Wentao;Kim, Geon-Joong
    • Bulletin of the Korean Chemical Society
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    • v.29 no.2
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    • pp.313-318
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    • 2008
  • An enantioselective ring opening of racemic terminal epoxides has been achieved by using heterobimetallic cobalt salen complexes with variety of nucleophiles. They were proven to be highly enantioselective and reactive for the synthesis of valuable chiral building blocks in enantio-riched forms up to 98% ee.

Efficient Synthesis of Cylindol A and the Proposed Structure of Cylindol B: The Structure of Cylindol B Still in Question

  • Chang, Jay-Hyok;Nam, Do-Hyun;Shin, Hyun-Ik
    • Bulletin of the Korean Chemical Society
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    • v.29 no.5
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    • pp.1003-1006
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    • 2008
  • Highly efficient syntheses of cylindol A (1) and the proposed structure of cylindol B (2) have been accomplished using common synthetic transformations from symmetrical starting materials 7 and 11, respectively. The latter synthesis revealed that the proposed structure of the natural cylindol B was assigned incorrectly. Isomers of 2 such as 15 and 16 were synthesized as a possible candidate of the natural cylindol B. However, their spectral data also did not match that of the natural cylindol B. Therefore, the structure of the natural cylindol B is yet to be resolved.

An Expeditious Room Temperature Stirring Method for the Synthesis of Isoxazolo[5,4-b]quinolines

  • Niralwad, Kirti S.;Shingate, Bapurao B.;Shingare, Murlidhar S.
    • Journal of the Korean Chemical Society
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    • v.55 no.5
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    • pp.805-807
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    • 2011
  • The synthesis of different derivatives of isoxazolo[5,4-b]quinoline by the cyclization reaction of various substituted oximes of quinoline using mild base at ambient temperature. The formation of isoxazolo[5,4-b]quinoline, as a consequence of cheaper and more readily available $K_2CO_3$ and DMF participating in the reaction, is documented.