Seminar

Seminar

Development of Metal-Catalyzed Direct C-H Amination Reactions

  • POSTED DATE : 2016-11-28
  • WRITER : 관리자
  • HIT : 3387
  • DATE : 2016-12-01
  • PLACE : 화학관 330118호
 

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제  목 :  Development of Metal-Catalyzed Direct C-H Amination Reactions

연  사 :  장석복 교수(KAIST)

일  시 :  2016년 12월 1일(목) 오후 4시 15분   
장  소 :  화학관 첨단강의실(330118호)

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Development of Metal-Catalyzed Direct C-H Amination Reactions


Sukbok Chang


 Institute for Basic Science (IBS), Daejeon 305-701, Korea


Department of Chemistry, Korea Advanced Institute of Science & Technology (KAIST), Daejeon 305-701, South Korea


E-mail: sbchang@kaist.ac.kr


 


The mechanism of the Ir(III) and Rh(III)-mediated C–N coupling reaction, which is the key step of catalytic C-H amidation, was investigated in an integrated experimental and computational study. Novel amidating agents containing a 1,4,2-dioxazole moiety allowed for designing a stoichiometric version of the catalytic C–N coupling reaction and giving access to reaction intermediates that reveal details about each step of the reaction. Both DFT and kinetic studies strongly point to a mechanism where the M(III) complex engages the amidating agent via oxidative coupling to form a M(V)-imido intermediate, which then undergoes migratory insertion to afford the final C–N coupled product. For the first time, the stoichiometric versions of the Ir and Rh-mediated amidation reaction were compared systematically to each other. Iridium reacts much faster than rhodium (~ 1100 times at 6.7 oC) with the oxidative coupling being so fast that the activation of the initial Ir(III)-complex becomes rate-limiting. In the case of Rh, the Rh-imido formation step is rate-limiting. These qualitative difference stems from a unique bonding feature of the dioxazole moiety and the relativistic contraction of the Ir(V), which affords much more favorable energetics for the reaction. For the first time, a full molecular orbital analysis is presented to rationalize and explain the electronic features that govern this behavior.


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[1] S. H. Cho, J. Kim, J. Kwak, Sukbok Chang, Chem. Soc. Rev.2011, 40, 5068-5083


[2] K. Shin, H. Kim, S. Chang, Acc. Chem. Res. 2015, 48, 1040-1052


[3]Y. Park, K. T. Park, J. G. Kim, S. Chang, J. Am. Chem. Soc. 2015, 137, 4534-4542


[4] W. Xie, J. H. Yoon, S. Chang, J. Am. Chem. Soc. 2016, 138, 12605-12614

[5] Y. Park, J. Heo, M.-H. Baik, S. Chang, J. Am. Chem. Soc. 2016, 13