Seminar

Seminar

Visible Light-Induced Radical Transformations / Iron Catalysis:from High-valent Lewis Acid Catalyst to Low-valent Redox Catalyst

  • POSTED DATE : 2016-12-06
  • WRITER : 관리자
  • HIT : 3564
  • DATE : 2016-12-08
  • PLACE : 화학관 330226호

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<세미나1>


제  목 : Visible Light-Induced Radical Transformations

연  사 : 조은진 교수님(중앙대학교)

일  시 : 2016년 12월 8일(목) 오후 4시

장  소 : 화학관 2층 세미나실(330226호실)


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Visible Light-Induced Radical Transformations


Eun Jin Cho


Department of Chemistry, Chung-AngUniversity, Seoul 06794, Republic of Korea


E-mail:ejcho@cau.ac.kr


Recently, visible light photocatalysis has attracted substantial attention due to its environmental compatibility and mechanistic versatility in promoting a large number of synthetically important reactions. We have developed a variety of radical transformations using Ru-, Ir-, and Pt-based photocatalysts under visible light irradiation.


Fluoroalkylated organic compounds play significant roles in the pharmaceutical, agrochemical, and material sciences owing to the substantial influence that fluorine substitution has on the physical and chemical properties of substances. Visible light-induced methods allowed access to fluoroalkyl group-containing molecules, such as –CF2R, –CF3,and –CF2SPh groups.1 In the studies, electron deficient carbon-centered fluoroalkyl radicals were successfully generated by the appropriate choice of fluoroalkyl source, photocatalyst, additives, and solvent. Notably, we have observed that additives significantly affect the efficiencies and selectivities of these reactions and can even change the outcome of the reaction by playing additional roles during its course. By understanding the roles of additives, we developed several controlled fluoroalkylation reactions of alkenes and alkynes where different products were formed selectively from the same starting substrates.2-4


Polyheteroaromatic compounds have also attracted much attention due to their unique p-conjugation, which make them suitable functional materials in many applications. The synthesis of carbazole motif has been accomplished using N-substituted amidobiaryls through the merger of photoredox and palladium catalysis.5 The use of 1 mol% of an Ir-photocatalyst obviated the typical high loadings of external chemical additives in the transformation. And recently, we synthesized a new class of polyheteroaromatics from the coupling process between readily accessible 2-heteroaryl substituted aromatic amines and heteroaromatic alkynes by an Ir-catalyzed visible light photocatalysis.6


[References]


  1. Chatterjee, T.; Iqbal, N.; You, Y.; Cho, E. J.Acc. Chem. Res. 2016, 49, 2284-2294.

  2. Iqbal, N.; Jung, J.; Park, S.; Cho, E. J. Angew. Chem. Int. Ed. 2014, 53, 539-542.

  3. Yu, C.; Iqbal, N.; Park, S.; Cho, E. J. Chem. Commun. 2014, 50, 12884-12887.

  4. Choi, Y.; Yu, C.; Kim, J. S.; Cho, E. J. Org. Lett. 2016, 18, 3246-3249.

  5. Choi, S.; Chatterjee, T.; Choi, W. J.; You, Y.; Cho, E. J. ACS Catalysis, 2015, 5, 4796-4802.

  6. Chatterjee, T.; Choi, M. G.; Kim, J.; Chang, S.-K.; Cho, E. J. Chem. Commun. 2016, 52, 4203-4206.

     


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<세미나2>


제  목 : Iron Catalysis:from High-valent Lewis Acid Catalyst to Low-valent Redox Catalyst 

연  사 : 강은주 교수님(경희대학교)

일  시 : 2016년 12월 8일(목) 오후 5시

장  소 : 화학관 2층 세미나실(330226호실)


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Iron Catalysis:


from High-valent Lewis Acid Catalyst to Low-valent Redox Catalyst 


 


Eun Joo Kang



e-mail: ejkang24@khu.ac.kr


 


The use of iron compounds as catalysts in organic synthesis is attractive for a number of reasons. It is the most abundant metal in the earth’s crust after aluminum and therefore is much cheaper than the precious metals that are often applied. Regarding the catalytic efficiency and broad applicability, at present iron is still behind palladium as the most versatile catalytic metal, however, the tremendously increasing number of publications demonstrates that iron is catching up. Unlikely palladium, iron can adopt ocidation states from -2 to +5, thus, in low oxidation states it may be operative as an iron-centered nucleophile and catalyze nucleophilic substitutions and additions. In contrast, iron Lewis acid catalyzed reactions have been known for a long time, for example electrophilic aromatic substitutions. Haaving this potential in mind, our lab has been interested in alternative use of iron catalysis in the following organic synthesis.


First, we reported Fe catalyzed atom-economical tandem reaction of alkene-iodide in the present of equimolar aryl Grignard reagent. Aryl Grignard reagent is used to generate Fe-Grignard complex and the counter aryl anion is used in the further cross-coupling, thereby affording the tandem cyclization/cross-coupling radical reaction. Also, the nucleophilic cyclization reactions of allenes were catalyzed by Fe(III) to afford the corresponding heterocycle compound. Fe(III) catalysts were applied in the reactions of allenyl amides or allenyl alcohols and cyclized compounds containing O or N heteroatom were produced with moderate to good yields.


 


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