|Speaker||Prof. Seunghoon Shin|
|Date||Thursday 17 November 2016|
|Venue||#331, Asan Hall, College of Science|
“Synthetic Methods Development based on
Rational Analysis of Intermediates”
Proper analysis and identification of reaction intermediates in catalysis often lead to new reaction discovery. In this presentation, we describe some of our recent investigations in the gold and Brőnsted acid catalysis. Allenols are found to be transient intermediates in the gold-catalyzed Meyer-Schuster rearrangement of propargyl alcohols en route to enones. In our tandem Meyer-Schuster rearrangement and ring expansion (eq. 1),1 the allenol intermediates play key roles in the diastereo- and enantioselective ring expansion of cyclobutanols having a butyne-1,4-diol unit into cyclopentanones. A related allenol intermediate could also be utilized in the context of cross-coupling chemistry. Compared to the dual Au-photoredox cross-coupling of C(sp3)-Au intermediates,2a the corresponding cross-coupling of C(sp2)-Au species for the formation of C(sp2)- C(sp2) coupling is more challenging, due to a facile proto-demetallation of C(sp2)-Au bond. The Au(I)-Au(III) cycle enabled under the photoredox condition is fast enough to outcompete this undesired side pathway (eq. 2).2b-c This protocol is catalytic both in gold- and photocatalyst and utilizes diazoniums for the dual role of external oxidant and coupling partner. Lastly, oxygenative cross-coupling of alkynes has received tremendous growth, as it obviates the use of diazo precursors. Yet, a concrete support for the involvement of Au-carbene species is still lacking and, especially, intermolecular coupling is very rare. Using Brőnsted acid as a catalytic promotor instead of Au-complex, this transformation occurs under exceptionally mild conditions allowing couplings of diverse nucleophiles (eq. 3). In addition, a SN2’ mechanism could be supported by the formation of scalemic products when chiral N-oxides were used.
1. An, J. -H.; Yun, H.; Shin, S.; Shin, S., Adv. Synth. Catal. 2014, 356, 3749.
2. (a) Sahoo, B.; Hopkinson, M. N.; Glorius, F. J. Am. Chem. Soc. 2013, 135, 5505; (b) Patil, D. V.; Yun, H.; Shin, S. Adv. Synth. Catal. 2015, 357, 2622; (c) Um, J.; Yun, H.; Shin, S. Org. Lett. 2016,18, 484.
3. Unpublished results, Patil, D. V.; Kim, S.
Prof. Seunghoon Shin
Department of Chemistry, Hanyang University, South Korea
|Notice||Spring semester 2017 Seminar Schedule||-||-|
|32||7th Jilin-Korea-Waseda Alliance Annual Symposium||-||August 17 ~ 19, 2017|
|31||[Wed. 5 July. 2017] Seminar was canceled!||-||-|
|30||[Fri. 16 Jun. 2017] Prof. Martin Thuo/Department of Materials Science and Engineering, Iowa State University, USA||Prof. Martin Thuo||Fri. 16 Jun. 2017|
|29||[Thu. 8 Jun. 2017] Prof. Won-jin Chung/Department of Chemistry, GIST, Gwangju, Republic of Korea||Prof. Won-jin Chung||Thu. 8 Jun. 2017|
|28||[Thu. 1 Jun. 2017] Prof. Jong-Man Kim/Department of Chemical Engineering, Hanyang University, Seoul, Korea||Prof. Jong-Man Kim||Thu. 1 Jun. 2017|
|27||[Thu. 25 May. 2017] Prof. Wonsuk Kim/Department of Chemistry and Nano Science, Ewha Womans University, Seoul||Prof. Wonsuk Kim||Thu. 25 May. 2017|
|26||[Thu. 18 May. 2017] Student Host Colloquium : 1,1-Bisborylalkane: New Class of Organoboron Compound for the Chemo, Regio and Stereoselective Organic Transformations||Prof. Seung Hwan Cho||Thu. 18 May. 2017|
|25||[Thu. 11 May. 2017] Prof. Andreas Heinrich/IBS Research, Center for Quantum Nanoscience, Seoul, South Korea||Prof. Andreas Heinrich||Thu. 11 May. 2017|
|24||[Thu. 27 Apr. 2017] Seminar was canceled!||-||-|
|23||[Thu. 13 Apr. 2017] Dr. Wan Ki Bae/Photoelectronic Hybrid Research Center, Korea Institute of Science and Technology, Seoul, Korea||Dr. Wan Ki Bae||Thu. 13 Apr. 2017|
|22||[Thu. 6 Apr. 2017] Prof. Rong-Jie Chein/Institute of Chemistry, Academia Sinica, Nankang, Taipei, Taiwan||Prof. Rong-Jie Chein||Thu. 6 Apr. 2017|
|21||[Thu. 30 Mar. 2017] Prof. Jeong Ho Cho/SKKU Advanced Institute of Nanotechnology (SAINT), School of Chemical Engineering, Sungkyunkwan University, Suwon, Korea||Prof. Jeong Ho Cho||Thu. 30 Mar. 2017|
|20||[Thu. 23 Mar. 2017] Prof. Sangsu Bae/Department of Chemistry, Hanyang University, Seoul, South Korea||Prof. Sangsu Bae||Thu. 23 Mar. 2017|
|19||[Fri. 17 Mar. 2017] 9th RINS Symposium||-||Fri. 17 Mar. 2017|
|18||[Thu. 9 Mar. 2017] Prof. Woon Ju Song/Department of Chemistry, Seoul National University, Seoul, Korea||Prof. Woon Ju Song||Thu. 9 Mar. 2017|
|17||[Mon. 9 Jan. 2017] Prof. Sungwook Woo/Wyss Institute for Biologically Inspired Engineering, Harvard University, USA||Prof. Sungwook Woo||Mon. 9 Jan. 2017|
|16||[Wed. 28 Dec. 2016] Prof. James Y. Hamilton/Development of a Broad Range of Asymmetric C–C Bond Forming Reactions with a Versatile Iridium Catalyst||Prof. James Y. Hamilton||Wednesday 28 December 2016|
|15||[Thu. 1 Dec. 2016] Prof. Sang-Yong Ju/Highly Pure Carbon Nanotubes sorted by a Flavin for Thin Film Transistor Applications||Prof. Sang-Yong Ju||Thursday 1 December 2016|
|»||[Thu. 17 Nov. 2016] Prof. Seunghoon Shin/Synthetic Methods Development based on Rational Analysis of Intermediates||Prof. Seunghoon Shin||Thursday 17 November 2016|
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