===============================================================================제 목 : Development and Mechanistic Understanding of Transition Metal-Catalyzed C-C Bond Forming Reactions연 사 : 신광민 박사(MIT)일 시 : 2019년 10월 24일(목) 오후 4시 30분장 소 : 화학관 2층 서병인강의실 (330226호실)================================================================================ Development and Mechanistic Understanding of Transition Metal-Catalyzed C-C Bond Forming ReactionsKwangmin ShinDepartment of Chemistry, Massachusetts Institute of Technology (MIT)The development of new transition metal catalysis for the construction of carbon-carbon bonds has a great impact on broad research fields such as organic synthesis, medicinal and materials chemistry. Here, I present my research effort in recent years toward the establishment of site-selective and/or stereoselective C-C bond forming reactions catalyzed by transition metal complexes. The first part of this talk will describe the development of site-selective Ir(III)-, Rh(III)- and Ru(II)-catalyzed oxidative C-H arylation reactions.[1-3] Mechanistic investigations of these arylation reactions, including isolation, CV and EPR studies of the key reaction intermediates and DFT calculations, will be discussed in detail. In the second part of this talk, the development of copper-hydride catalyzed stereoselective allylation of aldehydes with unactivated 1,3-dienes will be discussed. The effect of kinetic control (slow addition of aldehyde) on the chemo- and stereoselectivity of this allylation reaction will be explained. References Shin, K.; Park, S.-W.; Chang, S.* J. Am. Chem. Soc.2015, 137, 8584. Shin, K.; Park, Y.; Baik, M.-H.*; Chang, S.* Nat. Chem. 2018, 10, 218-224. Kim, J.†; Shin, K.†; Jin, S.; Kim, D.; Chang, S.* J. Am. Chem. Soc.2019, 141, 4137-4146. (†contributed equally) Li, C.†; Shin, K.†; Liu, R.Y.; Buchwald, S. L.* Angew. Chem., Int. Ed.2019, DOI: 10.1002/anie.201911008. (†contributed equally
===============================================================================제 목 : Development of new strong Brønsted acids and their application towards the synthesis of enantio-enriched O-heterocycles연 사 : 이성기 교수(Dept. of Emerging Material Science, DGIST)일 시 : 2019년 10월 10일(목) 오후 4시 30분장 소 : 화학관 2층 서병인강의실 (330226호실)================================================================================ Development of new strong Brønsted acids and their application towards the synthesis of enantio-enriched O-heterocyclesSunggi Leesunggi.firstname.lastname@example.org Since the Akiyama and Terada groups reported chiral phosphoric acids as powerful catalysts in multiple asymmetric functional group transformations, various new Brønsted acids were introduced. Recently, we developed new class of strong Brønsted acids which can provide excellent catalytic activity and well-defined active sites at the same time.1,2 The new catalysts, imidodiphosphorimidates (IDPs), enable multiple transformations which were not possible with conventional organo- and transition-metal catalysts. The handling of cyclic aliphatic oxocarbenium ions in enantioselective reactions is the one of such challenges. Now, the enantioselective carbon-carbon bond formation on these highly reactive and small intermediates can be carried out using IDPs affording O-heterocycles bearing multisubstituted stereogenic centers.3,4 Various lactol acetates reacted with enol silanes in the presence of powerful pre-Lewis acid organocatalysts to furnish the desired oxygen heterocycles with high enantioselectivities. Additionally, 1,4- and 1,5-dicarbonyl compounds were transformed to multisubstituted O-heterocycles via catalytic chemo- and enantioselective additions of silyl nucleophiles. ReferencesKaib, P. S.; Schreyer, L.; Lee, S.; Properzi, R.; List, B. Angew. Chem. Int. Ed.2016, 55, 13200-13203. Lee, S.; Kaib, P. S.; List, B. Synlett2017, 28, 1478-1480.Lee, S.; Kaib, P. S.; List, B. J. Am. Soc. Chem. 2017, 139, 2156-2159.Lee, S.; Bae, H. Y.; List, B. Angew. Chem. Int. Ed.2018, 57, 12162-12166.
================================================== 제 목 : Extremely Active Chiral Catalysts for Challenging Chemical Reactions 연 사 : 배한용 교수님(성균관대학교 화학과)일 시 : 2019년 9월 5일(목) 오후 4시 30분장 소 : 화학관 2층 서병인강의실 (330226호실)================================================== Extremely Active Chiral Catalysts for Challenging Chemical Reactions Hanyong BaeDepartment of Chemistry, Sungkyunkwan University2066, Seobu-ro, Jangan-gu, Suwon, 16419 Korea E-mail: email@example.comVisit our webpage: https://hanyongbae.wixsite.com/hbcatalysis Since its establishment as a field at the beginning of this century, organocatalysis has significantly advanced chemical synthesis in academia and industry. However, a common view suggesting that organocatalysts are generally less active than metal-based catalysts and enzymes still occasionally persists.In this talk, we will discuss our recent findings on biomimetic enantioselective reactions regarding efficient "direct" introduction of (thio)ester enolate equivalents via chiral Brønsted base catalysis. In the light of both mechanistic and environmental approaches, we developed different hydrogen bonding promoted asymmetric reactions that those are, decarboxylative aldol reaction of malonic acid half thioester with aldehyde which is inspired by polyketide biosynthesis, rate-accelerated Michael addition reaction of malonate with nitroolefin “on water” due to the hydrophobic amplification effect, and Mannich reaction of highly reactive thioester enolate precursor dithiomalonate with N-Boc imine/α-amido sulfone. The low catalytic activity, which is regarded as an intrinsic limitation of organocatalyst, could be addressed by taking advantage of nature's solution.As an “in-direct” approach, we will demonstrate a new class of chiral catalysts which enable the highly challenging enantioselective Mukaiyama aldol reaction of ketones in the presence of extremely low catalyst loading (down to 0.00009 mol%: 900 parts-per-billions, ppb). The developed highly acidic (pKa = 4.5 in acetonitrile) imidodiphosphorimidate catalysts were employed as potent catalysts for the Mukaiyama aldol reaction of commercially available silyl ketene acetals with ketones, via Lewis acid catalysis. Previously developed chiral disulfonimides (pKa = 8.4 in acetonitrile), which proved to be efficient catalysts of the Mukaiyama aldol reaction of aldehyde failed to achieve the desired transformation.[4,5] References H. Y. Bae, J. H. Sim, J. W. Lee, B. List, C. E. Song, Angew. Chem. Int. Ed.2013, 52, 12143. H. Y. Bae, C. E. Song, ACS Catal. 2015, 5, 3613. H. Y. Bae, M. J. Kim, J. H. Sim, C. E. Song, Angew. Chem. Int. Ed. 2016, 55, 10825. H. Y. Bae, B. List, Chem.-Eur. J. 2018, 24, 13767. H. Y. Bae, D. Höfler, P. S. J. Kaib, P. Kasaplar, C. K. De, A. Döhring, S. Lee, K. Kaupmees, I. Leito, B. List, Nature Chemistry2018, 10, 888.
===============================================================================제 목 : Transmission Electron Microscope Toward Atomic Structure and Dynamics of Molecules연 사 : 유병국 박사(California Institute of Technology)일 시 : 2019년 8월 29일(목) 오후 4시 30분장 소 : 화학관 2층 서병인강의실 (330226호실)================================================================================ Transmission Electron Microscope Toward Atomic Structure and Dynamics of MoleculesPresenter: Dr. Byung-Kuk Yoo1 (California Institute of Technology)Structure of molecules is the determiner of their properties. Transmission Electron Microscope (TEM) has versatile advantages for scientists thanks to its atomic spatial resolution. As a CryoEM method, micro electron-diffraction (MicroED) has determined a variety of macromolecules with sub-Angstrom resolution until very recently. Moreover, this technique has been further advanced to address the broad needs in structure determination of small molecules. In the first part of the presentation, how MicroED is used to determine the atomic structure of an inorganic molecule will be demonstrated. A heterometallic Mn/Ca cluster (Mn4CaOn) is a synthetic model compound for oxygen-evolving complex of the natural enzyme: photosystem II, which has been vigorously studied as an important biological water oxidation catalyst. Having powder samples of this molecule directly from the synthesis, we were able to collect suitable crystallographic data from nano- and micro-crystals as a movie while the crystals are continuously rotated and solved the structure in atomic resolution in minutes. Our results prove that MicroED is ideal to determine structures for (in)organic chemists in the fields of drug discovery with minimal crystallization trials.In the second part of the talk, I explore TEM as an in-situ tool in pursuit of understanding dynamics. Unlike the conventional TEM, femtosecond time-resolved TEM has a time resolution that is 10 orders of magnitude better than that of TEM. Instead of using thermionic electrons in TEM, laser-driven single pulses of electrons allow various modes of detection such as imaging, diffraction, and spectroscopy, all with unprecedented spatiotemporal resolution; sub-nanometer and femtosecond. I will discuss the development of 4D Ultrafast EM and summarize the up-to-date accomplishments that represent its broad capability in chemical, materials, and biological sciences. As one of those examples, I will introduce how this technique provides a structural dynamic probe for catalytic active site in photocatalytic materials and visualizes the femtosecond atomic movement at the titanium active center in a single-site photocatalyst. Our findings contribute fundamental insights for developing advanced photocatalysts and suggest broad ranges of applications in materials science.1 Staff Scientist @Howard Hughes Medical Institute Research Laboratory, Broad Center for the Biological SciencesDivision of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA
===================================================================================== 제 목 : Chemical Synthesis and Catalysis Harnessing Organosilanes연 사 : 전준하 교수(Department of Chemistry & Biochemistry University of Texas Arlington)일 시 : 2019년 8월 7일(수) 오후 4시장 소 : 화학관 2층 서병인강의실 (330226호실)===================================================================================== Chemical Synthesis and Catalysis Harnessing OrganosilanesJunha JeonDepartment of Chemistry and Biochemistry The University of Texas at ArlingtonArlington, Texas 76019 E-mail: firstname.lastname@example.orgEnvironmentally benign, stable, and abundant organosilanes are increasingly utilized in an impressively wide range of synthetic applications involving biomedically relevant agents, catalysts, and drug delivery vehicles. Despite the advances on organosilane chemistry, much less success has been achieved on broadly applicable, highly regio-, stereo-, and chemoselective silylation of unactivated C–C and C–H bonds. The goals of our research research program are to develop highly efficient synthetic methods for preparation of high-value synthetic building blocks and bioactive molecules and to advance our understanding of the associated catalytic mechanisms. Success in these endeavors will accelerate the use of a variety of novel small molecules to be employed in drug discovery and development, thus contributing to the promotion of human health. In this talk, our efforts toward expanding the dimension of organosilicon chemistry directed toward chemical synthesis and catalysis will be presented. Specifically, the progress on design and application of redox neutral and oxidative C–C and C–H silylation methodologies harnessing a traceless hydrosilyl acetal and our new discovery on catalytic hydrogen atom transfer from hydrosilanes to vinylarenes for hydrosilylation and polymerization will be discussed.
세미나가 취소되었습니다.===================================================================================== 제 목 : MOLECULAR ASPECTS OF FRICTION BETWEEN POLYMER COATED SURFACES연 사 : Prof. Andra Dėdinaitė일 시 : 2019년 6월 18일(화) 오전 11시장 소 : 화학관 2층 서병인강의실 (330226호실)===================================================================================== MOLECULAR ASPECTS OF FRICTION BETWEEN POLYMER COATED SURFACES-the biolubrication perspective Andra Dėdinaitė KTH Royal Institute of Technology, School of Engineering Sciences in Chemistry, biotechnology and Health, Department of Chemistry, Surface and Corrosion Science, Drottning Kristinas väg 51, SE-10044 Stockholm, Sweden Nature has developed aqueous lubrication systems that perform close to perfect for many years under demanding conditions – sudden transitions from stagnant state to motion, shear under high loads and low speeds. These systems operate well lubricated and with minimal wear, if lucky, over 100 years. There is a need to look in detail at nature’s solutions in order to gain understanding of how man-made aqueous lubrication ought to be designed. With this purpose, we consider the complexity of a human synovial joint, joint lubricating fluids, architecture of individual components in these fluids and association structures. Next, we make attempts to mimic the nature and to understand principles of its operation in terms of friction control between surfaces. In order to do so we need to understand self-assembly at interfaces, and lubrication properties of key structural elements – bottle-brush and brush-on-brush polyelectrolytes, as well as polyelectrolye- surfactant aggregates. Examples will be discussed of how synthetically derived analogues of naturally available polyelectrolytes perform in aqueous environment as lubricating agents on solid surfaces. It will also be shown how extremely high friction forces between surfaces, induced between two negatively charged surfaces by oppositely charged polyelectrolyte bridging, can be modified by polyelectroyte association with the surfactant, leading to extremely low friction, even in presence of high adhesive force. Further, the case will be discussed when friction between the surfaces is high despite the absence on adhesion. For good lubrication, strong attachment of lubricant to surfaces is of importance. Thus polymers that contain blocks that lubricate and other blocks that provide strong anchoring to surfaces are desirable. To this end, we have, together with co-workers in Vilnius University, Lithuania, synthesized polyelectrolytes that carry resemblance to muscle-adhesive proteins and demonstrated how thin layers of these polyelectrolytes can withstand harsh attempts off wear without yielding to it.
[Plenary Seminar] 류덕희 회장님 "성취의 삶을 위한 제언"======================================연 사 : 류덕희 회장님(화학과 56학번, 경동제약 회장)제 목 : 성취의 삶을 위한 제언일 시 : 2019년 5월 16일(목) 오후 4시 15분 장 소 : 화학관 1층 첨단강의실(330118호)-------------------------------------- <연사 약력>1. 성명: 류덕희(화학56)2. 소속: 경동제약(주) 회장3. 학력: 1956년 성동공업고등학교 졸업 1956년 성균관대 화학과 입학(61년 졸업) 2001년 성균관대 경영학 명예박사4. 경력: 1960년 성균관대 학생위원장 1960년 4.19 의거 학생대책위원회 성균관대 대표 1996년 한국 천주교 평신도 사도직 협의회 회장 2010년 제8대 한국제약협회 이사장
===================================================================================== 제 목 : Organic Synthesis in Automated Flow Chemistry Platform연 사 : 황예진 교수(인하대학교 화학공학과)일 시 : 2019년 5월 10일(금) 오전 11시-12시장 소 : 화학관 2층 서병인강의실 (330226호실)===================================================================================== Organic Synthesis in Automated Flow Chemistry Platform Ye-Jin Hwang Assistant Professor Department of Chemical Engineering, Inha University, Incheon email@example.com There is increasing pressure in drug discovery to deliver a steady stream of active compounds for physicochemical profiling and potency testing. In order to accelerate lead optimization, it is imperative to reduce the time required for each iteration of design, synthesis, and screening. I will present an automated chemistry platform that can efficiently screen a wide range of reactions, including single/multi-phase, single/multi-step, and photochemical reactions at the 14 microliter scale. Individual droplets are prepared by a liquid handler and moved through fluoropolymer tubing by a carrier gas at elevated pressures. Reactions occur in a heated reactor where the liquid droplet is oscillated back and forth to ensure thorough mixing – even for biphasic liquid-liquid reactions or liquid-gas reactions – without being limited to a finite residence time. Optional inlet and/or outlet injections enable multistep chemistry. A portion of the crude product mixture is sampled and sent directly to an online HPLC/MS for analysis, purification, and product collection, typically of 10-500 μg. The system offers the enhanced heat and mass transfer characteristics, increased safety, and opportunity for automation associated with flow chemistry while enabling the following key advantages: (a) reduction of material consumption, preparing just 40 microliters for each reaction condition, (b) elimination of residence time dispersion, (c) elimination of the inverse relationship between residence time and mass transfer rate for a flow reactor of fixed length, (d) simplification of continuous and discrete variable screening through the use of a liquid handler to prepare reaction mixtures, and (e) elimination of the time- and material-waste associated with waiting for flow reactors to reach steady state. Importantly, because the reaction droplet is equivalent to one segment in a continuous segmented flow, reaction conditions identified using the platform can be directly translated to a continuous synthesis. This helps bridge the connection between the early research stages of drug discovery and the later stages, where material demands grow from the μg-mg scale to the g-kg scale.
================================================================제 목 : A Molecular Design Principle of Purely Organic PHotocatalysts for Visible-light Driven Polymerizations and Organic Reactions연 사 : 권민상 교수(UNIST 신소재공학부)일 시 : 2019년 4월 23일(화) 오후 4시 장 소 : 화학관 1층 첨단강의실(330118호실)================================================================A Molecular Design Principle of Purely Organic PHotocatalysts for Visible-light Driven Polymerizations and Organic Reactions Min Sang Kwon1Department of Materials Science and Engineering Ulsan National Institute of Science and Engineering (UNIST), Ulsan, Korea*E-mail: firstname.lastname@example.org The development of new chemical reactions using photoredox catalysts (PCs) is one of the most important topics in the field of organic and polymer synthesis since photoredox-mediated reactions are “green” and “mild” alternatives to thermal processes, and structurally unusual organic scaffolds can be built under extremely mild conditions using these catalysts. A variety of photoredox-mediated reactions have been actively developed in which organometallic complexes, including Ru(II) and Ir(III), have been mostly employed as PCs. However, concerns about toxicity, cost, precious-metal sustainability, and trace-metal contamination have limited their widespread use, especially in biomedical and electronic applications. In addition, the rather narrow redox-potential ranges and limited structural diversities of these transition-metal complexes limit their scope.Due to their broad structural diversity and benign environmental profiles, purely organic PCs provide attractive alternatives to transition-metal-based catalysts. However, the full potential of organic PCs has not been realized, as the criteria for their design are not well established. Therefore, the development of new transformations using organic PCs is limited to a few organic dyes commonly used for imaging purposes and whose parameters are not straightforwardly tuned through structural alternation.In this talk, we propose a general strategy for the design of purely organic PCs. Strongly twisted donor–acceptor structures are introduced as a general scaffold design for these PCs. The charge transfer (CT) characteristics of the lowest excited states of the designed PCs greatly promote the generation of the lowest triplet excited states (T1) and allow systematic control of the essential catalyst parameters over broad ranges, thereby facilitating efficient catalytic performance. Through combined computational and experimental studies, we provide a flow chart that facilitates the computationally directed rational design of organic PCs for the development of new photoredox-mediated reactions. Based on this strategy, highly efficient organic PCs were discovered that addressed important issues associated with photoredox-mediated atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT), and dehalogenation reaction.  Singh, V. K., Yu, C., Badgujar, S., Kim, Y., Kwon, Y., Kim, D., Lee, J., Akhter, T., Thangavel, G., Park, L. S., Lee, J., Nandajan, P. C., Wannemacher, R., Milian-Medina, B., Luer, L, Kim, K. S.*, Gierschner, J.* & Kwon, M. S.*Nat. Catal.1, 794-804 (2018) “Highly efficient organic photocatalysts discovered via a computer-aided-design strategy for visible-light-driven atom transfer radical polymerization”
<Plenary Seminar>======================================연 사 : 강헌 교수님(서울대학교 화학과)제 목 : 얼음화학일 시 : 2019년 4월 4일(목) 오후 4시 15분 장 소 : 화학관 1층 첨단강의실(330118호)-------------------------------------- 지난 수 세기 동안 화학 연구는 액상의 물에서 진행되는 화학반응에 관심이 집중돼 온 반면, 얼음의 화학은 과학자들의 관심 밖이었다. 그 이유는 지구상에는 물이 얼음보다 많고 지구의 생태계는 물은 기반으로 이루어지기 때문이다. 또한, 온도가 낮은 고체상에서는 원자나 분자의 움직임이 매우 느리고 화학 반응도 일어나지 않는다는 것이 상식이었다. 하지만 우주 전체적으로 보면, 우주의 평균 온도는 대단히 낮고 대부분의 물 분자는 액체보다는 고체상의 얼음 형태로 존재한다. 따라서 우주에 떠다니는 차가운 얼음 입자에서도 끊임없이 원자와 분자가 만나 화학반응을 일으키고, 이렇게 오랜 시간에 걸쳐 생명의 기원에 필요한 분자들이 만들어져 왔을 것이라 과학자들은 상상한다. 본 세미나에서는 얼음에서 일어나는 미지의 화학 과정에 대한 연구를 간략히 소개한다. 실험실에서 고진공 표면 분광분석 장비를 사용하여 얼음 화학에 대한 어떠한 연구를 수행할 수 있으며, 얼음 화학의 지식이 저온 환경에서 일어나는 화학과정 및 우주의 얼음 입자에서의 분자 생성 과정을 밝히는 연구에 어떻게 활용될 수 있는지를 논의한다.