Friday, March 29, 2019 3:30 p.m. to 5:45 p.m.

Transition Metal-Catalyzed Alkyne Functionalization for Use in Organic Synthesis

Abstract:  Transition metals interact with alkynes to generate s-alkynyl, p-alkyne and vinylidene complexes that exist in dynamic equilibrium with one another.1 Our laboratory has been engaged in the development of new synthetic methods that make use of alkynes via mechanisms involving a metal vinylidene as a catalytic intermediate. A diverse array of new reactions has been developed, including enyne cycloisomerizations, and various processes effecting hydrative, alkylative, and carboxylative cyclizations (Fig. 1). Recently, in a departure from these C-C bond-forming cyclizations, our explorations have been focused on the oxygen-transfer to the metal-bound carbene intermediate. This approach has led to discovery of alkyne oxygenation that occurs through the intermediacy of a metalloketene arising from catalytic oxidation of the metal vinylidene. Discussed in this presentation will be the design, implementation and mechanistic studies of the metal vinylidene-mediated catalytic oxygenative reactions of alkynes. Also presented will be a tandem addition–cyclization–rearrangement process, in which alkyne-tethered hydrazones react with organoboronic acids to give cycloalkene products in a traceless fashion based on the merger of pericyclic rearrangement and transition metal catalysis making use of a p-alkyne intermediate. The novel cascade process can also be performed with enantiocontrol. Employing a chiral diene ligand for the rhodium catalyst, the reaction provides cycloalkenes possessing an exo stereocenter with high enantioselectivity.2

Bio:  Chulbom Lee went to Seoul National University to receive B.S. (1988) and M.S. (1990) degrees in Chemistry under the direction of Professor Eun Lee. After brief stays in the Korean Army and the Institute for Basic Sciences of SNU in 1992, he proceeded to Stanford University to work with Professor Barry M. Trost for his Ph.D. studies as national merit scholar of Ministry of Education. In 1998, he moved to Memorial Sloan-Kettering Cancer Center at New York to work with Professor Samuel J. Danishefsky as US Army Breast Cancer Research Postdoctoral Fellow. Upon completing his postdoctoral studies in 2001, he joined the faculty of the Chemistry Department of Princeton University as Assistant Professor. In 2008, he moved back to his alma mater, SNU, and has remained there as Professor of Chemistry. He has served as Associate Chair of the department (2013-15), SNU Faculty Senator (2015-16), Vice President of the Korean Chemical Society (2014) and the Korean Society of Organic Synthesis (2012), and review board member of the National Research Foundation of Korea (2015-16). He is currently Associate Editor of Organic Chemistry Frontiers (RSC) and on the advisory board of Chemical Reviews (ACS), while serving as Chair of the KCS International Committee, EXCO member of FACS (Federation of Asian Chemical Societies) and IUPAC committee (Div. VII). He was a recipient of the Roche Award (1998), the U.S. Army Postdoctoral Fellowship (1999-2001), the Thieme Journal Award (2001), the Amgen Young Investigator Award (2006), the SNU Teaching Award (2011), Samsung Foundation Grant (2014), and Chang Sehee Award (2015) of the KCS. His research is focused on the development of novel methods and strategies for organic synthesis. In particular, his group has been engaged in the design, implementation and mechanistic elucidation of new chemical reactions that occur through transition metal catalysis. His research is also concerned with the synthesis of natural products possessing complex molecular architectures and significant biological activities.

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HEC 125: 125

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chemistry Organic Chemistry Organic Synthesis Chemistry Seminar