https://scholar.dgist.ac.kr/handle/20.500.11750/12074 Thu, 04 Jun 2026 00:34:42 GMT 2026-06-04T00:34:42Z https://scholar.dgist.ac.kr/handle/20.500.11750/60366 Title: Spectroscopic Evidence of a Reduced Alkenylnickel Intermediate in Catalytic Markovnikov-Selective Alkyne Hydroboration Author(s): Lee, Jeong Woo; Kim, Gun Ha; Jeong, Seo Yeong; Jeon, Ji Hwan; Kwon, Hyejin; Kim, Yung Sam; Jung, Byunghyuck; Seo, Sangwon; Rohde, Jan-Uwe; Hong, Sung You Abstract: Nickel-catalyzed hydrofunctionalization reactions, including the hydroboration of alkynes, have been generally proposed to proceed via classical two-electron pathways or, alternatively, through a NiIH-based insertion mechanism. Despite efforts to discern these pathways, explicit spectroscopic observation of NiIH species and relevant mechanistic information on LNiI(alkenyl) species remain lacking. Herein, we provide experimental evidence of formal NiI intermediates, suggestive of a NiIH-based insertion mechanism for alkyne hydroboration. The formation of a NiI catalyst precursor, LnNiI(dpm) (dpm = dipivaloylmethanate anion) and an LnNi(alkenyl) intermediate was confirmed by EPR spectroscopy and HRMS analysis. Their involvement in the catalytic reaction was demonstrated by stoichiometric and catalytic reactivity studies. The origin of the counterintuitive Markovnikov selectivity in the formation of the α-alkenylboronate product was probed by systematic ligand electronic effect studies. Computational analyses rationalize the selectivity by a kinetic preference for formation of the α regioisomer of the LnNi(alkenyl) intermediate through noncovalent interactions. Tue, 31 Mar 2026 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/60366 2026-03-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/60350 Title: Cu-Catalyzed Stereo- and Regioselective Diborylation and trans-Protoborylation of 1,3-Enynes Author(s): Lee, Yeonjoo; Kim, Minseop; Lee, Dohun; Lee, Yunmi; Seo, Sangwon; Jung, Byunghyuck Abstract: As multifunctional chemical tools, organodiboron compounds present an important challenge in organic synthesis, with respect to their synthesis and functionalization. Although readily available 1,3-enynes have been employed as a platform for various regioselective difunctionalization reactions, the diborylation reactions of 1,3-enynes remain limited, and the installation of a CF3 group is often a prerequisite. In this study, we report a copper-catalyzed selective diborylation reaction of 1,3-enynes to access synthetically useful 1,1- and 1,4-diborylalkenes. The synthetic utility of this method is demonstrated by a gram-scale synthesis of a natural antifouling agent. Furthermore, the Cu-catalyzed trans-protoborylation reaction of aryl-substituted (Z)-enynes is reported. The thorough computational studies and the deuterium-labeling experiments provide insights into the reaction mechanism and the regio- and stereoselectivity of diborylated products. Sat, 28 Feb 2026 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/60350 2026-02-28T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/58586 Title: Regioselective Transformations of Unsaturated Systems Catalyzed by Low-Valent Nickel: Cycloaddition, Hydrosilylation, and Dicarbofunctionalization Author(s): Kim, Gun Ha; Jeon, Ji Hwan; Jung, Byunghyuck; Rohde, Jan-Uwe; Hong, Sung You Abstract: In this Account, we describe our recent research progress in the development of the functionalization of unsaturated substrates catalyzed by low-valent nickel. In particular, we discuss nickel-catalyzed azide–alkyne cycloaddition (NiAAC), [2 + 2 + 2] cycloaddition of diynes and nitriles, hydrosilylation of alkynes, and dicarbofunctionalization of 1,3-enynes. Moreover, we highlight our mechanistic studies aimed at elucidating catalytically active nickel intermediates, thereby contributing to the understanding and expansion of nickel-catalyzed synthetic methodologies. © 2025. Thieme. All rights reserved. Thu, 31 Jul 2025 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/58586 2025-07-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/58224 Title: Synthesis of (Z)-Allylsilanes by Cu-Catalyzed Regioselective Protosilylation of Allenes via a Single-Electron Process Author(s): Kim, Min; Kim, Seongha; Lee, Yurim; Lee, Yunmi; Seo, Sangwon; Jung, Byunghyuck Abstract: Hydrosilylation of allenes has gained prominence as an economically viable method for preparing vinylsilanes or allylsilanes. However, development of transition metal (TM)-catalyzed hydrosilylation remains challenging owing to the difficulty in controlling the regioselectivity and stereoselectivity. Specifically, access to (Z)-allylsilanes via first-row TM-catalyzed hydrosilylation is limited by the lack of mechanistic diversity, indicating the need for unprecedented approaches to achieve this valuable yet underexplored chemical space. We herein present the Cu-catalyzed protosilylation of allenes in either organic solvent or water, which affords (Z)-allylsilanes in high yields, with up to >98:2 regioselectivity and (Z)-selectivity. In contrast to conventional TM-catalyzed hydrosilylation or Cu-catalyzed protosilylation, our process involves a single-electron pathway for inserting Cu-SiMe2Ph into the allene. Radical trap experiments and systematic computational studies support the proposed mechanism. Our method is gram-scalable, and the synthetic utility is demonstrated by the preparation of deuterium-incorporated (Z)-allylsilanes through reactions in D2O. Tue, 31 Dec 2024 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/58224 2024-12-31T15:00:00Z