Ki Seong Kim

Bio: Ki Seong Kim is an academic researcher from Hanyang University. The author has contributed to research in topics: Palladium & Catalysis. The author has an hindex of 3, co-authored 7 publications receiving 174 citations.

The Palladium-Catalyzed Addition of Organoboronic Acids to Alkynes†

Abstract: [*] Prof. Dr. C. H. Oh, H. H. Jung, K. S. Kim, N. Kim Department of Chemistry Hanyang University Sungdong-Gu, Seoul 131-791 (Korea) Fax: (+82)2-2299-0762 E-mail: changho@hanyang.ac.kr [**] We wish to acknowledge the financial support of KOSEF (2001-1123-001-5) and the Center for Molecular Design and Synthesis (CMDS, R11-1999-05601). Supporting information for this article is available on the WWW under http://www.angewandte.org or from the author. Angewandte Chemie

New aspects on the superplasticity of fine-grained 7475 aluminum alloys

Abstract: Thermomechanical processes were developed which give fine grain sizes of 6 and 8 μm in the 7475 Al alloy. Superplastic properties of this material were evaluated in the temperature range of 400 °C to 545 °C over the strain-rate range of 2.8 x 10-4 to 2.8 X 10-2 s-1. The maximum ductility exhibited by the alloy was approximately 2000 pct, and optimum superplasticity was achieved at a strain rate of 2.8 X 10-3 s-1 which is higher by an order of magnitude than other 7475 Al alloys. This result is attributed to the presence of fine dispersoids which maintain the fine grain size at high homologous temperatures. The flow stress and strain-rate sensitivity strongly depend on the grain size. The superplastic 7475 Al alloy has strain-rate sensitivities of 0.67 (6 μm) and 0.5 (13 μm) and an activation energy which is similar to the one for grain boundary diffusion of aluminum. Microstructural investigation after superplastic tests revealed zones free of dispersoid particles at grain boundaries primarily normal to the tensile direction. These dispersoidfree zones (DFZs) appear even after 100 pct elongation and are occasionally as large as 5 μm across. This result demonstrates the importance of diffusional flow in superplastic deformation of the fine-grained 7475 Al alloy especially at low elongations.

Pd-catalyzed addition of organoboronic acids to alkynes at room temperature

Abstract: Combination of Pd(OAc) 2 with 2-bromo-1,3-bis-[diphenylphosphenomethyl)]benzene (1) or 2-bromo-1,3-bis-[di-tert-butylphosphenomethyl)]benzene (3) catalyzed hydroarylations and hydroalkenylations of various alkynes more efficiently in terms of reaction time and temperature.

Pd-Catalyzed Addition of Organoboronic Acids to Alkynes at Room Temperature.

Abstract: Combination of Pd(OAc) 2 with 2-bromo-1,3-bis-[diphenylphosphenomethyl)]benzene (1) or 2-bromo-1,3-bis-[di-tert-butylphosphenomethyl)]benzene (3) catalyzed hydroarylations and hydroalkenylations of various alkynes more efficiently in terms of reaction time and temperature.

Synthesis of heterocycles via transition-metal-catalyzed hydroarylation of alkynes

Abstract: Transition-metal (TM)-catalyzed hydroarylation reactions of alkynes have received much attention, because they enable the net insertion of alkyne C-C triple bonds into C-H bonds of aromatic precursors, resulting in regio- and stereo-selective formation of synthetically useful arylalkenes. Taking advantage of this feature, TM-catalyzed alkyne hydroarylations have been successfully used for the synthesis of heterocycles. TM-catalyzed alkyne hydroarylations can be classified into three major categories depending on the type of reaction and precursors involved: (1) palladium-catalyzed reductive Heck reactions of alkynes with aryl halides, (2) TM-catalyzed conjugate arylation reactions of activated alkynes with arylboronic acids, and (3) TM-catalyzed aromatic C-H alkenylations with alkynes. This review surveys heterocycle synthesis via TM-catalyzed hydroarylation of alkynes according to the above classification, with an emphasis on the scope and limitations, as well as the underlying mechanisms.

Facile regio- and stereoselective hydrometalation of alkynes with a combination of carboxylic acids and group 10 transition metal complexes: selective hydrogenation of alkynes with formic acid.

Abstract: A facile, highly stereo- and regioselective hydrometalation of alkynes generating alkenylmetal complex is disclosed for the first time from a reaction of alkyne, carboxylic acid, and a zerovalent group 10 transition metal complex M(PEt3)4 (M = Ni, Pd, Pt). A mechanistic study showed that the hydrometalation does not proceed via the reaction of alkyne with a hydridometal generated by the protonation of a carboxylic acid with Pt(PEt3)4, but proceeds via a reaction of an alkyne coordinate metal complex with the acid. This finding clarifies the long proposed reaction mechanism that operates via the generation of an alkenylpalladium intermediate and subsequent transformation of this complex in a variety of reactions catalyzed by a combination of Brϕnsted acid and Pd(0) complex. This finding also leads to the disclosure of an unprecedented reduction of alkynes with formic acid that can selectively produce cis-, trans-alkenes and alkanes by slightly tuning the conditions.

Structure, Properties, and Preparation of Boronic Acid Derivatives. Overview of Their Reactions and Applications

Abstract: Structurally, boronic acids are trivalent boron-containing organic compounds that possess one alkyl substituent (i.e., a C–B bond) and two hydroxyl groups to fill the remaining valences on the boron atom (Figure 1.1). With only six valence electrons and a consequent deficiency of two electrons, the sp2-hybridized boron atom possesses a vacant p orbital. This low-energy orbital is orthogonal to the three substituents, which are oriented in a trigonal planar geometry. Unlike carboxylic acids, their carbon analogues, boronic acids are not found in nature. These abiotic compounds are derived synthetically from primary sources of boron such as boric acid, which is made by the acidification of borax with carbon dioxide. Borate esters, the main precursors for boronic acid derivatives, are made by simple dehydration of boric acid with alcohols. The first preparation and isolation of a boronic acid was reported by Frankland in 1860 [1]. By treating diethylzinc with triethylborate, the highly air-sensitive triethylborane was obtained, and its slow oxidation in ambient air eventually provided ethylboronic acid. Boronic acids are the products of the second oxidation of boranes. Their stability to atmospheric oxidation is considerably superior to that of borinic acids, which result from the first oxidation of boranes. The product of a third oxidation of boranes, boric acid, is a very stable and a relatively benign compound to humans (Section 1.2.2.3). Their unique properties as mild organic Lewis acids and their mitigated reactivity profile, coupled with their stability and ease of handling, makes boronic acids a particularly attractive class of synthetic intermediates. Moreover, because of their low toxicity and their ultimate degradation into the environmentally friendly boric acid, boronic acids can be regarded as “green” compounds. They are solids that tend to exist as mixtures of oligomeric anhydrides, in particular the cyclic six-membered boroxines (Figure 1.1). For this reason and other considerations outlined below, the corresponding boronic esters are often preferred as synthetic intermediates. Although other classes of organoboron compounds have found tremendous utility in organic