Three-Component 1,2-Carboamidation of Bridged Bicyclic Alkenes via RhIII-Catalyzed Addition of C-H Bonds and Amidating Reagents.

Transition-metal-catalyzed C-H functionalization is one of the fascinating scientific fronts in organic synthesis for the formation of conjugated arenes and has emerged as a benchmark to revolutionize the synthetic enterprise since past decades. In this realm, chelation-guided functionalization of C-H bonds using an exogenous directing group has received considerable attention recently for the expedient regioselective construction of C-C and C-heteroatom bonds as an efficient and sustainable alternative. This article outlines our contribution towards a wide variety of transformations that have been achieved by the directed C-H functionalization through the fine tuning of catalytic systems.

Transition-Metal-Catalyzed Directing Group Assisted (Hetero)aryl C-H Functionalization: Construction of C-C/C-Heteroatom Bonds.

S,O-Ligand-Promoted Pd-Catalyzed C−H Olefination of Anisole Derivatives

Modulation of the Interfacial Charge Density on Fe2p–Cop by Coupling Ceo2 for Accelerating Alkaline Electrocatalytic Hydrogen Evolution Reaction and Overall Water Splitting

The fundamental understanding of the transition from a homogeneous nanostructure to a heterogeneous one is essential for controllably exploiting the heterostructure catalysts, however, it still remains a challenge. Herein, through simply tailoring the selenization temperature, for the first time we achieve the controllable transition engineering from the homogeneous NiSe2 nanowrinkles (NiSe2 NWs) to heterogeneous Ni3Se4/NiSe2 nanorods (Ni3Se4/NiSe2 NRs) on Ni foam substrate. The unique rod-like nanoarray architecture with high surface roughness can greatly improve the mass transport efficiency. More importantly, the density function theory calculations decipher that the electron redistribution spontaneously takes place at the interfacial region between Ni3Se4 and NiSe2, which could optimize the adsorption/desorption of reaction intermediates and decrease the Gibbs free energy of rate determining step for urea oxidation reaction (UOR). As a consequence, the heterogeneous Ni3Se4/NiSe2 NRs manifests superior UOR performance than its counterpart of homogeneous NiSe2 NWs, especially at large current densities. 

Controllable transition engineering from homogeneous NiSe2 nanowrinkles to heterogeneous Ni3Se4/NiSe2 rod-like nanoarrays for promoted urea-rich water oxidation at large current densities

To design heterojunction electrocatalysts for water splitting in industrial plants, replacing RuO 2 , IrO 2 , and Pt/C remains challenging. We prepared heterostructures of nickel selenide (NiSe) and cobalt-iron layer double hydroxide (CoFe LDH), CoFe LDH@NiSe, using hydrothermal and electrodeposition processes. The interfacial coupling enhanced the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). The CoFe LDH@NiSe required an overpotential of 127 mV and 38 mV for a current density of 10 mA cm −2 with a Tafel slope of 37 mV dec −1 and 33 mV dec −1 for OER and HER in alkaline solutions. Density functional theory calculations showed the enhancement of OER performance. The catalytic activity of CoFe LDH@NiSe increased the electronic conductivity, enhancing the water splitting with 10 mA cm −2 at 1.51 V. The robustness was demonstrated by the long-term stability for 120 h. This study provides a strategy for developing heteronanostructure electrocatalysts for water splitting in fields such as metal-air batteries and energy storage. An interface engineering approach was developed to fabricate NiSe coupled with CoFe LDH in which the hierarchical assembly of heteronanostructured nanosheets exhibited excellent electrocatalytic performance for overall water splitting kinetics. • CoFe-LDH@NiSe nanosheets were prepared by hydrothermal/electrodeposition method. • The mass activity of CoFe-LDH@NiSe surpasses the state-of-the-art electrocatalysts. • DFT proves abundant vacant active sites enhancing the performance of OER. • The designed heteronanostructure exhibits an excellent catalytic performance. 

Designing a smart heterojunction coupling of cobalt-iron layered double hydroxide on nickel selenide nanosheets for highly efficient overall water splitting kinetics

Synthesis of Bidentate Nitrogen Ligands by Rh-Catalyzed C-H Annulation and Their Application to Pd-Catalyzed Aerobic C-H Alkenylation.

Divergent Strategies for the π-Extension of Heteroaryl Halides Using Norbornadiene as an Acetylene Synthon.

The development of ligands and the elucidation of their roles in the catalytic cycle are key to achieving high efficiency and selectivity in nondirected transition-metal-catalyzed C–H functionalization. In particular, careful ligand design can enable the functionalization of previously inaccessible substrate positions, which can lead to regiodivergent transformations of common reactants. In this study, a series of pyrazolopyridone (PzPyOH) ligands that can be easily prepared in a single step was developed for the Pd-catalyzed perdeuteration and meta-selective alkenylation of arenes. In this system, the 2-pyridone moiety was incorporated to function as an internal base, facilitating C–H cleavage and rendering C–H activation reversible, even at challenging sp2 C–H bonds, thus enabling perdeuteration. In addition, the reversible activation of the C–H bonds implies that site selectivity is determined during the migratory insertion step in the alkenylation reaction, thereby preferentially functionalizing the meta-positions rather than the typically more reactive ortho- and para-positions of anisole derivatives. Further, the electronic and structural properties of the pyrazole moiety provide flexibility in the ligand binding to Pd, enabling the facile coordination of an alkene coupling partner during alkenylation. In this process, the hydrogen bonding between pyridone and acetate ligands was crucial to stabilize intermediates, allowing for different types of binding modes, including L,L- and L,X-type bidentate and monodentate binding. Kinetic and computational studies support the proposed mechanisms for perdeuteration and alkenylation, and the findings reveal crucial factors in the design of ligands for Pd-catalyzed C–H functionalization, which will be useful for further development of pyrazole- and pyridone-containing ligands in transition metal catalysis. 

Nondirected Pd-Catalyzed C–H Perdeuteration and meta-Selective Alkenylation of Arenes Enabled by Pyrazolopyridone Ligands

This study was designed to obtain a quantified TUG test index that can be used as data on the risk assessment of the elderly, early diagnosis of Parkinson's disease, and post-stroke rehabilitation. Data is acquired through TUG test using the IMU sensor attached to the bottom of shank and the sEMG sensor attached to the TA muscle. Based on acquired kinematic and electromyography data, we derive walking and cognitive indexes such as reaction speed, tremor, and walking distance. Equipment design and pilot testing for clinical trials were conducted.

Minkyu Kim

Papers

Designing a smart heterojunction coupling of cobalt-iron layered double hydroxide on nickel selenide nanosheets for highly efficient overall water splitting kinetics

Synthesis of Bidentate Nitrogen Ligands by Rh-Catalyzed C-H Annulation and Their Application to Pd-Catalyzed Aerobic C-H Alkenylation.

Divergent Strategies for the π-Extension of Heteroaryl Halides Using Norbornadiene as an Acetylene Synthon.

Nondirected Pd-Catalyzed C–H Perdeuteration and meta-Selective Alkenylation of Arenes Enabled by Pyrazolopyridone Ligands

Quantitative Evaluation of TUG Test with IMU and sEMG Sensors in Wearable Device (Poster)