Han Yong Bae

In this study, water was demonstrated to be an exceptionally efficient reaction medium for the noncovalent, hydrogen-bonding-promoted enantioselective Michael addition of malonates to diverse nitroolefins using cinchona-based squaramide catalysts. A significant increase in the reaction rate was observed when the reaction was performed “on water” rather than in the conventional organic solvents, because of the hydrophobic hydration effect. This hydrophobic amplification was significantly dependen

Cinchona-based bifunctional catalysts have been extensively employed in the field of organocatalysis due to the incorporation of both hydrogen-bonding acceptors (quinuclidine) and hydrogen-bonding donors (e.g., alcohol, amide, (thio)urea and squaramide) in the molecule, which can simultaneously activate nucleophiles and electrophiles, respectively. Among them, cinchona-derived (thio)urea and squaramide catalysts have shown remarkable application potential by using their bifurcated hydrogen bondi

Carbon dioxide (CO2) is an intrinsically stable molecule. However, its reactivity toward nucleophilic bases has constituted an appealing characteristic for applications such as CO2 capture and functionalization. To shed light on the role of nucleophilic bases in CO2 functionalization, we performed some mechanistic studies using nitrogen-containing bases as an additive—in catalytic amounts—for carboxylation reactions of Grignard reagents. Our kinetic analysis and in situ infrared spectroscopy rev

The Mukaiyama aldol reaction is a widely applied carbon-carbon bond forming reaction. However, despite numerous well-established methods using aldehydes as acceptors, only few examples exist with ketones. Here we report a highly practical catalytic approach to this transformation, namely, the triflimide catalyzed Mukaiyama aldol reaction of silyl ketene acetals with ketones. This method exhibits a broad substrate scope, is very rapid, tolerates functionalized substrates, and requires only parts-

G-, V-, and A-series nerve agents are extremely toxic organophosphorus chemical warfare agents (CWAs) that incorporate P═O functional groups. Their colorless, tasteless, and odorless nature makes rapid and efficient detection challenging. Here, we report an unprecedented N-triflyl phosphoric triamide (<b>N-TPT</b>) receptor, which is a new class of triple hydrogen bonding donor molecular sensors for CWA recognition via noncovalent host-guest-type interactions. The highly robust trifurcate struct

β-Sulfido sulfonyl fluoride and its derivatives have been gaining attention recently in the fields of medicinal chemistry and material science. The conventional method for the synthesis of functionalized alkyl sulfonyl fluorides requires several chemical transformations. Therefore, a direct establishment of such chemical structures remains challenging, and an efficient catalytic approach is highly desired. Herein a significant "on-water" hydrophobic amplification was achieved, enabling a high-tu

<i>Streptomyces</i> spp. are well-known symbiotic microorganisms that produce antimicrobial metabolites against various pathogens. We isolated actinomycetes from the body surface of the termite <i>Odontotermes formosanus</i> and identified it as <i>Streptomyces neopeptinius</i> BYF101 based on 16S rRNA phylogenetic analysis. Chemical analysis of the cultures of termite-associated <i>S. neopeptinius</i> BYF101 via HR-MS² and GNPS analyses enabled the isolation and identification of 20

Abstract In this study, dithiomalonates (DTMs) were demonstrated to be exceptionally efficient Mannich donors in terms of reactivity and stereoselectivity in cinchona‐based‐squaramide‐catalyzed enantioselective Mannich reactions of diverse imines or α‐amidosulfones as imine surrogates. Owing to the superior reactivity of DTMs as compared to conventional malonates, the catalyst loading could be reduced to 0.1 mol % without the erosion of enantioselectivity (up to 99 % ee ). Furthermore, by the us

Herein, a water-accelerated, N-heterocyclic carbene (NHC)-catalyzed aza-Michael addition reaction was reported to access β-aminosulfonyl fluorides, which are key hubs of the sulfur(VI) fluoride exchange (SuFEx) reaction. As a crucial reaction medium, water considerably enhanced the reaction rate with excellent chemo- and site-selectivity (up to >99 : 1) compared to conventional solvents. In addition, the late-stage ligation of bioactive molecules with the aliphatic β-amino SuFEx hub was demonstr

Sulfur(VI) fluoride exchange (SuFEx) is recognized as another emerging tool for click chemistry. The preparation of the functionalized alkyl sulfonyl fluorides as key SuFEx hubs via C(sp³)-C(sp³) bond formation is exceptionally challenging. We report herein a new efficient method for accessing alkyl sulfonyl fluorides incorporating γ-geminal dithioester via phosphazene catalysis. The aqueous, neutral organosuperbase catalytic system amplifies the reactivity by taking advant

<i>Kaempferia parviflora</i> Wall. ex Baker (Zingiberaceae), commonly known as Thai ginseng or black ginger, is a tropical medicinal plant in many regions. It has been traditionally used to treat various ailments, including ulcers, dysentery, gout, allergies, abscesses, and osteoarthritis. As part of our ongoing phytochemical study aimed at discovering bioactive natural products, we investigated potential bioactive methoxyflavones from <i>K. parviflora</i> rhizomes. Phytochemical analysis aided

Colorimetric papers have been widely used for the convenient and inexpensive detection of toxic chemicals including chemical warfare agents (CWAs). The majority of colorimetric papers, however, only detect liquid-phase analytes, exhibiting a limited gas-sensing performance. In this study, we report a colorimetric paper capable of detecting and identifying CWAs in both liquid and gas phases, achieved by inkjet-printing carbon nanotube (CNT)-based chemiresistors on the paper. The inkjet-printed CN

We report herein solvent-free cyanosilylation of ketones catalyzed by 50 ppm of tritylium tetrakis(pentafluorophenyl)borate ([Ph3C]+[B(C6F5)4]−) as an extremely active organocatalyst.