홍승윤 교수

Intramolecular insertion of metal nitrenes into carbon-hydrogen bonds to form γ-lactam rings has traditionally been hindered by competing isocyanate formation. We report the application of theory and mechanism studies to optimize a class of pentamethylcyclopentadienyl iridium(III) catalysts for suppression of this competing pathway. Modulation of the stereoelectronic properties of the auxiliary bidentate ligands to be more electron-donating was suggested by density functional theory calculations

Catalytic reactions that construct carbon-nitrogen bonds are one of central themes in both synthetic and medicinal chemistry since the obtainable nitrogen-containing motifs are commonly encountered in natural products and have also seen a growing prominence as key structural features in marketed drugs and preclinical candidates. Pd-catalyzed cross-couplings, such as Buchwald-Hartwig amination, are at the forefront of such synthetic methods in practical settings. However, they require prefunction

A change in reaction pathway was achieved for the first time by tuning the cyclopentadienyl (Cp) ligand used for the rhodium-catalyzed cyclization of benzamides with conjugated enynones. Depending on the Cp ligand, the reaction pathway switched between [4+2] and [4+1] annulation. Electronic effects turned out to be crucial for the product distribution. The dichotomy was attributed to the alteration of the Lewis acidity of the resultant Cp-bound rhodium species.

Among the central themes in synthetic chemistry is the establishment of novel strategies that usher in the development of more efficient and mild reactions and also expand the chemical space for asymmetric catalysis. Herein, we present an approach to revitalize the Cp*Ir(κ²-LX) system as a catalyst toward alkene difunctionalizations via a nitrenoid-mediated pathway. A key strategy is tuning the orbital symmetry of the key Ir nitrenoid intermediates by ligand modification to impart the

Abstract A change in reaction pathway was achieved for the first time by tuning the cyclopentadienyl (Cp) ligand used for the rhodium‐catalyzed cyclization of benzamides with conjugated enynones. Depending on the Cp ligand, the reaction pathway switched between [4+2] and [4+1] annulation. Electronic effects turned out to be crucial for the product distribution. The dichotomy was attributed to the alteration of the Lewis acidity of the resultant Cp‐bound rhodium species.

Reported herein is a general platform of a stereodefined access to γ-lactams via Cp*Ir-catalyzed olefin difunctionalization, where in situ generated Ir-nitrenoid is utilized as a key motif of 1,3-dipoles to enable amido transfer in a syn-selective manner. Computational studies suggested that the stereodefined process can be attributed to the proposed working mode of concerted [3 + 2] cyclization. Frontier molecular orbital (FMO) analysis implied that a low-lying lowest unoccupied molecular orbit

A catalytic approach to intercept the transient HNO for a chemoselective primary amination of arylboronic acids is reported. A phosphetane-based catalyst operating within P^III/P^V═O redox cycling is shown to capture HNO, generated in situ by Nef decomposition of 2-nitropropane, to selectively install the primary amino group at aryl C_sp2 centers. The method furnishes versatile primary arylamines from arylboronic acid substrates with the preservation of otherwise re

Described herein is the application of a strategy of ligand participation for the Ir-catalyzed imido transfer into alkynes. On the basis of a stoichiometric [3 + 2] cycloaddition of Cp*Ir(III)(κ²- N, O-chelate) with alkynyl dioxazolone, a catalytic haloamidation was developed for the first time by employing [Cp*IrCl₂]₂ precatalyst and NaX salts (X = Cl or Br) as practical halide sources to furnish synthetically versatile Z-(halovinyl)lactams with excellent stereo

Reported herein is the first example of the Rh(NHC)-catalyzed selective bis C-H alkylation of NNN tridentate chelating compounds in reaction with alkenes. The observed excellent site-selectivity can readily be explained by the postulated rollover pathway in the C-H bond activation step. The reaction is highly facile affording bis-alkylated tridentate products in high yields over a broad range of versatile heteroarene substrates and alkene reactants including ethylene gas, thus enabling its appli

Radical-polar crossover (RPC) is a valuable mechanistic tool for revitalizing traditional radical and polar chemistries by integrating them. However, transitioning from radical to polar pathways across multiple redox events requires precise redox potential matching between the reaction components (catalysts and substrates), which inherently limits the scope of these transformations. Here, we present a cooperative catalytic platform that diverts the key RPC mechanism from outer-sphere to inner-sp

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.