홍승윤 교수

Guiding nitrenes away from a migration Nitrogen conventionally shares its electrons in three bonds with one or more partners. A singly bonded nitrogen, or nitrene, is exceptionally reactive and can insert itself into normally inert C–H bonds. If the nitrene forms next to a carbonyl center, though, it tends to react with the C–C bond on the other side instead. Hong et al. used theory to guide the design of an iridium catalyst that inhibits this rearrangement, steering the nitrene toward C–H inser

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 desired ca

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

Small carbocycles such as cyclopropanes and cyclobutanes are widely recognized as key structural motifs in drug discovery campaigns. However, their synthesis remains largely dominated by cycloaddition chemistry, wherein the choice of carbon sources defines the accessible ring size and substitutional diversity. Here, we report a distinct strategy for accessing both cyclopropanes and cyclobutanes from alkenes, enabled by a single-component iodomethylthianthrenium reagent. The key to these transfor