Jie-Sheng Huang

Terminal Ru(V)–imido species are thought to be as reactive to group transfer reactions as their Ru(V)–oxo homologues, but are less studied. With the electron-rich corrole ligand, relatively stable and isolable Ru(V)–arylimido complexes [Ru(^tBu–Cor)(NAr)] (H₃(^tBu–Cor) = 5,15-diphenyl-10-(p-tert-butylphenyl)corrole, Ar = 2,4,6-Me₃C₆H₂ (Mes), 2,6-(ⁱPr)₂C₆H₃ (Dipp), 2,4,6-(ⁱPr)₃C₆H₂ (Tipp), and 3,5-(CF₃)₂C₆H₃ (BTF)) can be prepared from [Ru(^tBu–Cor)]₂ under strongly reducing conditions. This type of Ru(V)–monoarylimido corrole complex with S = ½ was characterized by high-resolution ESI mass spectrometry, X-band EPR, resonance Raman spectroscopy, magnetic susceptibility, and elemental analysis, together with computational studies. Under heating/light irradiation (xenon lamp) conditions, the complexes [Ru(^tBu–Cor)(NAr)] (Ar = Mes, BTF) could undergo aziridination of styrenes and amination of benzylic C(sp³)–H bonds with up to 90% product yields.

Trifluoromethyl‐bearing 5‐membered rings are prevalent in bioactive molecules, but modular approaches to these compounds by functionalization of robust C(sp³)−H bonds in a direct and selective manner are extremely challenging. Herein we report the rhodium‐catalyzed α‐CF₃‐α‐alkyl carbene insertion into C(sp³)−H bonds of a broad range of substrates to access 7 types of CF₃‐bearing saturated 5‐membered carbo‐ and heterocycles. The reaction is particularly effective for benzylic C−H insertion exerting good site‐, diastereo‐ and enantiocontrol, and applicable to the synthesis of chiral CF₃ analogues of bioactive molecules. Ruthenium α‐CF₃‐α‐alkyl carbene complexes underwent stoichiometric reactions to give C−H insertion products, lending evidence for the involvement of metal α‐CF₃‐α‐alkyl carbene species in the catalytic cycle. DFT calculations revealed that the π⋅⋅⋅π attraction and intra‐carbene C−H⋅⋅⋅F hydrogen bond elucidate the origin of selectivity of the benzylic C−H insertion reactions.

Trifluoromethyl‐bearing 5‐membered rings are prevalent in bioactive molecules, but modular approaches to these compounds by functionalization of robust C(sp³)−H bonds in a direct and selective manner are extremely challenging. Herein we report the rhodium‐catalyzed α‐CF₃‐α‐alkyl carbene insertion into C(sp³)−H bonds of a broad range of substrates to access 7 types of CF₃‐bearing saturated 5‐membered carbo‐ and heterocycles. The reaction is particularly effective for benzylic C−H insertion exerting good site‐, diastereo‐ and enantiocontrol, and applicable to the synthesis of chiral CF₃ analogues of bioactive molecules. Ruthenium α‐CF₃‐α‐alkyl carbene complexes underwent stoichiometric reactions to give C−H insertion products, lending evidence for the involvement of metal α‐CF₃‐α‐alkyl carbene species in the catalytic cycle. DFT calculations revealed that the π⋅⋅⋅π attraction and intra‐carbene C−H⋅⋅⋅F hydrogen bond elucidate the origin of selectivity of the benzylic C−H insertion reactions.

Molecular wheels composed of edge‐shared metal‐ligand coordination octahedra usually feature metal ions that are linked by bridging ligands possessing the same type of donor atoms. Herein we describe heterobridged wheels {Ru_n(μ‐SR)_n(μ‐X)_n}(CO)_2n (R=Trip; n=6, X=Cl, Br; n=8, X=I), which were formed in the reactions between Ru₃(CO)₁₂, 2,4,6‐triisopropylbenzenethiol (HSTrip) and HX (X=Cl, Br) or I₂. These hexa‐ and octanuclear heterobridged wheels featuring thiolate/halide mixed bridging ligands have all been characterized by X‐ray crystallography as well as spectroscopic means including NMR, IR and ESI‐MS.

A chiral Fe^II(N4) complex (N4 = (R,R)-N,N′-bis(2-isopropylquinolin-8-yl)-1,2-diphenylethane-1,2-diamine) was developed for the asymmetric conjugate addition of silyl enol ethers, including both acyclic ones and cyclohexenone-derived ones, to α,β-unsaturated 2-acyl imidazoles. This Fe^II complex is an effective chiral Lewis acid and was applied in the synthesis of an array of chiral 1,5-dicarbonyl synthons and cyclohexenone derivatives with high yields and enantioselectivities (up to 99% ee).

Metal‐catalyzed C−N bond formation reactions via acylnitrene transfer have recently attracted much attention, but direct detection of the proposed acylnitrenoid/acylimido M(NCOR) (R=aryl or alkyl) species in these reactions poses a formidable challenge. Herein, we report on Ru(NCOR) intermediates in C−N bond formation catalyzed by [Ru^IV(Por)Cl₂]/N₃COR, a catalytic method applicable to aziridine/oxazoline formation from alkenes, amination of substituted indoles, α‐amino ketone formation from silyl enol ethers, amination of C(sp³)−H bonds, and functionalization of natural products and carbohydrate derivatives (up to 99 % yield). Experimental studies, including HR‐ESI‐MS and EPR measurements, coupled with DFT calculations, lend evidence for the formulation of the Ru(NCOR) acylnitrenoids as a Ru^V‐imido species.

Reliable methods for enantioselective cis‐dihydroxylation of trisubstituted alkenes are scarce. The iron(II) complex cis‐α‐[Fe^II(2‐Me₂‐BQPN)(OTf)₂], which bears a tetradentate N₄ ligand (Me₂‐BQPN=(R,R)‐N,N′‐dimethyl‐N,N′‐bis(2‐methylquinolin‐8‐yl)‐1,2‐diphenylethane‐1,2‐diamine), was prepared and characterized. With this complex as the catalyst, a broad range of trisubstituted electron‐deficient alkenes were efficiently oxidized to chiral cis‐diols in yields of up to 98 % and up to 99.9 % ee when using hydrogen peroxide (H₂O₂) as oxidant under mild conditions. Experimental studies (including ¹⁸O‐labeling, ESI‐MS, NMR, EPR, and UV/Vis analyses) and DFT calculations were performed to gain mechanistic insight, which suggested possible involvement of a chiral cis‐Fe^V(O)₂ reaction intermediate as an active oxidant. This cis‐[Fe^II(chiral N₄ ligand)]²⁺/H₂O₂ method could be a viable green alternative/complement to the existing OsO₄‐based methods for asymmetric alkene dihydroxylation reactions.