홍순혁 교수

1,4-Benzoquinones have been found to prevent olefin isomerization of a number of allylic ethers and long-chain aliphatic alkenes during ruthenium-catalyzed olefin metathesis reactions. Electron-deficient benzoquinones are the most effective additives for the prevention of olefin migration. This mild, inexpensive, and effective method to block olefin isomerization increases the synthetic utility of olefin metathesis via improvement of overall product yield and purity.

The decomposition of a series of ruthenium metathesis catalysts has been examined using methylidene species as model complexes. All of the phosphine-containing methylidene complexes decomposed to generate methylphosphonium salts, and their decomposition routes followed first-order kinetics. The formation of these salts in high conversion, coupled with the observed kinetic behavior for this reaction, suggests that the major decomposition pathway involves nucleophilic attack of a dissociated phosp

Dinuclear ruthenium complex, with a bridging carbide and a hydride ligand, and methyltricyclohexylphosphonium chloride result from thermal decomposition of olefin metathesis catalyst, (IMesH2)(PCy3)(Cl)2Ru=CH2. Involvement of dissociated phosphine in the decomposition is proposed. The dinuclear complex has catalytic olefin isomerization activity, which can be responsible for competing isomerization processes in certain olefin metathesis reactions.

A novel water-soluble ruthenium olefin metathesis catalyst supported by a poly(ethylene glycol) conjugated saturated 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene ligand is reported. The catalyst displays improved activity in ring-opening metathesis polymerization, ring-closing metathesis, and cross-metathesis reactions in aqueous media.

Transition metal catalyzed oxidative amide synthesis directly from primary alcohols and amines is a highly atom economical transformation that evolves hydrogen gas as the only by-product. Several Ru-, Rh-based homogeneous and Ag-based heterogeneous catalysts have been developed for direct amide synthesis. Most of the developed catalysts showed excellent activity with sterically unhindered alcohols and amines; however, limited activity was observed with sterically hindered alcohols or amines, les

Having a breakdown: Decomposition of the olefin metathesis catalyst [(biph)(PCy3)Cl2RuC(H)Ph] (biph= N,N′-diphenylbenzimidazol-2-ylidene, Cy=cyclohexyl) results in benzylidene insertion into an ortho CH bond of an N-phenyl group of the biph ligand. The ruthenium center further inserts into another ortho CH bond of the other N-phenyl ring to give a new RuC bond as a part of a five-membered metallacycle (see scheme).

Abstract An efficient, operatively simple, acceptorless, and base‐free dehydrogenation of secondary alcohols and nitrogen‐containing heterocyclic compounds was achieved by using readily available ruthenium hydride complexes as precatalysts. The complex RuH 2 (CO)(PPh 3 ) 3 ( 1 ) and Shvo’s complex ( 2 ) showed excellent activities for the dehydrogenation of secondary alcohols and nitrogen containing heterocycles. In addition to complexes 1 and 2 , the complex RuH 2 (PPh 3 ) 4 ( 3 ) also showed m

A carbon capture and use (CCU) strategy was applied to organic synthesis. Carbon dioxide (CO2) captured directly from exhaust gas was used for organic transformations as efficiently as hyper-pure CO2 gas from a commercial source, even for highly air- and moisture-sensitive reactions. The CO2 capturing aqueous ethanolamine solution could be recycled continuously without any diminished reaction efficiency.

The utilizations of omnipresent, thermodynamically stable amides and aliphatic C(sp³ )-H bonds for various functionalizations are ongoing challenges in catalysis. In particular, the direct coupling between the two functional groups has not been realized. Here, we report the synergistic activation of the two challenging bonds, the amide C-N and unactivated aliphatic C(sp³ )-H, via metallaphotoredox catalysis to directly acylate aliphatic C-H bonds utilizing amides as stable

A mild and operationally simple C(sp³ )-H trifluoromethylation method was developed for unactivated alkanes by utilizing a bench-stable Cu^III complex, bpyCu(CF₃ )₃ , as the initiator of the visible-light photoinduced reaction, the source of a trifluoromethyl radical as a hydrogen atom transfer reagent, and the source of a trifluoromethyl anion for functionalization. The reaction was initiated by the generation of reactive electrophilic carbon-centered

The N-monomethyl functionality is a common motif in a variety of synthetic and natural compounds. However, facile access to such compounds remains a fundamental challenge in organic synthesis owing to selectivity issues caused by overmethylation. To address this issue, we have developed a method for the selective, catalytic monomethylation of various structurally and functionally diverse amines, including typically problematic primary aliphatic amines, using methanol as the methylating agent, wh

Abstract A catalyst for the direct synthesis of amides from amines and alcohols, generated in situ from the economically attractive and readily available RuCl 3 , an N‐heterocyclic carbene (NHC), and pyridine, was developed. Of the screened NHC precursors, a less bulky one gave better yields for modestly sterically hindered substrates. In a search for the true catalytic intermediates, Grubbs catalysts were found to be active for the amidation of alcohols under basic conditions, suggesting that a

Methanol was utilized for C1 functionalization of primary amines; N-formylation, N-methylation, and N,N-formylmethylation. The reactions were achieved via dehydrogenation of methanol with a ruthenium-based catalyst. Various amines were selectively functionalized in moderate to excellent yields (30% to 99%). Mechanistic studies revealed that control of the reversibility between dehydrogenation of the hemiaminal to formamide and hydrogenation of the formamide back to the hemiaminal promotes the se

Abstract An N ‐formylation method using methanol as the C 1 source without a stoichiometric amount of activating reagent is described. Nitriles as well as amines can be directly used as substrates. The reaction is catalyzed by an N‐heterocyclic carbene coordinated ruthenium(II) dihydride complex, which mediates methanol dehydrogenation, nitrile reduction, and CN bond formation without any external base, hydrogen acceptor, or oxidant. magnified image

Simple aqueous extraction removed ruthenium byproducts efficiently from ring-closing metathesis (RCM) reactions catalyzed by a poly(ethylene glycol) (PEG) supported N-heterocyclic carbene-based ruthenium complex.