Korea Carbon Capture & Sequestration R&D Center

An unprecedented protocol for urea synthesis directly from methanol and amine was accomplished. The reaction is highly atom-economical, producing hydrogen as the sole byproduct. Commercially available ruthenium pincer complexes were used as catalysts. In addition, no additive, such as a base, oxidant, or hydrogen acceptor, was required. Furthermore, unsymmetrical urea derivatives were successfully obtained via a one-pot, two-step reaction.

Oxidation of alcohols is an essential organic reaction, affording versatile carbonyl groups. To provide a sustainable solution for environmentally harmful traditional oxidation methods, the transition-metal catalyzed acceptor-free dehydrogenation of alcohols has attracted much attention. The widely used catalysts for the dehydrogenation reaction are based on precious metals, which are not economical and environmentally benign. We developed an operationally simple, economical, and environmentally benign acceptorless Fe-catalyzed dehydrogenation of various secondary benzylic alcohols to afford the corresponding ketones and H2. A simple in situ mixture of readily available Fe(III) acetylacetonate, 1,10-phenanthroline, and K2CO3 was identified as an active catalyst for this transformation.

Abstract A combined sonication and microwave irradiation procedure provides the most effective functionalization of ethylenediamine (en) and branched primary diamines of 1‐methylethylenediamine (men) and 1,1‐dimethylethylenediamine (den) onto the open metal sites of Mg 2 (dobpdc) ( 1 ). The CO 2 capacities of the advanced adsorbents 1‐en and 1‐men under simulated flue gas conditions are 19 wt % and 17.4 wt %, respectively, which are the highest values reported among amine‐functionalized metal‐organic frameworks (MOFs) to date. Moreover, 1‐den exhibits both a significant working capacity (12.2 wt %) and superb CO 2 uptake (11 wt %) at 3 % CO 2 . Additionally, this framework showcases the superior recyclability; ultrahigh stability after exposure to O 2 , moisture, and SO 2 ; and exceptional CO 2 adsorption capacity under humid conditions, which are unprecedented among MOFs. We also elucidate that the performance of CO 2 adsorption can be controlled by the structure of the diamine ligands grafted such as the number of amine end groups or the presence of side groups, which provides the first systematic and comprehensive demonstration of fine‐tuning of CO 2 uptake capability using different amines.

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.

Transfer hydrogenation of organic formates and cyclic carbonates was achieved for the first time using a readily available ruthenium catalyst. Nontoxic and economical 2-propanol was used, both as a solvent and hydrogen source, without the need of using flammable H2 gas under high pressure. This method provides an indirect strategy to produce methanol from carbon dioxide under mild conditions as well as an operationally simple and environmentally benign way to reduce formates and carbonates.

Abstract Copper‐catalyzed aerobic coupling of thiols and alcohols affords sulfinates and thiosulfonates. These products are assumed to form via sulfinyl radicals which are not commonly found in oxidative coupling reactions of thiols. A reaction mechanism involving sulfinyl radicals is proposed, and mass and electron paramagnetic resonance (EPR) experimental results are provided. magnified image

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

Abstract Diverse cyclic and acyclic carbonates such as ethylene carbonate, propylene carbonate, glycerol carbonate, and dimethyl carbonate were synthesized in moderate to good yields by the direct coupling of the corresponding alcohols with carbon dioxide in the absence of metal catalysts and inorganic bases. The direct carbonation mechanism of alcohols in the presence of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene, 1‐butyl‐3‐methylimidazolium hexafluorophosphate, and dibromomethane was probed by 18 O‐labeling experiments and chiral alcohol experiments.

Abstract For real‐world postcombustion applications in the mitigation of CO 2 emissions using dry sorbents, adsorption and desorption behaviors should be controlled to design and fabricate prospective materials with optimal CO 2 performances. Herein, we prepared diamine‐functionalized Mg 2 (dobpdc) (H 4 dobpdc=4,4′‐dihydroxy‐(1,1′‐biphenyl)‐3,3′‐dicarboxylic acid). ( 1 ‐diamine) with ethylenediamine (en), primary–secondary ( N ‐ethylethylenediamine—een and N ‐isopropylethylenediamine—ipen), primary–tertiary, and secondary–secondary diamines. A slight alteration of the number of alkyl substituents on the diamines and their alkyl chain length dictates the desorption temperature ( T des ) at 100 % CO 2 , desorption characteristics, and Δ T systematically to result in the tuning of the working capacity. The existence of bulky substituents on the diamines improves the framework stability upon exposure to O 2 , SO 2 , and water vapor, relevant to real flue‐gas conditions. Bulky substituents are also responsible for an interesting two‐step behavior observed for the ipen case, as revealed by DFT calculations. Among the diamine‐appended metal–organic frameworks, 1 ‐een, which has the required adsorption and desorption properties, is a promising material for sorbent‐based CO 2 capture processes. Hence, CO 2 performance and framework durability can be tailored by the judicial selection of the diamine structure, which enables property design at will and facilitates the development of desirable CO 2 ‐capture materials.

Abstract A 1,4‐di(2,6‐diisopropylphenyl)‐1,2,3‐triazol‐5‐ylidene ( tz IPr)‐based PEPPSI‐type palladium complex was developed as an excellent precatalyst for the Suzuki–Miyaura cross‐coupling reaction. The complex showed high activity under mild conditions for the cross‐coupling reactions between various types of aryl chlorides and aryl boronic acids regardless of the steric and electronic nature of the substrates.

Two abnormal N-heterocyclic carbene (aNHC) gold(I) complexes, [(aNHC)AuCl], were prepared from C2-protected imidazolium salts. The air-stable complexes chloro(1-isopropyl-3-methyl-2,4-diphenylimidazol-5-ylidene)gold(I) (5) and chloro(1,4-diisopropyl-3-methyl-2-phenylimidazol-5-ylidene)gold(I) (6) were synthesized via transmetalation using (SMe2)AuCl and the corresponding silver salt such as [(aNHC)AgI] or [(aNHC)2Ag][I] and were fully characterized by NMR and mass spectroscopy and by X-ray crystallography. To investigate the structure, bonding, and catalytic activity of the aNHC-based Au complexes in comparison with their traditional NHC analogues, the sterically similar NHC-based Au complexes chloro(1,3-diisopropylimidazol-2-ylidene)gold(I) (7) and chloro(3-isopropyl-1-phenylimidazol-2-ylidene)gold(I) (8) were prepared from 1,3-diisopropylimidazolium iodide (3) and 3-isopropyl-1-phenylimidazolium iodide (4), respectively. X-ray crystallography and density functional theory (DFT) calculations showed that the aNHC complexes have longer Au–Ccarbene bond distances than the NHC complexes. Furthermore, DFT calculations predicted that, despite their longer Au–Ccarbene distances, aNHC complexes have stronger binding energies. It is suggested on the basis of additional theoretical analyses that these counterintuitive trends can be rationalized by considering individual factors that comprise the molecular interaction. The efficient back-donation of electrons and the smaller overlap repulsion in NHC complexes render the Au–Ccarbene distance shorter, whereas the stronger Au–Ccarbene bonding in the aNHC-Au complexes is attributed to the greater electrostatic attraction and the higher electron-donating ability of the carbene lone pair orbital. Catalytic activities of the NHC-based Au complexes were also compared in the alkyne hydration. Traditional NHC-based Au complexes exhibited higher efficiency in the reaction.

Abstract Direct carboxylation of acetylene with CO 2 was carried out in the presence of 1,5,7‐triazabicyclo[4.4.0]dec‐1‐ene (TBD); subsequent reduction of dicarboxylated acetylene produces commercially valuable succinate salts. This metal‐free carboxylation has potential economic and environmental impact by utilizing non‐petroleum feedstocks (acetylene) and CO 2 and by producing valuable chemical feed stocks.

A novel Zr-fumarate (Zr-fum) metal organic framework was synthesized by the reaction of zirconium chloride and fumaric acid under solvothermal conditions without a formic acid modulator. The synthesized material was characterized by the powder X-ray diffraction, Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), and Brunauer-Emmett-Teller (BET) techniques. The results of powder XRD showed the presence of amorphous and crystalline phases. The surface area and average pore diameter of the material were found to be 205.49 m2/g and 2.12 nm, respectively, and TGA showed that the material was stable up to 300°C. The CO2 adsorption properties of the Zr-fum MOF revealed an uptake of 8 wt% at room temperature (25°C) and atmospheric pressure. The cyclic CO2 sorption study showed the complete recyclability of the synthesized material, suggesting that the material has potential for use in gas sorption and separation.

A organocatalytic system based on economical and readily available cyanuric acid has been developed for the synthesis of 2-oxazolidinones and quinazoline-2,4(1H,3H)-diones from propargylamines and 2-aminobenzonitriles under atmospheric pressure carbon dioxide. Notably, a low concentration of carbon dioxide in air was directly converted into 2-oxazolidinone in excellent yields without an external base. Through mechanistic investigation by in situ FTIR spectroscopy, cyanuric acid was demonstrated to be an efficient catalyst for carbon dioxide fixation.

It is a constant challenge to develop an environmentally friendly, atom-economical, and step-economical method for the preparation of thioamides. Herein, we describe an oxidation method that affords the direct conversion of thiols to thioamides without the use of exogenous sulfur reagents. This is the first instance of a successful utilization of thiols as a synthon for the preparation of thioamides under economical conditions.

Despite the remarkable success of the copper-catalyzed oxidative coupling reaction, direct cross-coupling of amines and thiols for the synthesis of N-sulfenylimines has not been previously reported. Using commercially available copper catalysts (CuI) and oxygen as an environmentally benign oxidant, synthetically useful N-sulfenylimines were prepared from amines and thiols in good yields without overoxidation of sulfur atoms.

The role of CH-π and CF-π interactions in determining the structure of N-heterocyclic carbene (NHC) palladium complexes were studied using (1) H NMR spectroscopy, X-ray crystallography, and DFT calculations. The CH-π interactions led to the formation of the cis-anti isomers in 1-aryl-3-isopropylimidazol-2-ylidene-based [(NHC)2 PdX2 ] complexes, while CF-π interactions led to the exclusive formation of the cis-syn isomer of diiodobis(3-isopropyl-1-pentafluorophenylimidazol-2-ylidene) palladium(II).

The Brønsted acid catalyzed Meyer-Schuster reaction of hemiaminals was studied for the stereoselective synthesis of β-enaminones. Hemiaminals were formed from propargyl aldehydes (or the oxidation of propargyl alcohols) and amines in the presence of Brønsted acids. A critical step to control the stereochemistry of the products is the protonation of the corresponding allenol intermediate, which is dictated by the Brønsted acid used, the steric effect of the amine, and the electronic effect of the propargyl aldehyde.

Abstract A versatile carbene‐catalysed oxidation protocol involving N‐heterocyclic carbene catalysts and 2,2,6,6‐tetramethylpiperidine N ‐oxyl (TEMPO) is described for the synthesis of esters, cinnamic acids, and thioesters. A wide range of esters, thioesters, and cinnamic acids were obtained by metal‐free coupling of aldehydes with aliphatic, allylic and aromatic alcohols, benzyl mercaptan, and water. In addition to the oxidative coupling of aldehydes with nucleophiles, dehydrogenation of saturated aldehydes and oxidation of allylic alcohols were found under our oxidative coupling conditions. Unlike other TEMPO‐mediated oxidative esterification reactions, this reaction does not proceed through a TEMPO ester intermediate to form esters and thioesters.

The ruthenium catalyzed selective sp(3) C-O cleavage with amide formation was reported in reactions of 3-alkoxy-1-propanol derivatives and amines. The cleavage only occurs at the C3-O position even with 3-benzyloxy-1-propanol. Based on the experimental results, O-bound and C-bound Ru enolate complexes were proposed as key intermediates for the unique selective sp(3) C-O bond cleavage in 3-alkoxy-1-propanols.