Woo-Jin Yoo

Effective Formylation of Amines with Carbon Dioxide and Diphenylsilane Catalyzed by Chelating bis(tzNHC) Rhodium Complexes

The reductive formylation of amines using CO2 and hydrosilanes is an attractive method for incorporating CO2 into valuable organic compounds. However, previous systems required either high catalyst loadings or high temperatures to achieve high efficiency, and the substrate scope was mostly limited to simple amines. To address these problems, a series of alkyl bridged chelating bis(NHC) rhodium complexes (NHC=N-heterocyclic carbene) have been synthesized and applied to the reductive formylation of amines using CO2 and Ph2SiH2. A rhodium-based bis(tzNHC) complex (tz=1,2,3-triazol-5-ylidene) was identified to be highly effective at a low catalyst loading and ambient temperature, and a wide substrate scope, including amines with reducible functional groups, were compatible.

Polymer-Incarcerated Gold−Palladium Nanoclusters with Boron on Carbon: A Mild and Efficient Catalyst for the Sequential Aerobic Oxidation−Michael Addition of 1,3-Dicarbonyl Compounds to Allylic Alcohols

We have developed a polymer-incarcerated bimetallic Au-Pd nanocluster and boron as a catalyst for the sequential oxidation-addition reaction of 1,3-dicarbonyl compounds with allylic alcohols. The desired tandem reaction products were obtained in good to excellent yields under mild conditions with broad substrate scope. In the course of our studies, we discovered that the excess reducing agent, sodium borohydride, reacts with the polymer backbone to generate an immobilized tetravalent boron catalyst for the Michael reaction. In addition, we found bimetallic Au-Pd nanoclusters to be particularly effective for the aerobic oxidation of allylic alcohols under base- and water-free conditions. The ability to conduct the reaction under relatively neutral and anhydrous conditions proved to be key in maintaining good catalyst activity during recovery and reuse of the catalyst. Structural characterization (STEM, EDS, SEM, and N(2) absorption/desorption isotherm) of the newly prepared PI/CB-Au/Pd/B was performed and compared to PI/CB-Au/Pd. We found that while boron was important for the Michael addition reaction, it was found to alter the structural profile of the polymer-carbon black composite material to negatively affect the allylic oxidation reaction.

Sulfuryl chloride as an efficient initiator for the metal-free aerobic cross-dehydrogenative coupling reaction of tertiary amines.

A metal-free cross-dehydrogenative (CDC) reaction of tertiary amines was developed using a catalytic amount of sulfuryl chloride (SO2Cl2) under mild aerobic conditions. On the basis of the nature of SO2Cl2, it was assumed that the reagent acts as a radical initiator to induce the metal-free CDC reaction via a radical-initiated autoxidation mechanism.

Base-mediated carboxylation of unprotected indole derivatives with carbon dioxide.

A simple and straightforward method for the preparation of indole-3-carboxylic acids was discovered through the direct carboxylation of indoles with atmospheric pressure of carbon dioxide (CO(2)) under basic conditions. The key for the reaction was found to be the use of a large excess of LiO(t)Bu as a base to suppress the undesired decarboxylation side reaction.

Visible-Light-Mediated Chan–Lam Coupling Reactions of Aryl Boronic Acids and Aniline Derivatives†

The copper(II)-catalyzed aerobic oxidative coupling reaction between aryl boronic acids and aniline derivatives was found to be improved significantly under visible-light-mediated photoredox catalysis. The substrate scope of this oxidative Chan-Lam reaction was thus expanded to include electron-deficient aryl boronic acids as viable starting materials.

Synthesis of Isocoumarins through Three-Component Couplings of Arynes, Terminal Alkynes, and Carbon Dioxide Catalyzed by an NHC–Copper Complex†

A copper-catalyzed multicomponent coupling reaction between in situ generated ortho-arynes, terminal alkynes, and carbon dioxide was developed to access isocoumarins in moderate to good yields. The key to this CO2-incorporating reaction was the use of a versatile N-heterocyclic carbene/copper complex that was able to catalyze multiple transformations within the three-component reaction.

Efficient visible light-mediated cross-dehydrogenative coupling reactions of tertiary amines catalyzed by a polymer-immobilized iridium-based photocatalyst

The immobilization of an iridium-based heterogeneous photocatalyst via a radical polymerization process is described, and its catalytic activity was evaluated for the aerobic phosphonylation reaction of N-aryl tetrahydroisoquinolines under visible light irradiation.

Visible Light-Mediated Ullmann-Type C–N Coupling Reactions of Carbazole Derivatives and Aryl Iodides

The combined use of an iridium-based photocatalyst and a copper salt under blue light emitting diode irradiation enables the Ullmann-type C-N cross-coupling reaction between carbazole derivatives and aryl iodides to proceed under mild conditions.

Hydrophosphinylation of unactivated alkenes with secondary phosphine oxides under visible-light photocatalysis

A visible light induced hydrophosphinylation of unactivated alkenes with diaryl phosphine oxides was found to occur with good yields and under mild reaction conditions in the presence of an inexpensive and commercially available organic dye as a photocatalyst.

Aerobic Oxidation of a Tertiary Aliphatic Amine Under Visible‐Light Photocatalysis: Facile Synthesis of Methylene‐Bridged Bis‐1,3‐dicarbonyl Compounds

Lights, camera, action! An efficient protocol for the formation of methylene-bridged bis-1,3-dicarbonyl compounds has been developed through an aerobic photocatalytic oxidative coupling reaction between 1,3-dicarbonyl compounds and a tertiary aliphatic amine.