Tiow-Gan Ong

Bimetallic Nickel Aluminun Mediated Para-Selective Alkenylation of Pyridine: Direct Observation of η2,η1-Pyridine Ni(0)−Al(III) Intermediates Prior to C−H Bond Activation

We have presented new amino-NHC Ni-Al complex mediated para C-H bond activation for pyridine and quinolin, and isolated for the first time the intermediate structure of a bimetallic eta(2),eta(1)-pyridine nickel aluminum complex prior to its C-H activation, which serves as key evidence for bimetallic catalysis.

Preparation and Characterization of Amino-Linked Heterocyclic Carbene Palladium, Gold, and Silver Complexes and Their Use as Anticancer Agents That Act by Triggering Apoptotic Cell Death

Transition metal complexes bearing amino linked N-heterocyclic carbenes (NHC) were prepared and evaluated for their antiproliferative activities in human cancer cells. The optimum antiproliferative activity, observed for the gold complex 3 in U-87 MG cells, was found to involve S-phase arrest of the cell cycle. The results indicate that 3 induces apoptosis through a p53-bak pathway, a finding that could serve as a new strategy to reduce the resistance of cancer cells to p53-induced apoptosis.

Metal-free arylation of benzene and pyridine promoted by amino-linked nitrogen heterocyclic carbenes

An amino-linked nitrogen heterocyclic carbene (amino-NHC), 1-tBu, has been shown to mediate carbon-carbon coupling through the direct C-H functionalization of benzene and pyridine in the absence of a metal catalyst. Using EPR, the first spectroscopic evidence corroborating the single electron transfer mechanism for the metal-free carbon-carbon coupling manifold, as reported by others, is introduced.

Expanding the Ligand Framework Diversity of Carbodicarbenes and Direct Detection of Boron Activation in the Methylation of Amines with CO2

A simple and convergent synthetic strategy used to increase the diversity of the carbodicarbene ligand framework through incorporation of unsymmetrical pendant groups is reported. Structural analysis and spectroscopic studies of ligands and their Rh complexes are reported. Reactivity studies reveal carbodicarbenes as competent organocatalysts for amine methylation using CO2 as a synthon. A unique BH-activated boron-carbodicarbene complex was isolated as a reaction intermediate, providing mechanistic insight into the CO2 functionalization process.

Tandem Isomerization and C–H Activation: Regioselective Hydroheteroarylation of Allylarenes

The first Ni-promoted prototype reaction based on the tandem C-H activation of heteroarenes with alkene isomerization is demonstrated, leading to the branched hydroheteroarylation products. Simultaneously, the reaction selectivity can be chemically switched to linear adducts through Ni-Al tandem catalysis.

Synthesis and Isolation of an Acyclic Tridentate Bis(pyridine)carbodicarbene and Studies on Its Structural Implications and Reactivities

The simple synthetic development of acyclic pincer bis(pyridine)carbodicarbene is depicted herein. Presented is the first isolated structural pincer carbodicarbene with a C-C-C angle of 143°, larger than the monodentate framework. More importantly, theoretical analysis showed that this carbodicarbene embodies a more allene-like character. Palladium complexes supported by this pincer ligand are active catalysts for Heck-Mizoroki and Suzuki-Miyaura coupling reactions.

The Regioselective Switch for Amino-NHC Mediated C–H Activation of Benzimidazole via Ni–Al Synergistic Catalysis

We have disclosed a new mode of a chemically regioselective switch for C-H bond functionalization of benzimidazole derivatives via a cooperative effect invoked by Ni-Al bimetallic catalysis to create a steric requirement for obtaining the linear product of styrene insertion. Yet, excluding the AlMe(3) cocatalyst switches the reaction toward branch selectivity.

The Elusive Three-Coordinate Dicationic Hydrido Boron Complex

The formation of a hitherto unknown three-coordinate dicationic hydrido boron complex is described. Interestingly, supporting ligand carbodicarbene gave unprecedented reaction with BH3 without using more highly electrophilic Lewis acid precursors. Spectroscopic, crystallographic, and computational analysis was performed to understand the electronic features of these species.

Catalytic C=N bond metathesis of carbodiimides by group 4 and 5 imido complexes supported by guanidinate ligands.

A family of guanidinate-supported imido metal complexes are novel, effective catalysts for C=N metathesis of alkyl and aryl carbodiimides and evidence suggests that this reaction proceeds via a sequential addition/elimination pathway.

Complementary Helicity Interchange of Optically Switchable Supramolecular-Enantiomeric Helicenes with (−)-Gel-Sol-(+)-Gel Transition Ternary Logic

A gallamide-containing pseudoenantiomeric helicene pair bearing a (10R,11R)-dimethoxymethyldibenzosuberane core can self-assemble by intermolecular amide H-bonding and π-π stacking into bundled helical fibers with helical tunnels of complementary helicity in CH2Cl2. The helicenes undergo excellent complementary photoswitchings of ternary logic at 280, 318, and 343 nm through (-)-gel-sol-(+)-gel interconversion.