Published papers

We report here on the syntheses of rhodium(I) complexes bearing a phosphine-quinolinolate ligand and the isolation of two classes of important intermediates in the anti-Markovnikov hydroamination of terminal alkynes with secondary amines: vinylidene-bridged dirhodium complexes and (amino)carbene complexes. We first prepared various rhodium(I) complexes bearing a phosphine-quinolinolate ligand and found that some of these complexes had catalytic activity for the anti-Markovnikov hydroamination of terminal alkynes with secondary amines. The reaction of stoichiometric amounts of a (PNO)Rh complex with terminal alkynes provided vinylidene-bridged dirhodium complexes. When the resulting vinylidene complexes were reacted with secondary amines, (amino)carbene complexes were generated, which gave the hydroamination product upon heating with an additive. These results suggest that this anti-Markovnikov hydroamination catalyzed by (PNO)Rh complexes proceeds via vinylidene and (amino)carbene complexes.

Catalytic, regioselective C- H functionalizations have been extensively studied over the past two decades. In this account, we report our results on catalytic C- C, C- Si, and C- halogen bond formation reactions by substitution via the cleavage of C- H bonds. Catalytic arylation with arylboronates was developed and applied to the convenient synthesis of polycyclic aromatic hydrocarbons. Alkenylation reactions were also realized by the use of alkenylboronates and alkenyl esters. Various carbonyl- containing substituents were introduced using carbamoyl chlorides, alkyl chloroformates, acyl chlorides, and cyclic alkenyl carbonates. C- Si bonds were formed by reactions with hydrosilanes and vinylsilanes. C- H halogenation reactions were achieved by a combination of C- H bond cleavage and electrochemical oxidation and were applied to one- pot arylation reactions using the Suzuki- Miyaura coupling prodecure.

Palladium-catalyzed regioselective homocoupling of arylpyridines under anodic oxidation conditions was achieved in the presence of I2. The dimerization of meta-substituted arylpyridines proceeded selectively at less-sterically congested ortho-positions, and the selectivity is different from that reported for the palladium-catalyzed dimerization using Oxone as an oxidant. The dimerization also proceeds using catalytic amounts of both Pd(OAc)2 and I2 under the electrochemical reaction conditions.

The catalytic construction of carbon-carbon bonds in small organic molecules via chain walking is described. Catalytic cycloisomerization of 1,n-dienes via chain walking was achieved using a palladium-1,10-phenanthroline catalyst to form five-membered-ring products. By means of a cycloisomerization/ hydrogenation protocol, 1,7- to 1,14-dienes were selectively converted to bicyclo[4.3.0]nonane derivatives. The use of chain walking provides a new method in organic synthesis to functionalize unreactive carbon-hydrogen bonds by letting the catalyst look for preferable bond-forming sites by moving around on the substrate. © 2012 American Chemical Society.

A convenient method for the synthesis of tetraalkylanthracenes and -pentacenes by means of ruthenium-catalyzed regioselective C-H alkylation of the corresponding acenequinones was developed. Dialkyldiarylpentacene was also synthesized using chemoselective tandem C-H alkylation/C-O arylation of dimethoxypentacenequinone. It was suggested that a tetraalkylpentacene is stable under air in the dark and possesses an appropriate HOMO level as active material for p-type organic field-effect transistors (OFETs). © 2012 American Chemical Society.

The ruthenium-catalyzed hydroarylation of alkynes with benzamides proceeds regio- and stereoselectively through a directed C-H bond cleavage. Preliminary mechanistic investigations indicate that the reaction involves amide-directed ortho-metalation, carbometalation of alkyne, and protonolysis. Similarly, phenylazoles also add to alkynes regioselectively. © 2012 American Chemical Society.