Jianwei Han

Palladium-Catalyzed Double-Suzuki–Miyaura Reactions Using Cyclic Dibenziodoniums: Synthesis of o-Tetraaryls

Palladium-catalyzed double-Suzuki-Miyaura couplings between cyclic dibenziodoniums and arylboronic acids have been developed. As such, a wide range of o-tetraaryls were synthesized in good to excellent yields of 22-94%. Furthermore, tetraphenylene was prepared in 21% isolated yield with 2,2-biphenyldiboronic acid by using this method.

Design of Highly Stable Iminophosphoranes as Recyclable Organocatalysts: Application to Asymmetric Chlorinations of Oxindoles

A new family of tartaric acid derived chiral iminophosphoranes has been developed as highly effective organocatalysts in the asymmetric chlorinations of 3-substituted oxindoles with a high level of enantioselectivity. Importantly, these catalysts are air- and moisture-stable. Recovery of the catalyst after simple chromatographic separation for reuse in the model reaction was achieved; the catalyst can be recycled six times without loss of any enantioselectivity. Several advantages of this catalytic process are high conversion after a very short reaction time at ambient temperature, low catalytic loading, and scale-up to multigram quantities with an excellent enantiomeric excess value of >99%, which meets the enantiomeric purity required for pharmaceutical purposes.

Direct C-arylation of polyfluoroarenes with diaryliodonium salts via Pd(OAc)2-catalysis

A novel approach towards the Pd-catalyzed arylation of electron-deficient polyfluoroarenes with diaryliodonium salts was developed. The desired fluorinated biaryls were synthesized in good yields. The mechanistic insights involving the Pd-II/IV catalytic

Iodine-promoted imino-Diels-Alder reaction of fluorinated imine with enol ether: synthesis of 2-perfluorophenyl tetrahydroquinoline derivatives

Iodine was used to catalyze the hetero-Diels-Aider reaction of pentafluorobenzylidineaniline (C6F5CH=NAr 1) with enol ethers to afford the corresponding tetrahydroquinolines derivatives as a mixture of cis/trans stereoisomers in moderate yields. These products could also be prepared by onepot, three-component reaction of pentafluorophenylaldehyde, anilines, and enol ethers under the same reaction condition. Mild and neutral reaction conditions, facile experimental procedure, and low price of iodine should make this method attractive for practical synthesis of many fluorinated tetrahydroquinoline derivatives

Diaryliodonium salts as efficient Lewis acid catalysts for direct three component Mannich reactions

Diaryliodonium(III) salts, as highly active and versatile Lewis acid catalysts for the direct three component Mannich reaction under solvent free conditions, have been investigated. The Mannich products were isolated in good to excellent yields in a very clean manner. Additionally, the catalyst could be recycled without significant loss of its catalytic activity.

Synthesis and Chiroptical Properties of Double-Helical (M)- and (P)-o-Oligophenylenes

All of the M and P isomers of optically pure oligophenylenes with 6, 8, 10, and 12 phenyl rings were synthesized and fully characterized. The Suzuki cross-coupling reaction has been revealed to be a viable strategy in the syntheses of tetraphenylene derivatives, which, together with the copper-mediated oxidative cross-coupling reaction, were employed in the quest for the oligophenylenes. X-ray diffraction analysis in combination with specific rotation and circular dichroism spectroscopy unambiguously identified the unique covalent double-helical frameworks of these oligophenylene molecules.

Palladium Catalyzed C–I and Vicinal C–H Dual Activation of Diaryliodonium Salts for Diarylation: Synthesis of 4,5-Benzocoumarins

With a strategy that makes use of palladium activation of both C-I and vicinal C-H bonds of diaryliodonium salts, an unprecedented approach in diarylation of coumarins was reported. As such, a wide range of 4,5-benzocoumarins with potential fluorescence properties have been synthesized in good yields. A series of experiments suggested that the formation of two carbon-carbon bonds proceeded in a synergetic manner.

Base promoted direct C4-arylation of 4-substituted-pyrazolin-5-ones with diaryliodonium salts

A metal-free approach for the C4-arylation of 4-substituted-pyrazolin-5-ones with diaryliodonium salts was developed. The reaction proceeded smoothly at room temperature in the presence of DMAP (4-dimethylaminopyridine). As a result, a wide range of desired multi-substituted pyrazolin-5-one derivatives were obtained in good to excellent yields (20–98%).

Our Expedition in Eight‐Membered Ring Compounds: From Planar Dehydrocyclooctenes to Tub‐Shaped Chiral Tetraphenylenes

Our research focus for almost forty years concerning eight-membered ring compounds is herein summarized. The design and preparation of these structurally unique compounds featuring a central cyclooctene ring are described in the context of their planar or tub-shaped conformations. Furthermore, their intrinsic properties and potential applications are also presented.

Tartrate-derived iminophosphorane catalyzed asymmetric hydroxymethylation of 3-substituted oxindoles with paraformaldehyde

The enantioselective synthesis of 3-hydroxymethyl-2-oxindoles was achieved through organocatalysis by a tartrate-derived chiral iminophosphorane in 81–98% yields and up to 94% ee under mild conditions. Of note is that readily available and easily usable paraformaldehyde was employed as a hydroxymethylation C1 unit in the reaction.