Chao-Jun Li

Magnetic copper–iron nanoparticles as simple heterogeneous catalysts for the azide–alkyne click reaction in water

The development of a novel bimetallic copper–iron nanoparticle synthesis provides a recoverable heterogeneous catalyst for the azide–alkyne “click” reaction in water. The nanoparticles catalyze the production of a diverse range of triazoles, while separation and reuse proved to be easy.

Aerobic and Electrochemical Oxidative Cross‐Dehydrogenative‐Coupling (CDC) Reaction in an Imidazolium‐Based Ionic Liquid

The ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate [BMIm][BF(4)] has demonstrated high efficiency when applied as a solvent in the oxidative nitro-Mannich carbon--carbon bond formation. The copper-catalyzed cross-dehydrogenative coupling (CDC) between N-phenyltetrahydroisoquinoline and nitromethane in [BMIm][BF(4)] occurred with high yield under the described reaction conditions. Both the ionic liquid and copper catalyst were recycled nine times with almost no lost of activity. The electrochemical behavior of the tertiary amine substrate and beta-nitroamine product was investigated employing [BMIm][BF(4)] as electrolyte solvent. The potentiostatic electrolysis in ionic liquid afforded the desired product with a high yield. This result and the cyclic voltammetric investigation provide a better understanding of the reaction mechanism, which involves radical and iminium cation intermediates.

Iron-catalyzed arylation of benzoazoles with aromatic aldehydes using oxygen as oxidant

An iron-catalyzed arylation of azoles with aromatic aldehydes using oxygen as oxidant has been discovered. The reaction proceeded well for a range of different substrates under oxidative conditions.

“On water”-promoted direct alkynylation of isatins catalyzed by NHC–silver complexes for the efficient synthesis of 3-hydroxy-3-ethynylindolin-2-ones

The direct alkynylation of isatins catalyzed by NHC–Ag complexes via the activation of alkyne C–H bond on water was developed for the efficient synthesis of 3-hydroxy-3-ethynylindolin-2-ones under an air atmosphere. A remarkable rate-enhancement by water in the aqueous heterogeneous system was observed.

Highly efficient iron(0) nanoparticle-catalyzed hydrogenation in water in flow

Highly efficient catalytic hydrogenations are achieved by using amphiphilic polymer-stabilized Fe(0) nanoparticle (Fe NP) catalysts in ethanol or water in a flow reactor. Alkenes, alkynes, aromatic imines and aldehydes were hydrogenated nearly quantitatively in most cases. Aliphatic amines and aldehydes, ketone, ester, arene, nitro, and aryl halide functionalities are not affected, which provides an interesting chemoselectivity. The Fe NPs used in this system are stabilized and protected by an amphiphilic polymer resin, providing a unique system that combines long-term stability and high activity. The NPs were characterized by TEM of microtomed resin, which established that iron remains in the zero-valent form despite exposure to water and oxygen. The amphiphilic resin-supported Fe(0) nanoparticles in water and in flow provide a novel, robust, cheap and environmentally benign catalyst system for chemoselective hydrogenations.

Reversing aggregation: direct synthesis of nanocatalysts from bulk metal. Cellulose nanocrystals as active support to access efficient hydrogenation silver nanocatalysts

A highly atom-economical synthetic method to access nanocatalysts from bulk metal is described. A water suspension of cellulose nanocrystals was exposed to an Ag wire, under air and light exposure. In 2 weeks, Ag nanoparticles of size 1.3 nm ± 0.3 nm were deposited onto the biopolymer. These species were active for the hydrogenation of aldehydes, 4-nitrophenol, alkenes and alkynes.

A concise chemical synthesis of (+)-3-deoxy-D-glycero-D-galacto-nonulosonic acid (KDN)

The sialic acid KDN is synthesized stereoselectively in three steps from D-mannose by taking advantage of an indium mediated coupling reaction in aqueous medium.

Palladium-Catalyzed Tandem Oxidative Arylation/Olefination of Aromatic Tethered Alkenes/Alkynes

We describe herein a palladium-catalyzed tandem oxidative arylation/olefination reaction of aromatic tethered alkenes/alkynes for the synthesis of dihydrobenzofurans and 2u2009H-chromene derivatives. This reaction features a 1,2-difunctionalization of C-C π-bond with two C-H bonds using O2 as terminal oxidant at room temperature. The products obtained are valuable synthons and important scaffolds in biological agents and natural products.