Wing-Yiu Yu

Topical Delivery of Silver Nanoparticles Promotes Wound Healing

Wound healing is a complex process and has been the subject of intense research for a long time. The recent emergence of nanotechnology has provided a new therapeutic modality in silver nanoparticles for use in burn wounds. Nonetheless, the beneficial effects of silver nanoparticles on wound healing remain unknown. We investigated the wound‐healing properties of silver nanoparticles in an animal model and found that rapid healing and improved cosmetic appearance occur in a dose‐dependent manner. Furthermore, through quantitative PCR, immunohistochemistry, and proteomic studies, we showed that silver nanoparticles exert positive effects through their antimicrobial properties, reduction in wound inflammation, and modulation of fibrogenic cytokines. These results have given insight into the actions of silver and have provided a novel therapeutic direction for wound treatment in clinical practice.

Rh-catalyzed intermolecular carbenoid functionalization of aromatic C-H bonds by α-diazomalonates.

A Rh-catalyzed intermolecular coupling of diazomalonates with arene C-H bonds is reported. The reaction is initiated by electrophilic C-H activation, which is followed by coupling of the arylrhodium(III) complex with the diazomalonate. In most cases, arenes with oximes, carboxylic acids, and amines as directing groups cross-couple with diazomalonates with excellent regioselectivities and functional group tolerance, and thus, this reaction offers a new route to α-aryl carbonyl compounds for specific applications.

Pd-Catalyzed Intermolecular ortho-C−H Amidation of Anilides by N-Nosyloxycarbamate

A palladium-catalyzed ortho-C-H amidation of anilides by N-nosyloxycarbamates was developed for the synthesis of 2-aminoanilines. This reaction can be carried out under relatively mild conditions and exhibits excellent regioselectivity and functional group tolerance. The amidation reaction is probably initiated by rate-limiting C-H cyclopalladation (k(H)/k(D) = 3.7) to form an arylpalladium complex, followed by nitrene functionalization.

Rhodium(III)-Catalyzed Intermolecular Direct Amination of Aromatic C–H Bonds with N-Chloroamines

A Rh(III)-catalyzed direct aromatic C-H amination is achieved using N-chloroamines as a reagent. Furthermore, we also developed a one-pot amination protocol involving in situ chlorination of the secondary amines. The catalytic amination operates at mild conditions with excellent functional group tolerance and regioselectivity.

Pd-Catalyzed Ortho-C−H Acylation/Cross Coupling of Aryl Ketone O-Methyl Oximes with Aldehydes Using tert-Butyl Hydroperoxide as Oxidant

A Pd-catalyzed protocol for direct C-H bond acylation by cross coupling of aryl ketone oximes and aldehydes using tert-butyl hydroperoxide (TBHP) as oxidant was developed. With oximes as a directing group for the C-H activation, the coupling with aldehydes was achieved with remarkable regioselectivity. The acylation reactions exhibit excellent functional group tolerance, and both aliphatic and heteroaromatic aldehydes can be effectively coupled to the oximes.

Palladium-Catalyzed Decarboxylative Arylation of C−H Bonds by Aryl Acylperoxides

A Pd(OAc)(2)-catalyzed protocol for decarboxylative arylation of aromatic C-H bond was developed using aryl acylperoxides as inexpensive aryl sources. Substrates containing pyridyl, oxime, and oxazoline groups undergo effectively ortho-selective C-H arylation with excellent functional group tolerance. This arylation should begin by directing-group-assisted cyclopalladation, followed by the reaction of the palladacycle with aryl radicals generated in situ by thermal decomposition of the peroxides.

Palladium-Catalyzed Oxidative Ethoxycarbonylation of Aromatic C−H Bond with Diethyl Azodicarboxylate

This communication describes the Pd(OAc)2-catalyzed ethoxycarbonylation reactions of aromatic C−H bonds using diethyl azodicarboxylate (DEAD) together with Oxone or K2S2O8. Substrates such as 2-arylpyridines, pyrrolidinone, acetylindoline, quinoline, and oximes were ethoxycarbonylated with excellent chemo- and regioselectivities. The catalytic reaction is probably initiated by chelation-assisted cyclopalladation of the ortho-C−H bond. Preliminary studies suggested that reactive ethoxyacyl radicals generated from thermal decomposition of DEAD were involved in the ester formation.

Ruthenium Catalyzed Directing Group-Free C2-Selective Carbenoid Functionalization of Indoles by α-Aryldiazoesters

A directing group-free approach for C2-selective carbenoid functionalization of NH-indoles is presented. Using [RuCl(2)(p-cymene)](2) as catalyst and alpha-aryldiazoesters as carbenoid source, 2-alkylated indoles were obtained in up to 96% isolated yield. Similarly, a regioselective carbenoid functionalization of NH-pyrroles was also achieved.

Palladium-Catalyzed Cross Coupling Reaction of Benzyl Bromides with Diazoesters for Stereoselective Synthesis of (E)-α,β-Diarylacrylates

A Pd-catalyzed cross-coupling reaction of benzyl bromides with alpha-aryldiazoesters is described, and E-alpha,beta-diarylacrylates were obtained in good yields and excellent E-to-Z selectivity (>20:1).

[Cp*RhCl2]2-catalyzed ortho-C–H bond amination of acetophenone o-methyloximes with primary N-chloroalkylamines: convenient synthesis of N-alkyl-2-acylanilines

Rh(III)-catalyzed aromatic C-H amination of acetophenone o-methyloximes with primary N-chloroalkylamines was developed, and the arylamine products were obtained in up to 92% yield. The reaction probably involves rate-limiting electrophilic C-H bond cleavage (kH/kD = 2).