Xin-Xing Wu

Facile Synthesis of Disubstituted Isoxazoles from Homopropargylic Alcohol via C═N Bond Formation

A novel iron-catalyzed aerobic oxidative reaction to synthesize disubstituted isoxazoles from homopropargylic alcohol, t-BuONO, and H2O is developed. The method provides mild conditions to afford a variety of useful substituted heterocycles in an efficient and regioselective manner. The mechanism has been studied and proposed, which indicates that the transformation can be realized through construction of a C═N bond and C═O bond, C-H oxidation, and then cyclization. Moreover, this method can be enlarged to gram scale.

Synthesis of polycyclic substituted vinylarenes via a one-pot intramolecular aryl alkylation–N-tosylhydrazone insertion reaction

A novel method of a palladium-catalyzed/norbornene-mediated intramolecular C-H activation/N-tosylhydrazones insertion reaction is developed. In this process, various bicyclic or tricyclic substituted vinylarenes are obtained with high efficiency under mild conditions.

Palladium-Catalyzed Radical Cascade Iododifluoromethylation/Cyclization of 1,6-Enynes with Ethyl Difluoroiodoacetate

A novel and convenient Pd-catalyzed radical cascade iododifluoromethylation/cyclization of 1,6-enynes with ethyl difluoroiodoacetate is demonstrated. The proposed transformation presents high stereoselectivity under mild and facile reaction conditions, thereby allowing an efficient access to a variety of iodine-containing difluoromethylated pyrrolidines. A possible radical pathway for the transformation is proposed on the basis of the results of control experiments and relevant literature reviews.

Palladium-Catalyzed Domino Heck/Intermolecular C–H Bond Functionalization: Efficient Synthesis of Alkylated Polyfluoroarene Derivatives

An efficient palladium-catalyzed alkylation of electron-deficient polyfluoroarenes is described. The protocol provides a useful and operationally simple access to a broad scope of alkylated polyfluoroarene derivatives in moderate to excellent yields. This also represents the first example of the introduction of a polyfluoroarene structure involving an alkylpalladium(II) intermediate.

Silver-Catalyzed Oxidative Cyclization of Propargylamide-Substituted Indoles: Synthesis of Phosphorated Indoloazepinones Derivatives

A silver-catalyzed oxidative cyclization of 2- or 3-propargylamide-substituted indoles to synthesize phosphorated indoloazepinone derivatives is described. This reaction displays a difunctionalizalion of alkynes with diphenylphosphine oxides to construct a seven-membered ring through a radical cyclization process. The indoloazepinones derivatives are common structural motifs found in many natural products and pharmaceuticals.

Palladium-Catalyzed Dearomative Cyclization by a Norbornene-Mediated Sequence: A Route to Spiroindolenine Derivatives.

The first palladium-catalyzed dearomative cyclization via a modified Catellani-type C-H functionalization has been realized. The new strategy led to a series of spiroindolenine derivatives bearing an all-carbon quaternary spirocenter from simple aryl halides and substituted indoles.

Lewis Acid Mediated Tandem Reaction of Propargylic Alcohols with Hydroxylamine Hydrochloride To Give α,β-Unsaturated Amides and Alkenyl Nitriles.

We have developed a highly selective method for the synthesis of α,β-unsaturated amides and alkenyl nitriles from readily available propargylic alcohols. The reaction proceeded smoothly under the neutral conditions with hydroxylamine hydrochloride (NH2OH·HCl) as the nitrogen source. The development of these new strategies has significantly extended the application of hydroxylamine hydrochloride to the chemistry of propargylic alcohols. Moreover, both secondary and tertiary alcohols have been highly regioselectively transformed to the desired products with good functional group compatibility.

Palladium-Catalyzed Intramolecular Dearomatization of Indoles via Decarboxylative Alkynyl Termination.

A highly diastereoselective dearomatization of indoles via palladium-catalyzed decarboxylative alkynyl termination was developed. This protocol provides dissimilar tetracyclic and tetrasubstituted indoline scaffolds bearing congested stereocenters, which led to operationally simple conditions, short time, and broad substrate scope. Additionally, this reaction system could be scaled to gram quantities in a satisfactory yield and diastereoselectivity.

A metal-free transformation of alkynes to carbonyls directed by remote OH group

A remote OH group-directed metal-free transformation of alkynes to carbonyl compounds has been developed. Using only HOAc and EtOH solvent, this reaction elegantly converts alkynes into valuable ketones by remote hydroxyl group activation. Through comparison and isotope labeling experiments, it was confirmed that the process operates via a hydration reaction involving an acetic acid molecule, instead of a water molecule.