Guojiao Wu

Copper-Catalyzed Direct Benzylation or Allylation of 1,3-Azoles with N-Tosylhydrazones

Cu-catalyzed cross-coupling of N-tosylhydrazones with 1,3-azoles leads to the direct C-H benzylation or allylation. Cu carbene migratory insertion is proposed to play the key role in this transformation.

Cu(I)-Catalyzed Cross-Coupling of Terminal Alkynes with Trifluoromethyl Ketone N-Tosylhydrazones: Access to 1,1-Difluoro-1,3-enynes

C-C Bond formation and β-F elimination have been achieved in a Cu(I)-catalyzed cross-coupling reaction of terminal alkynes and trifluoromethyl ketone N-tosylhydrazones. The reaction represents an efficient synthesis of 1,1-difluoro-1,3-enyne derivatives. Mechanistically, the migratory insertion of the copper carbene intermediate leads to the C-C bond formation, which is followed by C-F bond cleavage.

Silver(I)‐Catalyzed N‐Trifluoroethylation of Anilines and O‐Trifluoroethylation of Amides with 2,2,2‐Trifluorodiazoethane

A straightforward N-trifluoroethylation of anilines has been developed based on silver-catalyzed N-H insertions with 2,2,2-trifluorodiazoethane (CF3CHN2). Mechanistically, the reaction is proposed to involve migratory insertion of a silver carbene as the key step. In contrast, when amides are employed as the substrates under similar reaction conditions, O-trifluoroethylation occurs to afford trifluoroethyl imidates.

Copper(I)‐Catalyzed Alkylation of Polyfluoroarenes through Direct CH Bond Functionalization

The copper(I)-catalyzed alkylation of electron-deficient polyfluoroarenes with N-tosylhydrazones and diazo compounds has been developed. This reaction uses readily available starting materials and is operationally simple, thus representing a practical method for the construction of C(sp(2) )-C(sp(3) ) bonds with polyfluoroarenes through direct C-H bond functionalization. Mechanistically, copper(I) carbene formation and subsequent migratory insertion are proposed as the key steps in the reaction pathway.

Microwave-Assisted, Pd(0)-Catalyzed Cross-Coupling of Diazirines with Aryl Halides

Pd(0)-catalyzed cross-coupling reactions of diazirines with aryl halides under microwave heating conditions afford a series of substituted olefins. A reaction mechanism involving the migratory insertion of the Pd carbene intermediate is proposed.

Synthesis of α‐Aryl Esters and Nitriles: Deaminative Coupling of α‐Aminoesters and α‐Aminoacetonitriles with Arylboronic Acids

Transition-metal-free synthesis of α-aryl esters and nitriles using arylboronic acids with α-aminoesters and α-aminoacetonitriles, respectively, as the starting materials has been developed. The reaction represents a rare case of converting C(sp(3))-N bonds into C(sp(3))-C(sp(2)) bonds. The reaction conditions are mild, demonstrate good functional-group tolerance, and can be scaled up.

Catalytic asymmetric trifluoromethylthiolation via enantioselective [2,3]-sigmatropic rearrangement of sulfonium ylides

The trifluoromethylthio (SCF3) functional group has been of increasing importance in drug design and development as a consequence of its unique electronic properties and high stability coupled with its high lipophilicity. As a result, methods to introduce this highly electronegative functional group have attracted considerable attention in recent years. Although significant progress has been made in the introduction of SCF3 functionality into a variety of molecules, there remain significant challenges regarding the enantioselective synthesis of SCF3-containing compounds. Here, an asymmetric trifluoromethylthiolation that proceeds through the enantioselective [2,3]-sigmatropic rearrangement of a sulfonium ylide generated from a metal carbene and sulfide (Doyle–Kirmse reaction) has been developed using chiral Rh(II) and Cu(I) catalysts. This transformation features mild reaction conditions and excellent enantioselectivities (up to 98% yield and 98% e.e.), thus providing a unique, highly efficient and enantioselective method for the construction of C(sp3)–SCF3 bonds bearing chiral centres. The asymmetric Doyle–Kirmse reaction using chiral Rh(II)- or Cu(I)-catalysts provides SCF3-containing compounds in a highly efficient and enantioselective manner. The reaction proceeds through enantioselective formation of sulfonium ylide from a diazoester and allyl- or propargyl trifluoromethyl sulfide, followed by concerted [2,3]-sigmatropic rearrangement with the transfer of chirality from sulfur to carbon.

Copper(I)-Catalyzed Chemoselective Coupling of Cyclopropanols with Diazoesters: Ring-Opening C-C Bond Formations

Reported herein is an exceptional chemoselective ring-opening/C(sp3 )-C(sp3 ) bond formation in the copper(I)-catalyzed reaction of cyclopropanols with diazo esters. The conventional O-H insertion product is essentially suppressed by judicious choice of reaction conditions. DFT calculations provide insights into the reaction mechanism and the rationale for this unusual chemoselectivity.

Palladium-Catalyzed Oxygenative Cross-Coupling of Ynamides and Benzyl Bromides by Carbene Migratory Insertion

A palladium-catalyzed oxygenative cross-coupling of ynamides and benzyl bromides has been developed. After subsequent hydrogenation, α,α-disubstituted amide derivatives were obtained in good yields. Migratory insertion of α-oxo palladium carbene species, generated by intermolecular oxidation, is proposed as the key step in this reaction. The study demonstrates the potential of ynamides to serve as carbene precursors in palladium-catalyzed C-C bond-forming cross-coupling reactions.

One-carbon homologation of arylboronic acids: a convenient approach to the synthesis of pinacol benzylboronates

A transition-metal-free method for the synthesis of benzylic boronate esters with arylboronic acids and trimethylsilyldiazomethane (TMSCHN2) has been developed. This transformation is a straightforward homologation of arylboronic acids, which represents a unique approach toward the preparation of pinacol benzylboronates. The reaction has a wide substrate scope and good functional-group tolerance, and it can be scaled up easily.