Zhaoqing Xu

Highly Enantioselective Organocatalyzed Vinylogous Michael-Type Reaction for the Construction of Trifluoromethylated All-Carbon Quaternary Stereocenters

The first example of a highly enantioselective vinylogous Michael-type reaction of β,β-disubstituted nitroalkenes is disclosed. A series of biologically important chiral oxindoles, featuring a trifluoromethylated all-carbon quaternary chiral center, were obtained in good yields with excellent enantioselectivities (up to >99% ee).

Copper-catalyzed oxyazidation of unactivated alkenes: a facile synthesis of isoxazolines featuring an azido substituent.

A novel and efficient Cu(OAc)2-catalyzed oxyazidation of unactivated alkenes was developed. The reactions are easy to conduct, occur under mild conditions, and form azido-substituted isoxazolines in good yields.

Highly Regio- and Stereoselective Synthesis of (Z)-Trisubstituted Alkenes via Propyne Bromoboration and Tandem Pd-Catalyzed Cross-Coupling

Contrary to all previous reports, bromoboration of propyne with BBr(3) proceeds in >or=98% syn-selectivity to produce (Z)-2-bromo-1-propenyldibromoborane (1). Although 1 is readily prone to stereoisomerization, it can be converted to the pinacolboronate (2) of >or=98% isomeric purity by treatment with pinacol, which may then be subjected to Negishi coupling to give trisubstituted (Z)-alkenylpinacolboronates (3) containing various R groups in 73-90% yields. Iodinolysis of 3 affords alkenyl iodides (4) in 80-90% yields. All alkenes isolated and identified are >or=98% Z.

Copper-catalyzed intramolecular oxytrifluoromethylthiolation of unactivated alkenes.

A mild, versatile, and convenient method for efficient intramolecular oxytrifluoromethylthiolation of unactivated alkenes catalyzed by Cu(OAc)2 has been developed. The reactions were carried out under aerobic conditions and formed a variety of isoxazolines bearing a -SCF3 substituent.

C–H Bonds Phosphorylation of Ketene Dithioacetals

C-H bond phosphorylation of ketene dithioacetals was achieved under transition-metal-free or AgNO3 mediated conditions. Synthetic transformations of the coupling product provided promising methods for the construction of highly functionalized phosphorylated N-heterocycles and tetrasubstituted alkenes.

Transition-Metal-Free Dehydrosilylative Difluoroamidation of Tetrahydroisoquinolines under Mild Conditions

Disclosed herein is a dehydrosilylative difluoroamidation of α-Csp(3)-H of tetrahydroisoquinolines with α,α-difluoro-α-TMS-acetamides. The process, which occurs at ambient temperature in the absence of any transition metals, provides direct access to a broad range of α,α-difluoroacetamide-substituted tertiary amine derivatives in high yields. Moreover, the method was successfully applied in the Csp(3)-H-directed difluorophosphorylation and difluorocarboxylation under the same conditions.

Efficient and stereoselective synthesis of yellow scale pheromone via alkyne haloboration, Zr-catalyzed asymmetric carboalumination of alkenes (ZACA reaction), and Pd-catalyzed tandem Negishi coupling.

A Pd-catalyzed reaction of allylzincs with the 1-octyne bromoboration product gives the desired allyl-alkenyl coupling products in good yields except with H 2CCHCH 2ZnBr. This reaction is suitable for converting an alkyne bromoboration product 3 into 4 with no isomerization or beta-elimination. The Pd-catalyzed isoalkyl-alkenyl coupling of 4 with the isoalkylzinc reagent derived from 2 provides yellow scale pheromone ( 1) of >/=98% isomeric purity in 34% in six steps from TBDPS-protected homoallyl alcohol.

CuSO4-Mediated Decarboxylative Difluoroacetamidation of α,β-Unsaturated Carboxylic Acids

The first example of decarboxylative difluoroacetamidation of α,β-unsaturated carboxylic acids by using difluoromethyl-substituted carbonyl compounds was disclosed. The procedure, which was mediated by low-cost and benign CuSO4, furnished a broad range of difluorinated alkenes in remarkable yields with only the E configuration in most of the cases. Moreover, the product could be smoothly transformed to the corresponding difluorofunctionalized ester and alcohol in high yields.

Silver-Catalyzed Difluoroamidation of Activated Alkenes for the Construction of Difluorinated 3,3-Disubstituted Oxindoles

A AgOAc catalyzed difunctionalization of activated alkenes through a difluoroamidic radical addition to afford difluoroamidated 3,3-disubstituted oxindoles has been developed. Various functional groups were well tolerated. Moreover, the product could be efficiently derived to the corresponding difluorofunctionalized alcohol, ketone, and ester in high yields. The mechanistic studies revealed that a radical pathway was involved in the transformation.

Development and Application of O-(Trimethylsilyl)aryl Fluorosulfates for the Synthesis of Arynes

A class of o-(trimethylsilyl)aryl fluorosulfates was synthesized by a concise method and successfully used as aryne precursors for the first time. Different trapping agents such as azides, furans, and acyl acetoacetates could successfully react with the aryne precursors under mild conditions with good to excellent yields.