Qing-Qing Yang

Synthesis of Indoles through Highly Efficient Cascade Reactions of Sulfur Ylides and N‐(ortho‐Chloromethyl)aryl Amides

Batting the ylides: A simple procedure carried out under mild conditions allows the direct and efficient synthesis of structurally diverse indoles. This approach involves a cascade reaction of sulfur ylides and N-(ortho-chloromethyl)aryl amides.

Enantioselective Intramolecular Crossed Rauhut–Currier Reactions through Cooperative Nucleophilic Activation and Hydrogen‐Bonding Catalysis: Scope and Mechanistic Insight

A highly efficient and enantioselective intramolecular crossed Rauhut-Currier (RC) reaction of nitroolefins with tethered enonates has been developed through cooperative nucleophilic activation and a hydrogen-bonding catalytic strategy (≤98% ee and 98% yield). The reaction features simple experimental procedures and is completely chemoselective and atom-economic in character. The potential synthetic applications have been demonstrated by the conversion of the RC reaction products into biologically and pharmaceutically valuable compounds with highly diastereoselectivity. In addition, computational investigations were employed to support the proposed mechanism and to obtain a good understanding of the origin of the stereoselectivity in RC reactions.

Enantioselective Cascade Michael Addition/Cyclization Reactions of 3‐Nitro‐2H‐Chromenes with 3‐Isothiocyanato Oxindoles: Efficient Synthesis of Functionalized Polycyclic Spirooxindoles

An unprecedented Zn(OTf)2-catalyzed asymmetric Michael addition/cyclization cascade of 3-nitro-2H-chromenes with 3-isothiocyanato oxindoles has been disclosed. This transformation provides an efficient access to various synthetically important polycyclic spirooxindoles in a highly stereoselective manner under mild conditions (72–99% yields, up to >95:5 d.r. and >99% ee). The reaction leads to the formation of three consecutive stereocenters, including 1,3-nonadjacent tetrasubstituted carbon stereocenters, in a single operation. A bifunctional activation model of the chiral Zn(OTf)2/bis(oxazoline) complex was proposed based on control experiments, wherein the ZnII moiety serves as a Lewis acid and the N atom of the free NH group acts as a Lewis base by a hydrogen-bonding interaction.

Asymmetric trapping of zwitterionic intermediates by sulphur ylides in a palladium-catalysed decarboxylation-cycloaddition sequence

Through nearly 50 years of development, sulphur ylides have been established as versatile and powerful reagents for the construction of carbocycles and heterocycles. Despite advances, two important and yet elusive bottlenecks continue to inhibit the advancement of this chemistry: a limited number of reagents with polar groups to react with sulphur ylides, and the wide utilization of chiral auxiliaries or substrates to achieve asymmetric cycloaddition processes in the majority of known reports. Herein, we apply an asymmetric palladium catalysis strategy to the chemistry of sulphur ylides to address these two fundamental problems. We thus achieve an unprecedented decarboxylation-cycloaddition sequence of cyclic allylic esters with sulphur ylides through the enantioselective trapping of Pd-stabilized zwitterionic intermediates by the ylides. As a result, a series of biologically and synthetically important 3-vinyl indolines are rapidly assembled with a high reaction efficiency and stereoselectivity.

Enantioselective Conjugate Addition of Oximes to Trisubstituted β-Nitroacrylates: An Organocatalytic Approach to β2,2-Amino Acid Derivatives

A highly enantioselective organocatalytic intermolecular conjugate addition of oximes to β-nitroacrylates has been developed. The highly functionalized adducts obtained are valuable precursors for asymmetric synthesis, as demonstrated by the synthesis of β(2,2)-amino acids and oxazolidin-2-ones.

Construction of Optically Active Indolines by Formal [4+1] Annulation of Sulfur Ylides and N‐(ortho‐Chloromethyl)aryl Amides

Get asymmetric! Asymmetric [4+1] annulation of sulfur ylides and N-(ortho-chloromethyl)aryl amides allowed the formation of the desired cycloadduct with moderate to high yields and enantioselectivities (see scheme). The described strategy, taking advantage of chiral sulfur ylides, represents a direct procedure to access chiral 2-substituted indolines.

Enantioselective Construction of Oxa- and Aza-Angular Triquinanes through Tandem [4 + 1]/[3 + 2] Cycloaddition of Sulfur Ylides and Nitroolefins

A formal [4 + 1]/[3 + 2] cycloaddition sequence of sulfur ylides and alkene-tethered nitroolefins has been developed. The use of (R)-binol-derived chiral sulfide leads to an asymmetric process that allows the construction of oxa- and aza-angular triquinanes in good to excellent diastereo- and enantioselectivities.

Enantio- and Diastereoselective Synthesis of Spiro-epoxyoxindoles

An asymmetric synthesis of epoxyoxindoles from isatins has been developed by employing chiral sulfur ylides generated in situ from camphor-derived sulfonium salts. This reaction allows an efficient access to enantioenriched spiro-epoxyoxindoles under mild reaction conditions, featuring high yields and excellent enantio- and diastereoselectivities.