Nickel/Copper-Cocatalyzed Asymmetric Benzylation of Aldimine Esters for the Enantioselective Synthesis of α-Quaternary Amino Acids.

The first asymmetric Ni/Cu cocatalyzed benzylation of aldimine esters is reported. A series of benzyl-substituted α-quaternary amino acids could be synthesized in high yield and with high levels of enantioselectivity (up to 90 % yield and 99 % ee). The experimental and theoretical calculation results suggested that the strong electrophilicity of the η -benzylnickel intermediate is crucial for the high reactivity, enabling the reaction under base-free conditions.

Stereodivergent Desymmetrization of Simple Dicarboxylates via Branch-Selective Pd/Cu Catalyzed Allylic Substitution.

Asymmetric desymmetrization has been demonstrated to be a powerful strategy for building stereocenters in asymmetric synthesis. Herein, a Pd/Cu catalyzed asymmetric desymmetrization reaction with a simple geminal dicarboxylate is reported. A wide scope of imino esters bearing an aryl or heteroaromatic group were compatible with this bimetallic catalytic system.

Enantio- and Diastereodivergent Synthesis of Spirocycles through Dual-Metal-Catalyzed [3+2] Annulation of 2-Vinyloxiranes with Nucleophilic Dipoles.

The development of efficient and straightforward methods for obtaining all optically active isomers of structurally rigid spirocycles from readily available starting materials is of great value in drug discovery and chiral ligand development. However, the stereodivergent synthesis of spirocycles bearing multiple stereocenters remains an unsolved challenge owing to steric hindrance and ring strain. Herein, we report an enantio- and diastereodivergent synthesis of rigid spirocycles through dual-metal-catalyzed [3+2] annulation of oxy π-allyl metallic dipoles with less commonly employed nucleophilic dipoles (imino esters).

Synergistic Ir/Cu Catalysis for Asymmetric Allylic Alkylation of Oxindoles: Enantio- and Diastereoselective Construction of Quaternary and Tertiary Stereocenters.

3,3-Disubstituted oxindoles bearing quaternary and tertiary stereogenic centers are privileged structural motifs, which widely exist in pharmaceutical and natural products. Herein, a highly regio-, enantio-, and diastereoselective allylic alkylation of 3-alkyl oxindoles through synergistic iridium and copper catalysis is described, which provides a series of 3,3-disubstituted oxindole derivatives containing adjacent quaternary and tertiary stereogenic centers in excellent yields, enantiomeric excess, and diastereomeric ratio (for 30 examples, up to 97 % yield, >99 % ee, and >20 : 1 dr). This method provides exclusive branched selectivity, excellent enantio- and diastereoselectivities, and good functional compatibility.

Copper-Catalyzed [2 + 3] Cyclization of α-Hydroxyl Ketones and Arylacetonitriles: Access to Multisubstituted Butenolides and Oxazoles.

A copper-catalyzed [2 + 3] formal cyclization reaction between α-hydroxyl ketones and arylacetonitriles has been developed. The reaction outcome was ultimately dependent on the structure of the α-hydroxy ketones employed. Tertiary α-hydroxy ketones gave 3,4,5,5-tetrasubstituted butenolides as the sole products, while secondary α-hydroxy ketones furnished 2,4,5-trisubstituted oxazoles selectively.

nBuNI-catalyzed oxidative cross-coupling of carbon dioxide, amines, and aryl ketones: access to O-β-oxoalkyl carbamates.

The first nBuNI-catalyzed oxidative cross-coupling reaction of carbon dioxide, amines and arylketones has been successfully developed by using TBHP as the oxidant, providing an efficient, atom-economical and metal-free strategy for the synthesis of a range of O-β-oxoalkyl carbamates.

Base-Promoted Formal [4 + 3] Annulation between 2-Fluorophenylacetylenes and Ketones: A Route to Benzoxepines.

The first base-promoted formal [4 + 3] annulation between 2-fluorophenylacetylenes and ketones has been disclosed. The reaction proceeds through a tandem α-vinylation of ketones followed by an intramolecular nucleophilic aromatic substitution (SNAr) reaction of the in situ generated β,γ-unsaturated ketone intermediates, providing a straightforward access to a wide range of functionalized benzoxepines in moderate to high yields. The transition-metal-free methodology featured a wide substrate scope, the use of easily available starting materials, and a high functional group tolerance.

Base-promoted coupling of carbon dioxide, amines, and diaryliodonium salts: a phosgene- and metal-free route to O-aryl carbamates.

A phosgene- and metal-free synthesis of O-aryl carbamates is realized through a three-component coupling of carbon dioxide, amines and diaryliodonium salts. The reaction only requires a base as the promoter, providing access to a diverse array of O-aryl carbamates in moderate to high yields with excellent chemoselectivity.

[Gossypol decreases the expression of connexin 43 in Sertoli cells].

Objective: To study the effect of gossypol on the expression of connexin 43 (CX43) in Sertoli cells.

Methods: TM4 Sertoli cells were cultured and treated with gossypol at the concentrations of 1.25, 2.