Electrochemical Cross-Coupling between N-(4-Hydroxyphenyl)-sulfonamides and 2-Naphthols: Synthesis of 2,2'-Bis(arenol)s.

We herein present an electrochemical method for the dehydrogenative cross-coupling of N-(4-hydroxyphenyl)-sulfonamides and 2-naphthols. This transformation provides a direct and scalable approach to a wide range of C1-symmetric 2,2'-bis(arenol)s with moderate to high yields under mild conditions. Preliminary attempts with the asymmetric variant of this reaction were also performed with ≤55% ee for the synthesis of 2,2'-bis(arenol)s. Control experiments were conducted to propose a plausible mechanism for the reaction.

A TEMPO promoted tandem reaction of 2-aminobenzophenones and benzylamines under electrochemical conditions.

This study describes the efficient synthesis of quinazolines promoted by TEMPO via electro-catalysis with 2-aminobenzophenones and benzylamines. The method exhibited remarkable chemoselectivity under mild reaction conditions. A series of quinazolines could be obtained in moderate to good yields. In addition, control experiments were carried out to verify the reaction mechanism. Furthermore, the synthesis on the gram scale was conducted successfully to give the target product.

Aryliodonium Salt-Induced Regioselective Access to meta-Substituted Anilines by Arylation of Azoles.

A highly efficient aryliodonium salt-induced regioselective access to meta-substituted anilines by arylation of azoles has been developed under catalyst-free conditions. This efficient transformation provides a facile and scalable approach to a wide range of biologically active N-arylazoles with moderate to high yields. According to the control experiments, two plausible pathways, including a Michael pathway and a free radical coupling pathway, for the reaction were proposed.

Recent Advances in Regioselective C-H Bond Functionalization of Free Phenols.

Phenols are important readily available synthetic building blocks and starting materials for organic synthetic transformations, which are widely found in agrochemicals, pharmaceuticals, and functional materials. The C-H functionalization of free phenols has proven to be an extremely useful tool in organic synthesis, which provides efficient increases in phenol molecular complexity. Therefore, approaches to functionalizing existing C-H bonds of free phenols have continuously attracted the attention of organic chemists. In this review, we summarize the current knowledge and recent advances in ortho-, meta-, and para-selective C-H functionalization of free phenols in the last five years.

Recent advances in metal catalyst- and oxidant-free electrochemical C-H bond functionalization of nitrogen-containing heterocycles.

The C-H functionalization of nitrogen-containing heterocycles has emerged as a powerful strategy for the construction of carbon-carbon (C-C) and carbon-heteroatom (C-X) bonds. In order to achieve efficient and selective C-H functionalization, electrochemical synthesis has attracted increasing attention. Because electrochemical anodic oxidation is ideal for replacing chemical reagents in C-H functionalization reactions. This mini-review summarizes the current knowledge and recent advances since 2017 in the synthetic utility of electrochemical transformations for the C-H functionalization of nitrogen-containing heterocycles.

Efficient enantioselective synthesis of trisubstituted γ-lactam via the Michael addition reaction of 2,3-dioxopyrrolidine with indole in aqueous media.

An efficient enantioselective Michael addition reaction of 2,3-dioxopyrrolidine with indole in aqueous media was developed by virtue of a chiral copper complex. This reaction features air tolerance, a broad substrate scope and mild reaction conditions. Furthermore, a gram-scale synthesis was conducted to afford the corresponding products with a high yield and excellent enantioselectivity. Moreover, the proposed mechanism was supported by control experiments, XPS investigation and DFT calculations.

Lewis Acid-Catalyzed Enantioselective Friedel-Crafts Alkylation of Pyrrole in Water.

Highly enantioselective Friedel-Crafts alkylation of pyrroles with 2-enoyl-pyridine N-oxides in water/chloroform (10:1) was developed under catalysis of Lewis acid. The Friedel-Crafts alkylation products can be obtained in high yields and excellent enantioselectivities. Moreover, several control experiments were carried out to study the reaction mechanism.

Copper Catalyzed Diastereo- and Enantioselective 1,4-Addition Michael Reaction of 2,3-Dioxopyrrolidines with Nitroalkanes in Aqueous Media.

A good diastereo- and enantioselective 1,4-addition Michael reaction catalyzed by a chiral copper complex was developed in aqueous media. A series of nitro-containing pyrrolidones could be gained in high yields with excellent diastereoselectivities and good ee values by virtue of this developed method. It affords a facile access to construct carbon-carbon bonds with water and air tolerance. Furthermore, the gram scale synthesis was conducted successfully to give rise to the corresponding products.

Copper-catalyzed enantioselective Mukaiyama aldol reaction of silyl enol ethers with isatins.

A highly enantioselective Mukaiyama aldol reaction of silyl enol ethers with isatins catalyzed by chiral copper complexes was developed. A series of chiral 3-substituted 3-hydroxy-2-oxindoles bearing a tetra-substituted center could be obtained exclusively with high yields (up to 95%) and excellent enantioselectivities (up to 99%). In particular, water was essential to improve the diastereoselectivity.

Enantioselective Hetero-Diels-Alder Reaction and the Synthesis of Spiropyrrolidone Derivatives.

An efficient enantioselective hetero-Diels-Alder reaction was developed under catalysis of a chiral copper complex. A variety of spiropyrrolidones, which bear a tetra-substituted carbon stereocenter, can be obtained in good yields with excellent enantioselectivities by virtue of this method. Furthermore, a substrate-dependent reaction pathway was proposed on the basis of the isolated intermediates.

Copper-Catalyzed Enantioselective Henry Reaction of ß,γ-Unsaturated α-Ketoesters with Nitromethane in Water.

A highly enantioselective Henry reaction of ß,γ-unsaturated α-ketoesters with nitromethane in water by virtue of chiral copper complexes has been developed. A series of unsaturated ß-nitro-α-hydroxy esters bearing tetrasubstituted carbon stereocenters were obtained exclusively with high yields and excellent enantioselectivities. This method could avoid tedious anaerobic anhydrous manipulation and reduce the environmental pollution caused by organic solvents.

Iodine-catalyzed direct C-H thiolation of imidazo[1,5-a]quinolines for the synthesis of 3-sulfenylimidazo[1,5-a]quinolines.

An iodine-catalyzed regioselective sulfenylation of imidazo[1,5-a]quinolines was developed under metal- and oxidant-free reaction conditions. Using disulfides or thiophenols as sulfenylating agents, 3-sulfenylimidazo[1,5-a]quinoline derivatives were obtained in good to excellent yields with broad functional group tolerance. A multi-component reaction to generate 1-sulfenylated imidazo[1,5-a]pyridines is also described. Preliminary biological evaluation showed that some of the 3-sulfenylated imidazo[1,5-a]quinolines had significant anticancer activity.