A Practically Unified Electrochemical Strategy for Ni-Catalyzed Decarboxylative Cross-Coupling of Aryl Trimethylammonium Salts

When transition-metal catalysis meets electrosynthesis: a recent update

While aiming at sustainable synthesis, organic electrosynthesis has attracted increasing attention in the past few years. In parallel, with a deeper understanding of catalyst and ligand design, 3d transition-metal catalysis allows the conception of more straightforward synthetic routes in a cost-effective fashion. Owing to their intrinsic advantages, the merger of organic electrosynthesis with 3d transition-metal catalysis has offered huge opportunities for conceptually novel transformations while limiting ecological footprint. This review summarizes the key advancements in this direction published in the recent two years, with specific focus placed on strategy design and mechanistic aspects.

Electrochemical oxidative decarboxylative of α-oxocarboxylic acids towards the synthesis of quinazolines and quinazolinones

A mild and environmentally electrochemical method for the synthesis of quinazolines and quinazolinones has been developed through anodic oxidation decarboxylative of α-oxocarboxylic acids. The present reaction was efficiently conducted by using simple and cheap NH4I as the N-source and electrolyte in an undivided cell. The desired products, quinazolines and quinazolinones, were isolated in high yield under chemical oxidant free conditions.

Electrochemical Decarboxylative Alkoxy-alkoxycarbonylation of Alkenes

A method is presented for decarboxylative alkoxy-alkoxycarbonylation of various alkenes with alcohols by electrochemical anodic oxidation of monopotassium ethyloxalate salts with good functional group compatibility. The reaction involves anodic oxidation to form an acyl radical, followed by addition to an olefin to yield a new alkyl radical, which is anodically oxidized to a carbon cation and captured by alcohols to afford β-alkoxyalkanoates. Adding catalytic amounts of ammonium iodide enhanced the efficiency of the reactions.

Organomediated electrochemical fluorosulfonylation of aryl triflates via selective C-O bond cleavage

Although aryl triflates are essential building blocks in organic synthesis, the applications as aryl radical precursors are limited. Herein, we report an organomediated electrochemical strategy for the generation of aryl radicals from aryl triflates, providing a useful method for the synthesis of aryl sulfonyl fluorides from feedstock phenol derivatives under very mild conditions. Mechanistic studies indicate that key to success is to use catalytic amounts of 9, 10-dicyanoanthracene as an organic mediator, enabling to selectively active aryl triflates to form aryl radicals via orbital-symmetry-matching electron transfer, realizing the anticipated C-O bond cleavage by overcoming the competitive S-O bond cleavage. The transition-metal-catalyst-free protocol shows good functional group tolerance, and may overcome the shortages of known methods for aryl sulfonyl fluoride synthesis. Furthermore, this method has been used for the modification and formal synthesis of bioactive molecules or tetraphenylethylene (TPE) derivative with improved quantum yield of fluorescence.

Palladium-catalysed deaminative/decarboxylative cross-coupling of organoammonium salts with carboxylic acids

A palladium-catalysed carbon-carbon bond-forming reaction via deaminative/decarboxylative cross-coupling of organoammonium salts with carboxylic acids was developed. Under the reaction conditions, polyfluoroaromatic carboxylic acids, propiolic acids and α-cyano benzyl carboxylic acid reacted smoothly with benzyl ammonium salts to produce the corresponding carbon-carbon coupling products in good-to-excellent yields.

Selective Fluorosulfonylation of Thianthrenium Salts Enabled by Electrochemistry

A practical electrochemically driven method for fluorosulfonylation of both aryl and alkyl thianthrenium salts has been disclosed. The strategy does not need external redox reagents or metal catalysts. In combination with C-H thianthrenation of aromatics, this method provides a new tool for the site-selective fluorosulfonylation of drugs.

Nickel(II)-catalyzed highly selective 1,2-diborylation of non-activated monosubstituted alkenes

A practical method for 1,2-diborylation of non-activated monosubstituted alkenes via nickel catalysis has been developed. The protocol features high functional group tolerance and can be applied for the formal synthesis of drugs and modification of natural product derivatives. Preliminary mechanistic studies imply the involvement of a Ni(II) catalytic cycle.

Manganese-mediated reductive N,N-dialkylation of nitroarenes: a dramatic NiI2 effect

A dramatic NiI2 effect has been found for Mn-mediated reductive N,N-dialkylation of nitroaromatics.