Anodic Coupling Reactions Research Articles

Electrocatalytic C−N Couplings at Cathode and Anode

AbstractElectrocatalytic C−N couplings are promising alternatives to construct C−N bonds and to synthesize vital chemicals, including amine, amide, amino acid, oxime, imine, and nitrile, under ambient conditions. In recent years, the electrocatalytic C−N coupling has attracted a wide range of research interest and has achieved considerable developments. Here, the electrocatalytic C−N coupling is systematically reviewed aiming at reductive cathode and oxidative anode. In the cathodic part, the electrocatalytic coupling reaction systems, the corresponding design principles of electrocatalysts for different reaction systems, the mechanism studies from experimental and theoretical aspects, and the application‐oriented electrocatalytic devices for electrocatalytic C−N couplings are summarized. Anodic C−N coupling offers a potential approach to replace the conventional energy‐demand synthesis protocols, and is an indispensable part of the green and controllable construction of unsaturated C = N and C≡N bonds. According to the principle that electron transfer is the crucial point in anodic C−N coupling, the anodic coupling reactions are sorted out based on the direct and the indirect C−N coupling paths, respectively. Finally, the challenges and outlooks in this field are proposed. Electrocatalytic C−N coupling is an appealing research topic in electrochemistry and possesses infinite possibilities in the future.

Supporting Electrolyte-Free Electrochemical Oxidative C-H Sulfonylation and Thiocyanation of Fused Pyrimidin-4-Ones in an All-Green Electrolytic System.

An electrooxidative C-H functionalization is a widely accepted route to obtain sulfur-containing arenes and heteroarenes. However, this process often involves using non-recyclable supporting electrolytes, (co)solvents like hexafluoroisopropanol, additives like acid, or catalysts. The use of additional reagents can increase costs and waste, reducing atom efficiency. Moreover, unlike other nitrogen-containing heterocycles, there have only been sporadic reports of electrochemical C-H functionalization in fused pyrimidin-4-ones, and an electrolyte-free process has yet to be developed. This work demonstrates that such anodic coupling reactions can be performed in an all-green electrolytic system without using such additional electrolytes or HFIP, maintaining a high atom economy. This C-H functionalization strategy utilizes inexpensive sodium sulfinates and ammonium thiocyanate as sulfonylating and thiocyanating agents in an undivided cell at a constant current, using a mixture of CH3 CN/H2 O as solvent at room temperature. Thus, fused pyrimidin-4-ones can be selectively converted into C3-sulfonylated and -thiocyanated derivatives in moderate to good yields.

Single and Twofold Metal- and Reagent-Free Anodic C-C Cross-Coupling of Phenols with Thiophenes.

The first electrochemical dehydrogenative C-C cross-coupling of thiophenes with phenols has been realized. This sustainable and very simple to perform anodic coupling reaction enables access to two classes of compounds of significant interest. The scope for electrochemical C-H-activating cross-coupling reactions was expanded to sulfur heterocycles. Previously, only various benzoid aromatic systems could be converted, while the application of heterocycles was not successful in the electrochemical C-H-activating cross-coupling reaction. Here, reagent- and metal-free reaction conditions offer a sustainable electrochemical pathway that provides an attractive synthetic method to a broad variety of bi- and terarylic products based on thiophenes and phenols. This method is easy to conduct in an undivided cell, is scalable, and is inherently safe. The resulting products offer applications in electronic materials or as [OSO]2- pincer-type ligands.

Anodic Coupling Reactions: Exploring the Generality of Curtin−Hammett Controlled Reactions

Intramolecular anodic olefin coupling reactions can be compatible with the presence of dithioketal protecting groups even though the dithioketal oxidizes at a lower potential than either of the groups participating in the cyclization. In such cases, product formation is controlled by the Curtin-Hammett Principle. In this study, the generality of such reactions is examined along with the use of alternative reaction conditions to suppress unwanted side reactions.

ChemInform Abstract: Anodic Coupling Reactions and the Synthesis of C‐Glycosides.

AbstractBoth furanose and pyranose derivatives containing a masked aldehyde functional group can be prepared by the anodic coupling reaction between an electron‐rich olefin and an alcohol.

Anodic Coupling Reactions and the Synthesis of C-Glycosides

A convenient, two-step procedure has been developed for converting sugar derivatives into C-glycosides containing a masked aldehyde functional group. The chemistry takes advantage of an anodic coupling reaction between an electron-rich olefin and an alcohol. The sequence works for the formation of both furanose and pyranose derivatives if less polarized vinyl sulfide derived radical cation intermediates are used. With more polarized enol ether derived radical cations, the cyclizations work best for the formation of furanose derivatives where the rate of five-membered ring formation precludes elimination reactions triggered by the radical cation.

Anodic Coupling Reactions: A Sequential Cyclization Route to the Arteannuin Ring Skeleton

A pair of intramolecular anodic olefin coupling reactions has been used to construct the arteannuin ring skeleton. Both coupling reactions took advantage of a furan ring as one of the coupling partners. In the first, it was found that an enol ether derived from an aldehyde was not an effective initiating group for the reaction. Instead, the cyclization benefited strongly from the use of a N,O-ketene acetal initiating group. In the second cyclization, an endocyclic enol ether was coupled to the furan ring. This second electrolysis reaction generated the key tetrasubstituted carbon at the center of the arteannuin ring skeleton.

Oxidative Cyclization Reactions: Amide Trapping Groups and the Synthesis of Furanones

Intramolecular anodic coupling reactions involving ketene dithioacetal radical cations and amide trapping groups have been examined. The reactions generate furanone products and benefit greatly from the addition of water to the reaction medium. The cyclization reactions lead to products having stereochemistry that is directly analogous to oxidative cyclization reactions utilizing ketene dithioiacetal radical cations and alcohol trapping groups. [reaction: see text]

Anodic Coupling Reactions: The Use of N,O‐Ketene Acetal Coupling Partners.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Anodic Olefin Coupling Reactions Involving Ketene Dithioacetals: Evidence for a “Radical‐Type” Cyclization.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Anodic olefin coupling reactions involving ketene dithioacetals: evidence for a ‘radical-type’ cyclization

A series of anodic coupling reactions between ketene dithioacetal groups and enol ethers have been studied in order to probe why some of the cyclizations are successful while other closely related attempts fail. It has been found that the success of the cyclization reactions strongly depends on the location of substituents on the olefins. The reactions are highly sensitive to substituents on the terminating olefin but not to substituents on the initial radical cation. This behavior is consistent with what has been observed previously with radical cyclization reactions.

Anodic coupling reactions: probing the stereochemistry of tetrahydrofuran formation. A short, convenient synthesis of linalool oxide.

[reaction: see text]. Intramolecular coupling reactions between enol ether radical cations and oxygen nucleophiles are primarily governed by stereoelectronics. By taking advantage of this observation, a tetrahydrofuran building block for use in constructing (+)-linalool oxide and rotundisine has been synthesized in four steps from a commercially available starting material. The synthesis of (+)-linalool oxide has been completed.

Electrochemical and spectroscopic properties of new functionalized polythiophenes electroformed from the oxidation of dithienyls linked by long chain polyether spacers

Abstract Polyethers possessing two 3-thienyl units have been synthesized and their electrochemical behaviour has been investigated. In electropolymerization of these symmetrical compounds is found to consume two electrons per molecule of substrate for the polymer formation and 0.65 electron per molecule for the doping. Such a result demonstrates that half of thiophene units is involved in electropolymerization process and that the as-grown material would be a redox-type polymer, composed of electroactive oligothiophenes units linked together by polyether chains, alone or mixed with an electronically conducting polymer possessing pendant polyether chains. As demonstrated by the UV-visible spectroscopy and cyclic voltammetry experiments, further anodic coupling reactions can be performed potentiostatically and lead to a more distorted material possessing macrocyclic cavities.

Electrochemical oxidation of aromatic ethers. Part 10. Regioselectivity in the aryl–aryl coupling reactions of some 4-benzylisochroman-3-ones and benzyl-1,2,3,4-tetrahydroisoquinolines.

The anodic coupling reactions of 4-benzylisochroman-3-ones, 1- and 4-benzyl-1,2,3,4-tetrahydro-isoquinolines are compared and analysed. In neutral media 4-benryltetrahydroisoquinolines may afford products resulting from coupling to C-1 and/or to N-2 depending on the ring substituents. In acidic solution 4-benzyltetrahydroisoquinolines yield isoaporphines whereas their 1-benzyl analogues couple at C-8a to give morphindienones. This difference may be explained by considering the inductive effects inherent in the protonated forms of the bases. 4-Benzylisochroman-3-ones also couple at C-8a, but the intermediates thus produced are unstable and either rearrange or react with available nucleophiles.