Modern Electrochemical Aspects for the Synthesis of Value‐Added Organic Products

The use of electricity instead of stoichiometric amounts of oxidizers or reducing agents in synthesis is very appealing for economic and ecological reasons, and represents a major driving force for research efforts in this area. To use electron transfer at the electrode for a successful transformation in organic synthesis, the intermediate radical (cation/anion) has to be stabilized. Its combination with other approaches in organic chemistry or concepts of contemporary synthesis allows the establishment of powerful synthetic methods. The aim in the 21st Century will be to use as little fossil carbon as possible and, for this reason, the use of renewable sources is becoming increasingly impo…

Innenrücktitelbild: Metall- und reagensfreie dehydrierende formale Benzyl-Aryl-Kreuzkupplung durch anodische Aktivierung in 1,1,1,3,3,3-Hexafluorpropan-2-ol (Angew. Chem. 37/2018)

Elektrifizierung der organischen Synthese

ChemInform Abstract: Access to Pyrazolidin-3,5-diones Through Anodic N-N Bond Formation.

Pyrazolidin-3,5-diones are important motifs in heterocyclic chemistry and are of high interest for pharmaceutical applications. In classic organic synthesis, the hydrazinic moiety is installed through condensation using the corresponding hydrazine building blocks. However, most N,N'-diaryl hydrazines are toxic and require upstream preparation owing to their low commercial availability. We present an alternative and sustainable synthetic approach to pyrazolidin-3,5-diones that employs readily accessible dianilides as precursors, which are anodically converted to furnish the N-N bond. The electroconversion is conducted in a simple undivided cell under constant-current conditions.

Metal- and Reagent-Free Dehydrogenative Formal Benzyl-Aryl Cross-Coupling by Anodic Activation in 1,1,1,3,3,3-Hexafluoropropan-2-ol

A selective dehydrogenative electrochemical functionalization of benzylic positions that employs 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP) has been developed. The electrogenerated products are versatile intermediates for subsequent functionalizations as they act as masked benzylic cations that can be easily activated. Herein, we report a sustainable, scalable, and reagent- and metal-free dehydrogenative formal benzyl-aryl cross-coupling. Liberation of the benzylic cation was accomplished through the use of acid. Valuable diarylmethanes are accessible in the presence of aromatic nucleophiles. The direct application of electricity enables a safe and environmentally benign chemical transformati…

Moderne Aspekte der Elektrochemie zur Synthese hochwertiger organischer Produkte

Electrochemical synthesis of benzoxazoles from anilides - a new approach to employ amidyl radical intermediates.

A novel electrochemical method for the synthesis of benzoxazoles from readily available anilides is reported. Various functionalities are tolerated and good yields can be achieved. By employing common electrode materials and a simple constant current protocol, this method is an attractive new alternative to conventional pathways.

One-step synthesis of multi-alkyne functional hyperbranched polyglycerols by copolymerization of glycidyl propargyl ether and glycidol

By copolymerization of glycidol with the alkyne-containing oxirane monomer glycidyl propargyl ether (GPE), hyperbranched polyglycerol (hbPG) with a defined number of alkyne functionalities (up to 38%) can be obtained in a one-step procedure. The number of alkynes can be adjusted by the glycidol/GPE ratio to provide multi-alkyne functional hbPGs, maintaining the highly branched polyether structure. Interestingly, the acidic proton of the alkyne moiety does not interfere with the proton exchange mechanism during the polymerization of glycidol. By specific modification of the synthesis procedure, crosslinking reactions can be suppressed. The polymers exhibit molecular weights ranging from 1800…

Metall- und reagensfreie dehydrierende formale Benzyl-Aryl-Kreuzkupplung durch anodische Aktivierung in 1,1,1,3,3,3-Hexafluorpropan-2-ol

Inside Back Cover: Metal- and Reagent-Free Dehydrogenative Formal Benzyl-Aryl Cross-Coupling by Anodic Activation in 1,1,1,3,3,3-Hexafluoropropan-2-ol (Angew. Chem. Int. Ed. 37/2018)

Electrochemical Formation of 3,5-Diimido-1,2-dithiolanes by Dehydrogenative Coupling

A synthetic approach to the cyclic disulfide moiety of 3,5-diimido-1,2-dithiolane derivatives starting with readily available precursors including the electrochemical coupling of dithioanilides is developed. The electrochemical key step provides sustainable synthetic access in high yields, using a very simple electrolysis setup.

Insights into the Mechanism of Anodic N–N Bond Formation by Dehydrogenative Coupling

The electrochemical synthesis of pyrazolidine-3,5-diones and benzoxazoles by N-N bond formation and C,O linkage, respectively, represents an easy access to medicinally relevant structures. Electrochemistry as a key technology ensures a safe and sustainable approach. We gained insights in the mechanism of these reactions by combining cyclovoltammetric and synthetic studies. The electron-transfer behavior of anilides and dianilides was studied and led to the following conclusion: The N-N bond formation involves a diradical as intermediate, whereas the benzoxazole formation is based on a cationic mechanism. Besides these studies, we developed a synthetic route to mixed dianilides as starting m…

Direct electrochemical generation of organic carbonates by dehydrogenative coupling.

Organic carbonates are an important source for polycarbonate synthesis. However, their synthesis generally requires phosgene, sophisticated catalysts, harsh reaction conditions, or other highly reactive chemicals. We present the first direct electrochemical generation of mesityl methyl carbonate by C–H activation. Although this reaction pathway is still challenging concerning scope and efficiency, it outlines a new strategy for carbonate generation.

Electrifying Organic Synthesis

Abstract The direct synthetic organic use of electricity is currently experiencing a renaissance. More synthetically oriented laboratories working in this area are exploiting both novel and more traditional concepts, paving the way to broader applications of this niche technology. As only electrons serve as reagents, the generation of reagent waste is efficiently avoided. Moreover, stoichiometric reagents can be regenerated and allow a transformation to be conducted in an electrocatalytic fashion. However, the application of electroorganic transformations is more than minimizing the waste footprint, it rather gives rise to inherently safe processes, reduces the number of steps of many synth…

CCDC 1840041: Experimental Crystal Structure Determination

Related Article: Yasushi Imada, Johannes L. Röckl, Anton Wiebe, Tile Gieshoff, Dieter Schollmeyer, Kazuhiro Chiba, Robert Franke, Siegfried R. Waldvogel|2018|Angew.Chem.,Int.Ed.|57|12136|doi:10.1002/anie.201804997

CCDC 1561793: Experimental Crystal Structure Determination

Related Article: Tile Gieshoff, Anton Kehl, Dieter Schollmeyer, Kevin D. Moeller, Siegfried R. Waldvogel|2017|J.Am.Chem.Soc.|139|12317|doi:10.1021/jacs.7b07488

CCDC 1561794: Experimental Crystal Structure Determination

Related Article: Tile Gieshoff, Anton Kehl, Dieter Schollmeyer, Kevin D. Moeller, Siegfried R. Waldvogel|2017|J.Am.Chem.Soc.|139|12317|doi:10.1021/jacs.7b07488

CCDC 1561792: Experimental Crystal Structure Determination

Related Article: Tile Gieshoff, Anton Kehl, Dieter Schollmeyer, Kevin D. Moeller, Siegfried R. Waldvogel|2017|J.Am.Chem.Soc.|139|12317|doi:10.1021/jacs.7b07488

CCDC 1530094: Experimental Crystal Structure Determination

Related Article: Tile Gieshoff, Anton Kehl, Dieter Schollmeyer, Kevin D. Moeller, Siegfried R. Waldvogel|2017|Chem.Commun.|53|2974|doi:10.1039/C7CC00927E

CCDC 1866690: Experimental Crystal Structure Determination

Related Article: Valentina M. Breising, Tile Gieshoff, Anton Kehl, Vincent Kilian, Dieter Schollmeyer, Siegfried R. Waldvogel|2018|Org.Lett.|20|6785|doi:10.1021/acs.orglett.8b02904

CCDC 1840040: Experimental Crystal Structure Determination

Related Article: Yasushi Imada, Johannes L. Röckl, Anton Wiebe, Tile Gieshoff, Dieter Schollmeyer, Kazuhiro Chiba, Robert Franke, Siegfried R. Waldvogel|2018|Angew.Chem.,Int.Ed.|57|12136|doi:10.1002/anie.201804997