The critical aspects of the corrosion of metal electrodes in cathodic reductions are covered. We discuss the involved mechanisms including alloying with alkali metals, cathodic etching in aqueous and aprotic media, and formation of metal hydrides and organometallics. Successful approaches that have been implemented to suppress cathodic corrosion are reviewed. We present several examples from electroorganic synthesis where the clever use of alloys instead of soft neat heavy metals and the application of protective cationic additives have allowed to successfully exploit these materials as cathodes. Because of the high overpotential for the hydrogen evolution reaction, such cathodes can contribute toward more sustainable green synthetic processes. The reported strategies expand the applications of organic electrosynthesis because a more negative regime is accessible within protic media and common metal poisons, e.g., sulfur-containing substrates, are compatible with these cathodes. The strongly diminished hydrogen evolution side reaction paves the way for more efficient reductive electroorganic conversions.

In this review,t he versatile and rich chemistry for the electrochemical reductiono fs ubstrates involving N À Ob onds is surveyed. By the cathodic treatment of nitro,n itroso and other oxygenated organic nitrogen substrates,v ersatile andr eactive intermediates are formed which can be subsequently converted to high value-added products. In many examples,n itrogen heterocycles are selectively formed, but, also depending on the electrolytic conditions, free oximes,n itrones,a mines and other entities can be obtained as well. Ther ecent decades have witnessed twom ajor advances-(i)g oing directly to more complext arget molecules and (ii)c onductingt he electrolysesi nm uch simpler set-ups.Both improvements make the cathodic access of the target compoundsm uch more practical and scalable. 1I ntroduction 2N itro Derivatives 2.1 IntermolecularReactions 2.2 IntramolecularReactions:Synthesis of Heterocycles 3O ximes 4O ther Functionalities 5C onclusions

Elevated by the support: 2‐Alkynyl aniline cycloisomerization to indole is catalyzed by cationic Au NPs on a carbon support. Electroneutral and rich 2‐aryl indoles are further converted into 3,3′‐biindoles by oxidative homocoupling that is readily catalyzed by the Au NPs on carbon, and exclusively but also somewhat sluggishly by the carbon support.

Appropriate and fine-tuned treatments of amorphous carbon (AC) involving aqua regia or concentrated HNO 3 leadt oo xidised carbon materials (oAC) which are able to catalyse 2,2'-a nd 3,3'-homocouplings of various functionalised indoles with outstandinga ctivity.T his newly developed carbocatalysed C sp 2 À C sp 2 bondf ormation can be achieved under mild thermalc onditions.T he study on the scope of the reactionr evealed that the reaction can be extended to the homocoupling of other substrates of high synthetic interest such as 2-naphthol, 2-functionalised benzofurans and benzothiofurans. Thec haracterisation of oACw ith XPS together with ad hoc experiments aimeda tb locking the active site revealed that the presence and distribution of C=Of unctionalities is critical and correlates well with the catalytic activity.S uch experiments provide solid support for elucidationo ft he mechanism, suggesting aq uinone nature of the active C= Og roups,w hich are spontaneously regenerated by oxygen. This is confirmed by the fact that 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) is able to promote the coupling in as toichiometricf ashion.

A simple “reagent-free” thermal air treatment turns active carbon into a mildly oxidized material with an increased quinoidic content that catalytically dehydrogenates saturated N-heterocycles to the corresponding aromatic compounds. Additional...