Electrochemical oxo-functionalisation of cyclic alkanes and alkenes using nitrate and oxygen

Abstract

Direct functionalization of C(sp3)–H bonds allows a fast, synthetic access to valuable products, starting from simple petrochemicals. Chemical transformation of inactivated methylene groups, however, remains challenging for organic synthesis. Here, we present a general electrochemical method for the oxidation of C(sp3)–H and C(sp2)–H bonds, in which cyclic alkanes and (cyclic) olefins are converted into cycloaliphatic ketones as well as aliphatic (di)carboxylic acids. This resource-friendly method is based on nitrate salts in a dual role as anodic mediator and supporting electrolyte, which can be fully recovered and recycled. Reduction of molecular oxygen as cathodic counter reaction leads to an efficient convergent use of both electrode reactions. By avoiding the use of transition metals and chemical oxidisers, this protocol represents a sustainable oxo-functionalization method, leading to a valuable contribution for the sustainable conversion of petrochemical feedstocks into synthetically usable fine chemicals and commodities.

Addressing the Challenge of Electrochemical Ionomer Oxidation in Future Anion Exchange Membrane Water Electrolyzers

“…Electrochemical oxidation of cyclic alkanes and cyclic olefins such as norbornene occurs at ∼1.0 V, producing cycloaliphatic ketones and aliphatic (di)carboxylic acids (Figure 1e). 32 Electrochemical oxidation of heterocycles, such as imidazole, indoles, or pyridine, occurs at relatively high (>1.5 V) and also varies based on the chemical environment. 33,34 Only unsaturated hydrocarbons (olefins) (oxidation potential: 1.9−2.8 V) and unactivated hydrocarbons (alkanes) (oxidation potential: > 2.7 V) might have sufficient electrochemical stability under the working voltage of AEMWEs.…”