Enhanced electrocatalytic alcohol oxidation mediated with ultra-low concentration of aminoxyl radicals via an Intermediate-Rich local microenvironment

Abstract

Indirect electrocatalytic alcohol oxidation mediated by aminoxyl radicals generally requires large amounts of aminoxyl radicals to activate the oxidation of alcohols, which limits its potential for industrial utilization. In this study, the cavity structure of carbonaceous nano-volcanoes (CNV) grown on 3D graphite felt as nanoreactors advantageously provides a microenvironment with high compartmentalised reactant concentrations for efficient electrocatalytic alcohol oxidation. By extending the retention time of reactant molecules in the CNV through cavity enrichment, their interaction probability with the electrodes was maximized, resulting in the intensification of mass transport and kinetically favorable settings. Meanwhile, abundant oxygen-containing functional groups on the surface constructed by the CNV provided hydrogen bonding forces to anchor the reactive aminoxyl radicals (4-acetamido-2,2,6,6-tetrame-thylpi-peridin-1-oxyl, ACT) during the reaction. Based on the intermediate-rich local microenvironment, a high turnover frequency of up to 31818 h−1 can be achieved even with only 0.5 mol% ACT-mediated. The electrocatalytic oxidation of benzyl and heterocyclic substrates can be achieved by this method under mild conditions. To showcase the synthetic efficacy and practical applicability of this approach, the successful oxidation of a chiral primary alcohol precursor to the generic drug levetiracetam was demonstrated on a larger scale, presenting further evidence of its practicality and usefulness in chemical synthesis.