Direct Electrochemical Oxidation of Benzylic C–H Bond by La₂O₃@C/CP Composite Electrode with Water as the Green Oxygen Source

Abstract

Selective oxidation of high-energy C−H bonds to produce carbonyl compounds is a fundamental transformation in fine chemical synthesis. Despite tremendous efforts, the development of green and safe strategies often suffers from harsh reaction conditions and uses homogeneous transition-metal catalysts. Herein, we present an electrochemical oxidation strategy that is green and safe for the direct oxidation of benzylic C−H bonds using La 2 O 3 nanoparticles supported on a carbon paper (La 2 O 3 /CP) anode. La 2 O 3 /CP can selectively oxidize indane to indanone in 83% yield with 73% Faraday efficiency at room temperature. It also can oxidize different kinds of compounds with benzyl C−H bonds to produce the corresponding ketones with moderate-to-excellent yields. The oxygen source was confirmed to be water by an oxygen isotope ( 18 O) tracer experiment. Additionally, the La 2 O 3 @ C/CP composite electrode was reconfigured through carbonizing oleic acid to stabilize La 2 O 3 on CP, resulting in an improved stability due to the reinforced catalyst embedding on CP, and retaining 81% initial activity after five cycles.

DMAP-promoted oxidative functionalization of α-amino ketones via oxygen delivery from water/alcohols

“…Recently, an efficient electrochemical approach for C–H oxidation to a carbonyl group has been demonstrated without separation of alcohol intermediates, while using water as the oxygen source (Scheme 1b, left). 4 As the strategy raises convenience and cost concerns with the utilization of electrochemical devices and expensive electrolyte, there is clearly an urgent demand for new synthetic paradigms, able to achieve direct C–H oxidation to carbonyl groups in a more cost-effective and convenient manner. Inspired by the loss of electrons and protons during the C–H electrooxidation process, we aim to develop an oxidative coupling strategy for direct C–H oxidation using water as an oxygen source in the presence of a proton acceptor, electron acceptor and nucleophilic catalyst (Scheme 1b, right).…”