Selective electrochemical generation of benzylic radicals enabled by ferrocene-based electron-transfer mediatorsElectronic supplementary information (ESI) available: Experimental details, procedures and spectroscopic characterisations. See DOI: 10.1039/c7sc04032f

The generation and intermolecular functionalisation of carbon-centred radicals has broad potential synthetic utility. Herein, we show that benzylic radicals may be generated electrochemically from benzylboronate derivatives at low electrode potentials ( ca. −0.3 V vs. Cp 2 Fe 0/+ ) via single electron oxidation. Use of a catalytic quantity of a ferrocene-based electron-transfer mediator is crucial to achieve successful radical functionalisation and avoid undesirable side reactions arising from direct electrochemical oxidation or from the use of stoichiometric ferrocenium-based oxidants. The use of ferrocene mediators offers significant advantages over direct electrolysis in the generation and functionalization of radicals from benzylboronates.