Silver nanocluster redox-couple-promoted nonclassical electron transfer: an efficient electrochemical wolff rearrangement of α-diazoketones

Abstract

In this work we report the unique electrocatalytic role of benzoic acid protected silver nanoclusters (Ag_n, mean core diameter 2.5 nm) in the Wolff rearrangement (Scheme 1) of α-diazoketones. More specifically, the presence of a Ag_n⁰/Ag_n⁺ redox couple facilitates a nonclassical electron-transfer process, involving chemical reaction(s) interposed between two electron-transfer steps occurring in opposite directions. Consequently, the net electron transfer between the electron mediator (Ag_n) and α-diazoketone is zero. In-situ UV-visible studies using pyridine as a nucleophilic probe indicate the participation of -ketocarbene/ketene as important reaction intermediates. Controlled potential coulometry of α-diazoketones using Ag_n as the anode results in the formation of Wolff rearranged carboxylic acids in excellent yield, without sacrificing the electrocatalyst.