Self-detachable protecting group function of CO2 in the electrochemical reduction of aryl azides

Abstract

A unique self-detachable protecting group function of CO₂ in the selective electrochemical reduction of azides is reported. By utilizing CO₂ as the self-detachable protecting group, the selective reduction of azides to primary amines is successfully achieved. In contrast, in the absence of CO₂, azides undergo a preferential transformation into formamide derivatives. Due to its stronger electrophilicity than that of DMF, CO₂ preferentially undergoes nucleophilic attack by N˙⁻ generated in situ under electrochemical reduction conditions, thus passivating the nucleophilic ability of the N-site and preventing the formylation process. The function of a self-detachable protecting group is achieved as CO₂ is ultimately released through the spontaneous decarboxylation process, and this process does not require the addition of a deprotection agent. This study also proposes the generation of N˙⁻ through electrochemical reduction of azides. The current findings demonstrate an unconventional application of CO₂, which will stimulate the exploration of novel roles for CO₂ as a non-C1 synthon in electrosynthesis.