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

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-center dot(-) 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-center dot(-) 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.