Electrochemical Cyclization of o -Aminyl Azobenzenes: Roles of Aldehydes in N-N Bond Cleavage.

Direct functionalization of azobenzenes provides an approach to obtaining valuable molecules in synthetic chemistry. However, an efficient method for the cleavage of the N═N bond of azobenzenes, which is a key process for this transformation, is still lacking. We herein disclose an electrochemical reduction-induced cyclization of azobenzenes with aldehydes via N═N bond cleavage. This electrochemical cyclization of azobenzenes proceeds well in the absence of any transition metals or external chemical oxidants, leading to the formation of N-protected benzimidazoles in moderate to good yields.