Electrochemical four-component aminochlorination tuned by benzimidazoles

Abstract

Aminochlorination of alkenes has received a tremendous amount of attention from the academic and industrial communities, as it allows direct and general access to functionalized amines. However, conventional approaches commonly require transition-metal catalysts, and environmentally unfriendly chlorinating regents, which severely restrict its practical application. Herein, we report an electrochemical solution for a ‘green’ aminochlorination of alkenes, in which solvent acetonitrile and inorganic salt MgCl₂ readily served as nitrogen and chlorine sources, respectively. More importantly, benzimidazole was demonstrated to be a reactivity modulator for chlorine radicals in the reaction. With the in situ generation of various N-chlorobenzimidazole species, tunable reactivity, chemoselectivity and stereoselectivity were readily achieved in the four-component reaction. Specifically, 1,2- and 1,4-aminochlorination of the diene were selectively accessed by simply varying benzimidazole variants. Meanwhile, the slow-releasing chlorinating reagent exhibited more robust and reliable reactivity compared to an isolated reagent, and tolerated the aminochlorination of alkynes. Additionally, we propose a plausible reaction pathway to rationalize the experimental observations.