Site-selective electrochemical synthesis of nitrogen-enriched bis-pyrazole derivatives: a sustainable approach for N–N versus NN bond formation

Abstract

Two bis-pyrazole derivatives with azo (NN) and dinitrogen (N–N) linkages were synthesized through an electrochemical homo-coupling process, starting from 3,5-diamino-4-cyanopyrazole. Through systematic optimization of electrochemical conditions and electrolytes, we achieved site-selective coupling at the amino or pyrazole nitrogen sites, yielding azopyrazole derivative 2 and N–N homo-coupling product 3. This selective synthesis resulted in high yields of up to 86% for NN bond formation and 78% for N–N bond formation. Cyclic voltammetry studies and radical trapping experiments revealed the critical involvement of amino radicals in the coupling reactions, providing new mechanistic insights. The nitration product of the azo-pyrazole compound exhibits promising detonation properties. This research not only expands the scope of electrochemical synthesis techniques but also offers valuable insights into the reactivity of diverse nitrogen centers within aminopyrazole frameworks. This method presents a potential strategy to enhance the efficiency of synthesizing nitrogen-rich heterocyclic molecules, which are essential in various industrial and technological applications.