DYNO-MILL Mechanochemistry Enables Diaziridine-Mediated Access to Unsymmetrical Azobenzenes and Electrochemical Tetrazole Synthesis.

Abstract

We report a catalyst-, acid-, and base-free strategy for activation of an N-N-containing diaziridine/diazo-derived framework enabling the synthesis of unsymmetrical azobenzenes via a mechanochemical three-component reaction in a horizontal bead mill (DYNO-MILL). The process proceeds through in situ formation of a diaziridine intermediate from a formal 2 + 1 annulation of diazo esters and dialkyl azodicarboxylates, followed by electrophile-induced N─N bond reorganization with aryl diazonium tetrafluoroborates. This solvent-minimized, operationally simple protocol tolerates air and moisture and is scalable. The resulting azobenzenes serve as versatile substrates for oxidant-free electrochemical conversion to substituted tetrazoles without chromatographic purification. Green metrics analysis for the tetrazole formation reveals a significant improvement in atom economy (77.33%) compared to literature methods (29.98%-34.96%) and an enhanced Eco-Scale score (73), highlighting the sustainability of this approach.