Organolithium-Mediated Conversion of Aryl Azides to Aryltriazenes in Deep Eutectic Solvents

Typically, the reaction between aryl azides and Grignard reagents in diethyl ether at room temperature leads to the formation of N‑alkylanilines. When the temperature is lowered to 0 °C, the use of either Grignard or organolithium reagents shifts the reactivity toward the formation of aryltriazenes–valuable intermediates in organic synthesis. Notably, Gandelman and co-workers have employed diaryltriazenes in innovative “triazenolysis” protocols for the generation of amines from alkenes3. In addition, these species are versatile precursors for the synthesis of benzotriazoles. Our group has long been engaged in the study of polar organometallic reactivity in bio‑inspired solvents such as water and Deep Eutectic Solvents (DESs). Building on this expertise, we investigated the potential of DESs as green reaction media for the alkylation of aryl azides with organolithium reagents. Interestingly, this new protocol also proved efficient for the synthesis of both dialkyl- and monoalkyltriazenes – species that are typically difficult to access via classic diazonium coupling, due to their tendency to undergo overreaction with diazonium ions to give undesired penta-azadienes. Given the intrinsic challenges in purifying triazenes, we’re further exploring their utility as intermediates in one-pot benzotriazoles synthesis conducted in DESs.