Electrochemical Synthesis of Sulfonamides in Single‐Pass Flow

An electrochemical multicomponent synthesis of sulfonamides at room temperature in single‐pass flow is presented. In contrast to batch‐type electrolysis, an undivided flow cell setup with a stainless‐steel cathode and either a boron‐doped diamond (BDD) anode or a glassy carbon anode can be employed. Simply by using SO2 stock solutions, less atom‐economic sulfur dioxide surrogates can be avoided. Moreover, no additional supporting electrolytes are required due to the in‐situ generation of amidosulfinates, which also serve as intermediate for this transformation. This protocol allows sulfonamides to be synthesized directly from non‐prefunctionalized electron‐rich arenes with amines and SO2. In total, 10 examples are demonstrated with isolated yields up to 92 %. The robust scalability of this electrosynthesis with an easy downstream processing was also proven. A scalable electrochemical synthesis of sulfonamides in single‐pass flow in an undivided cell at room temperature has been developed. Stock solutions of sulfur dioxide are utilized as atom‐economic source of SO2, which omits the need for expensive SO2 surrogates.