Electrochemical synthesis of sulfonamides in single-pass flow

Abstract

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.