关键词: 电化学催化, 自由基路径, 交叉偶联放氢, 亚磺酰胺

Catalytic synthesis of organic sulfinamides has great significance and value in organic synthesis, material science, and bioscience. Traditional synthetic methods for sulfinamides are often confronted with various challenges, such as tedious reaction steps, harsh reaction conditions. Direct activation of S—H and N—H bonds to synthesis sulfinamides is the most effective and atomic economic way, which can realize the N—S bonds construction without pre-functionalization of the substrates. To establish a versatile and efficient technology for such reaction, an electrochemical cross coupling hydrogen evolution (CCHE) reaction, which is often used as an environmentally friendly and efficient way to construct new bonds, for synthesis of sulfinamides has been successfully developed by using thiols and amines as the easily available and inexpensive substrates. A series of sulfinamides were prepared with excellent yields and good compatibility of functional groups under extremely mild reaction conditions. Experimental results showed that sulfenamides, which were constructed as intermediate products via radical pathway, were further oxidized to sulfinamides. H₂ ¹⁸O labeling experiment confirmed that the oxygen of sulfinyl group comes from the trace water in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). In addition, tetrabutylammonium iodide (TBAI) played important dual roles of intermediate and electrolyte in this reaction system. The typical procedure is as follows: A 20 mL oven-dried reaction vital equipped with a magnetic stir bar was charged with thiol 1 (0.2 mmol), amine 2 (0.3 mmol) and TBAI (0.05 mol/L) in HFIP (5 mL), and exhausted via puncture needle for 15 minutes with argon. The mixture was then electrolysed with carbon foam plate (anode) and platinum plate (cathode) as the electrodes in an undivided cell for 6 hours in 10 mA constant current at room temperature. After the reaction, the mixture was evaporated under reduced pressure to remove the solvent and the residue was purified by chromatography on silica gel to get the desired sulfinamide 3.

Key words: electrochemical catalysis, radical pathway, cross coupling hydrogen evolution, sulfinamides