Regioselective Preparation of Allylic Sulfones by Palladium-Catalyzed Reactions of Allylic Nitro Compounds with Sodium Benzenesulfinate

Treatment of allylic nitro compounds with sodium benzenesulfinate in the presence of 5 mol% of Pd(PPh3)4 in N,N-dimethylformamide (DMF) at 20–70 °C for 1–10 h resulted in the formation of allylic sulfones with predominance of kinetically controlled products. The product distribution is mainly controlled by the electronic nature of substituents of an allyl unit, and the isomerization to the thermodynamically-stable isomers is negligible. On the other hand, the palladium-catalyzed sulfonylation of allylic acetates with sodium benzenesulfinate is accompanied by the isomerization to give the thermodynamically-controlled products selectively. These results can be explained by assuming that allylic nitro compounds are more reactive to the palladium catalyst than allylic acetates and sulfones.