Unsymmetrical diaryl sulfones and aryl vinyl sulfones through palladium-catalyzed coupling of aryl and vinyl halides or triflates with sulfinic acid salts

The palladium-catalyzed reaction of sulfinic acid salts with a wide variety of aryl and vinyl halides or triflates provides unsymmetrical diaryl sulfones and aryl vinyl sulfones in good to excellent yields. The reaction is strongly influenced by the presence of (Bu4NCl)-Bu-n, and the use of Xantphos, a rigid bidentate ligand with a wide natural bite angle, was found to be crucial for the success of the reaction. With neutral, electron-rich, and electron-poor aryl iodides best results were obtained by using Pd-2(dba)(3), Xantphos, Cs2CO3, and Bu4NCl, in toluene at 80 degreesC. Two general procedures were employed with aryl bromides and triflates: sodium p-toluenesulfinate, Pd-2(dba)(3), Xantphos, Cs2CO3, 120 degreesC, in toluene with (Bu4NCl)-Bu-n (procedure A: neutral, electron-rich, and slightly electron-poor aryl bromides or triflates) and without (Bu4NCl)-Bu-n (procedure B: electron-poor aryl bromides or triflates). With vinyl triflates best results were obtained at 60 degreesC omitting (Bu4NCl)-Bu-n.