Palladium-Catalysed Intramolecular Direct Arylation of 2-Bromobenzenesulfonic Acid Derivatives

A palladium-catalysed intramolecular direct arylation of 2-bromobenzenesulfonic acid derivatives was found to proceed using 1 mol% of palladium acetate as the catalyst. The influence of the substituents on the phenol moiety of 2-bromobenzenesulfonic acid phenyl esters reveals that electron-donating substituents favour the reaction while electron-withdrawing ones are unfavourable. The reactivity of sulfonamides was also studied and, in all cases, a selective activation at sp2 C?H vs. sp3 C?H was observed. A sulfonamide bearing both phenyl and benzyl substituents on nitrogen gave selectively the six-membered ring product.