Palladium-catalysed direct heteroarylation of bromobenzenes bearing SO2R substituents at C2 or C4

International audiencePalladium-catalysed direct arylation of 4- or 2-bromobenzenesulfonic acid derivatives in the presence of a variety of heteroaromatics was found to proceed using 0.1-0.5 mol% palladium acetate as the catalyst. However, both the nature and position of the SO2R substituent on such bromobenzenes has an influence on the reaction rates and yields. The presence of SO2Et or SO2NEt2 at the C2 or C4 position of bromobenzene is tolerated. Good results were also obtained from bromobenzene substituted at C4 by SO2NHPh or SO2OPh. On the other hand, the reactions of bromobenzenes bearing either SO2N(Me)CH2Ph or SO2OAr at C2 led in some cases to intramolecular reactions instead of the desired intermolecular couplings. Some reactions were performed in cyclopentyl methyl ether, which can be considered as a green solvent