Bromide as the directing group for β-arylation of thiophenes

Direct β-arylation of thiophene derivatives with bromide as the directing group is diclosed. The reaction is conducted with PdCl2/(p-tolyl)3P as catalyst, silver salt as additive and aryl iodide as coupling partner, affording brominated biaryl compunds as product. Control experiments indicated that presence of bromide group enhances the reactivity of C-H bond, enabling β-arylation. Furthermore, the C-Br bond can be facilely converted to many useful functional groups via versatile cutting-edge methodologies. The mechanistic study suggests that silver salt plays a key role in C-H bond activation step.