Palladium‐Catalyzed C2 or C5 Direct Arylation of 3‐Formylthiophene Derivatives with Aryl Bromides

The system Pd(OAc) 2 /dppb was found to be an efficient catalyst precursor for the direct arylation of 3‐formylthiophene derivatives. When using 3‐formylthiophene, the 2‐arylated thiophenes were obtained with regioselectivities of 76–86 %, whereas the arylation of 3‐formylthiophene diethyl acetal gave the 5‐arylated thiophenes with regioselectivities of 64–88 %. These reactions were performed by using only 0.1 mol‐% of the catalyst. Moreover, this procedure has been found to be tolerant to a variety of functional groups on the aryl bromide such as formyl, propionyl, benzoyl, nitrile, or nitro.