Transition-Metal-Free Synthesis of C3-Arylated Benzofurans from Benzothiophenes and Phenols

We report a transition metal-free synthesis of benzofurans from benzothiophenes and phenols that exploits the unique reactivity of sulfoxides. Through a sequence involving an interrupted Pummerer reaction and [3,3] sigmatropic rearrangement, phenols can be combined with readily accessible yet synthetically unexplored benzothiophene S-oxides to provide C3- arylated benzofuran products. The products from this approach can undergo subsequent functionalization to gain access to a range of important benzofuran derivatives.