Functionalized benzothiophenes are important scaffolds found in molecules with wide ranging biological activity and in organic materials. We describe an efficient, metal-free synthesis of C2 arylated, allylated and propargylated benzothiophenes. The reaction utilizes synthetically unexplored yet readily accessible benzothiophene S-oxides and phenols, allyl- or propargyl silanes in a unique cascade sequence. An interrupted Pummerer reaction between benzothiophene S-oxides and the coupling partners yields sulfonium salts that lack aromaticity and therefore allow facile [3,3]-sigmatropic rearrangement. The subsequently generated benzothiophenium salts undergo a previously unexplored 1,2-migration to access C2 functionalized benzothiophenes.