New synthesis of benzo[1,2-b:4,5-b']dithiophene (BDT)

Thiophene-containing polycondensed aromatic compounds are important source of functional organic materials for different applications. Within this class of molecules, benzo[1,2- b:4,5-b']dithiophene (BDT, figure 1) is recognized as one of the most successful building blocks in the synthesis of highly efficient photovoltaic and semiconducting materials.1 In fact the rigid and planar conjugated structure of BDT makes it attractive for achieving highly tunable molecular energy levels and optical band gaps as well as high hole mobilities. In recent years, benzannulation and thieannulation approaches, involving several steps, have been applied to the synthesis of BDT and of pi-extended thienoacenes,2 but the search of alternative easy access to this class of heterocycles is always a valuable synthetic target. We present here a new two-step synthesis of BDT, starting from 3-thiophene carbaldehyde as unique thiophene precursor.