Diversity-oriented approach to functional thiophene dyes by Suzuki coupling-lithiation one-pot sequences†
Functional thiophenes, e.g. for organic metal-free dye sensitized solar cells (DSSC), are accessible efficiently via a divergent and diversity-oriented synthetic strategy. Here, we present two straightforward, modular and comparative one-pot syntheses of diversely functionalized thiophenes with high yields starting from simple molecules, namely Suzuki-Lithiation–Formylation-Knoevenagel (SLiForK) sequence and Suzuki-Lithiation–Borylation-Suzuki (SLiBS) sequence. These methods open new avenues to interesting thiophene structure motives with potential applications as pharmaceutical active agents or in molecular electronics, which we have elucidated by a substance library of 21 diversely, mostly unsymmetrically substituted thiophenes. Finally, three novel DSSC dyes were synthesized according to the developed one-pot protocols. For illustration, DSSC devices sensitized by the selected dyes revealed promising solar cell performances, which were rationalized by photophysical and electrochemical characterization and DFT calculations.