Pd-catalyzed direct C-H arylation of thieno[3,4-c] pyrrole-4,6-dione (TPD): a step-economical synthetic alternative to access TPD-centred symmetrical small molecules

We demonstrate a step-economical and viable synthetic alternative to access a series of thieno[3,4-c] pyrrole-4,6-dione (TPD)-based pi-conjugated molecules through Pd-catalyzed direct C-H arylations. A comprehensive synthetic study including the screening of various kinds of palladium catalysts, ligands, and bases is reported. Under the optimum reaction conditions, TPD and its common derivatives underwent efficient and mild direct C-H arylations with a variety of functionalized bromoarenes. Functional groups such as ester, nitrile, ketone, aldehyde, and halide were well-tolerated, which substantially extended the reaction scope. We hope the reported method will provide materials scientists a relatively greener synthetic route to efficiently prepare TPD-containing pi-functional materials.