Synthesis of Sulfur-Hybridized Pyracylene and the Unexpected Phenyl Shift Mediated Rearrangement of Scholl Reaction

We present herein a strategy towards the straightforward synthesis of a novel sulfur-hybridized pyracylene, tetraceno[5,6-bc:11,12-b'c']dithiophene (TDT) derivatives, via 2-fold FeCl₃-mediated Scholl reaction. Surprisingly, the substituents on the precursors will guide the synthetic route, when the substituents were bromo- or phenyl-, quantitatively debromination or phenyl ring shift mediated rearrangement were observed respectively, the rearrangement products were identified by the HR-Mass and 2D NMR analyses. Additionally, a retrosynthetic method was adopted to confirm the unexpected reaction results in rearrangement of Scholl reaction.