Trisulfur Radical Anion as the Key Intermediate for the Synthesis of Thiophene via the Interaction between Elemental Sulfur and NaO<i>t</i>Bu

A facile base-promoted sulfur-centered radical generation mode and a single-step protocol for the synthesis of thiophene derivatives using 1,3-diynes via the interaction between elemental sulfur and NaO<i>t</i>Bu has been reported. EPR experiments revealed that the trisulfur radical anion acts as a key intermediate of this process. A plausible mechanism has been proposed

Iron-Catalyzed Oxidative C–H/C–H Cross-Coupling between Electron-Rich Arenes and Alkenes

A novel oxidative C–H/C–H cross-coupling reaction between electron-rich arenes and alkenes is established utilizing FeCl₃ as the catalyst and DDQ as the oxidant. Interestingly, direct arylation products are obtained with diaryl-ethylenes and double arylation products are obtained with styrene derivatives, which show high chemoselectivity and good substrate scope. A radical trapping experiment and EPR (electron paramagnetic resonance) experiments indicate that this reaction proceeds through a radical pathway in which DDQ plays a key role in the aryl radical formation. XAFS (X-ray absorption fine structure) experiments reveal that the oxidation state of the iron catalyst does not change during the reaction, suggesting that FeCl₃ might be used as a Lewis acid. Finally, a detailed mechanism is proposed for this transformation