Superelectrophilic-initiated C−H Functionalization at the β-position of Thiophenes: A One-Pot Synthesis of trans-stereospecific Saddle-shaped cyclic compounds

Superelectrophilic-initiated direct C–H functionalization of thiophenes at the β-position was developed. A series of trans-stereospecific [2,1-a]-IF-thiophene-fused cyclic compounds (4) with saddle-shaped structure were prepared in 17–30% yields through a one-pot superelectrophilic Friedel–Crafts reaction of dihydroindenofluorene with thiophene derivatives. From the crystal packing analyses of 4a, its skeleton shows both strong intermolecular π–π stacking and C–H···π stacking. Furthermore, the ring-dependent photophysical properties of 4 were confirmed by UV–vis absorption and photoluminescence spectroscopy as well as through the study of their fluorescence quantum yield.