Abstract
The superacid-induced condensation of o-methylsulfinylated thiophenyl(ene) compounds under dilute conditions induces an intramolecular electrophilic ring-closing reaction of a hydroxysulfonium cation onto the adjacent benzene ring to yield the thianthrenium ring systems, which disclose π electron delocalization over sulfonio linkages demonstrating the efficacy of planarization of the benzene rings for the p-π/d-π interaction in arylsulfonium moieties. Crystal structure of the thianthrenium salt reveals that the S+–C(phenyl) bond is significantly shortened upon the ring closing as a result of the increased bond order by the resonance effect.
Acknowledgments
This work was partially supported by a Grant-in-Aid for Scientific Research (No. 14703029) from MEXT, Japan.