5]Radialene with quintuple4 ,5-benzo-1,3-dithiol-2-ylidenes (DTs) easily forms as table polycationic salt (1) 4 + (BF 4 À ) 4 owing to its aromatic characteri nt he central cyclopentadienider ing. In this work, it was found that the polycationic salt (1) 4 + underwent ah ydration reactioni nm oist polar solventt og ive several unexpected products, namely, an oxygen adduct dicationic salt (2) 2 + ,atetrathiafulvalene (TTF) vinylogue( 3)w ith 1,4-dithiine-2(3H)-one moieties, and an oxygen adduct of p-extended TTFw ith ac yclopentenone core (4). Their molecular structures were fully determined by X-ray crystal-structure analysis. In this reaction,irreversible hydration to the polycationic salt might either initiate the ring expansion and lead to the successive hydrationa tthe specific cationic DT ring (for 3), or promote the transannular reactions to the next DT ring followed by elimination of the DT ring (for 4). Cyclic voltammetry and differentialp ulse voltammetry measurements for compound 3 indicated the occurrenceo fm ulti redox process resulting from electronic delocalization on the vinylogous TTF moiety.T he electronic structures of the cationic species of 3 were also investigated by electronic spectra.[a] Dr.Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Hydration reaction of tetracationic salt of [5]radialene bearing quintuple 4,5‐benzo‐1,3‐dithiol‐2‐ylidenes provided some unforeseen oxygen adducts: a transannular dicationic salt linked by oxygen atom; a tetrathiafulvalene vinylogue with 1,4‐dithiine‐2(3H)‐one moieties; and a π‐extended tetrathiafulvalene with cyclopentenone core. The nucleophilic addition of H2O to [5]radialene depends on the structural feature of the π‐conjugated polycationic [5]radialene scaffold. More information can be found in the Full Paper by T. Shirahata, Y. Misaki, et al. on page 4984.

Molecular and crystal structures of dicationic tetrakis(1,3-benzodithiol-2-ylidene)cyclopentanone (1b), (1b2+)2(ReO4−)4(CH3CN)3(H2O)0.7, were successfully determined by X-ray single-crystal diffraction. It was suggested that two 1,3-dithiol-2-ylidenes adjacent to the carbonyl group were effectively conjugated with each other. The remaining two 1,3-dithiol-2-ylidenes, where two positive charges were mainly distributed, were considerably twisted from the central five-membered ring.