Thermally stable bisdehydro[12]- and tetrakisdehydro[16]annulenes with planar structures were successfully synthesized by fusion with two dithieno[3,4- b:3',4'- d]thiophene units. The planarized [4n]annulene cores induced substantial antiaromaticity. However, the HOMO-LUMO gap slightly increased as the π-core expanded from the planar cyclooctatetraene. This phenomenon, in contrast to that of typical π-conjugated systems, was attributed to the decrease in antiaromaticity of the [4n]annulene cores. Both TD-HF and GIAO-HF calculations supported this conclusion.

One‐electron and peracid oxidations of dithieno[3,4‐b : 3’,4’‐d]thiophene cyclic dimer, which contains an antiaromatic planar cyclooctatetraene (COT) core, were conducted. The reaction of the cyclic dimer with SbCl5 produced isolable radical cation salts. Density functional theory (DFT) calculations showed that the spin density of the radical cation resides not on the COT ring but on the peripheral sulfur and carbon atoms in the thiophene unit with retention of high antiaromaticity based on the nucleus‐independent chemical shift (NICS). The peracid oxidation of the cyclic dimer was found to proceed not on the COT ring but on the bridging sulfur atom in the dithienothiophene moiety. The retention of the high antiaromaticity of the COT ring after the sulfoxide formation was experimentally confirmed based on the relative hardness, and also was theoretically supported by NICS calculations. Interestingly, the DFT calculations suggested that the high antiaromaticity does not enhance the reactivity towards the epoxidation on the COT ring.

The cover feature shows how the high antiaromaticity of the planar cyclooctatetraene core in a dithieno[3,4‐b:3’,4’‐d]thiophene cyclic dimer is retained during one‐electron and peracid oxidation reactions. Inspired by a counterclockwise base‐run in baseball, the picture shows how the “run” in this study was the formation of the sulfoxide species that has a negative relative hardness and a paratropic ring current (typically shown in a counterclockwise direction). Details are given in the Full Paper by T. Nishinaga and co‐workers on page 704 in Issue 6, 2019 (DOI: 10.1002/cplu.201900064).