Dithieno[3,4‑<i>b</i>:3′,4′‑<i>d</i>]thiophene-Annelated Antiaromatic Planar Cyclooctatetraene with Olefinic Protons

Abstract

The design and synthesis of a new planar cyclooctatetraene (COT) with protons directly connected to the COT ring was attained by monoannelation with dithieno[3,4-<i>b</i>:3′,4′-<i>d</i>]thiophene. The planar structure of the COT core was unambiguously confirmed by X-ray crystallography. The magnetic antiaromaticity of the COT core was found to be higher than that of the previously synthesized planar COTs with olefinic protons, according to the results of ¹H NMR and absorption spectra as well as NICS calculations